CA2066327A1 - Molded protective exterior weather-resistant building panels and method of making and installing - Google Patents

Abstract

ABSTRACT
Molded exterior building panels formed from thermoplastic material and method of making and installing such panels in aligned relationship on building structures. An upper margin of a building panel includes nail slots for fastening to a building. An upwardly projecting lip along the top defines an engageable mounting groove behind this lip.
horizontally extending mounting hook on the back of a lower margin of each panel provides for hooking engagement with lip and groove of a next lower installed panel. During installation such hooking engagement advantageously supports the weight of a panel being installed and automatically provides alignment of the panel with the next lower installed panel, thereby freeing an installer from the burden of holding a panel in a desired position at a desired level while driving nails through the nail slots. Panels are molded from thermoplastic material with surface textures and patterns for simulating courses of attractive building surfacing products, such as clapboards, shingles, shakes and slates. Front and back lap-joint channels are routed along panel ends. The mounting hook is formed by heating, bending down and then setting a rear edge of a horizontally-extending, rearwardly-projecting ledge strip.
Elongated nail slots accommodate thermal expansion and contraction of installed panels. Anti-overdrive ridges above and below the nail slots prevent driving nails so tightly as to restrict expansion and contraction. Wider multi-course panels may have a second horizontally-extending, intermediately-located mounting hook on the back for engaging a locking strip.

Description

D PR()TECT:[VE E)~I~IOR WE~ R-RESIS~' BUILDI~ P~S AND METE~OD
OF M~KI~ AND INSq~LLI~æ

_IELD OF THE INVENTION
The present inventio~ is ln the field of protective, weather-resistant p nels for exterior side walls and end walls and sloping roofs of building structures, such as residential, commercial and industrial structures. More particularly, this invention relates te conveniently attachable, self-aligning protective molded exterior building panels configured to look like clapboards, shingles, shakes or slates for installation on side walls, end walls and sloping roofs of buildings an~ relates to the method of making and installing such exterior weather-resistant panels.

~ACKGROUND
There are about fifteen materials which have been used traditionally for exterior protective surfaces on residential and industrial ~tructures. Brick was a leading siding material for many years. Other siding materials have been favored for use in certain geographic regions. For example, stucco primarlly has found significant usage for new construction in the southern and we tern regions of the ~nited States.
Currently, aluminum, hardboard, plywood and vinyl panels have dominated the siding market because of their affordable cost and lower maintenance as compared with brick or stucco. These four matexials have been fabricated to simulate the shape and tex~ure of the classic clapboaxds, wood shakes and 2 ~

shingles that consumer~ prefer. Sla~tes have also been a classic surface matexial for residential roofing in some geographlcal areas, but slate rooflng currently is expensive. The shapes and textures of such classic exterior surface materials produce attractive patterns of highlights and shadow lines on walls and roofs as the sun shifts in position during daylight.
Extruded clapboard-pattern vinyl ~iding has been found to offer a number of advantages over other siding materials. It will not crack, chip or peel. Vinyl, i. e. polyvinyl chloride (PVC), siding never needs paintins, as the colorants added during production permeate the siding material. Also, vinyl siding will not rust, dent, rot or host termites or carpenter ants. Vinyl siding is relatively light in weight (comparable in weight to aluminum siding) which makes it easy to handle by the applicator. Because vinyl does not conduct electricity, it does not require electrical grounding.
Extruded clapboard vinyl siding's main disadvantages are caused by a high coefficient of thermal expansion and contraction and by a width limitation of prvfile e~truded vinyl siding, which is limited to about fourteen inches. "Oil canning1' caused by temperature changes tends to occur in long lengths of vinyl siding. In order to accommodate thermal expansion and contraction and to achieve the desired protective coverag~, an installer will often overlap the vertical edges of vinyl siding, causlng noticeable unattractive ou~ward bends in 2~327 the Pnds of the overlapping end po~:ions of such siding.
Conventional vinyl siding has an unattractive or unnatural softness or ~Igive~ to the touch because extruded vlnyl areas less than about 0.100 of an inch in thickness are unduly flexible compared with the rigid nat:ure of wood, stone, brick or stucco.
Because of its flexibility, extruded vinyl siding is limited in the width of clapboards which can be simulated. A
ten-inch-wide-face board is not simulated by a conventional vinyl extrusion. Six inches is th~ widest face board simulated by a vinyl extrusion in my experience. ~hus, a vinyl extrusion eight inches wide simulates two four-inch board~, and one ten inches wide simulates two five-inch boards in order to obtain some stiffening effect by a ~haping o~ the vinyl material between the two simulated boards. Against this background, it is noted that in Western regions of the ~.S. a ten-inch or a twelve-inch clapboard siding width is popular for home surfaces.
Extruded vinyl siding often has a hand-tooled synthetic-appearing graining which is rolled into the extruded product after a partially congealed (solidified) "skin" has formed on the extruded product, thereby reducing the sh~rpness of the impressions in this solidified skin. Such a synthetic-appearing graining repeats itself at frequent intervals along the length of the vinyl siding. This frequent repetition is caused by a relatively short circumference around the hardened-steel roller die on which the graining pattern was initially hand-tooled by a die maker.
The prior art production methods of extruding and then roll-forming vinyl siding can only produce lineal shapes of such siding.

SUMM~RY
The present invention provides molded exterior weather-resistant panels made of thermoplastic material. For example, panels for simulating one or more courses of clapboards, shingles, shakes or slates may be molded from vinyl so as to retain all of the advantages of vinyl while overcoming or substantially reducing the problems described above, which have been inherent in the prior use of extruded vinyl material for siding.
; The molded protective exterior weather-resistant building panels embodying the present invention may be molded using other suitable thermoplastic materials and may be molded as a composite or laminate of two or more thermoplastic materials. Advantageously, such building panels may be molded in any desired length in the range from a few feet up to twenty feet or more, and such building panels may be molded in any desired width up to forty-eight inches or more, as may be desired for various building applications and may be molded to simulate one or more courses of clapboards, shingles, shakes or slates.

3 ~ ~

As used herein, th~ term nth~rmoplastic material" is lntended to mean thermoplastic pol~er resins and/or thermoplastic copolymer resins which may or may not contain ingredients and/or addltives including, but not limited to, colorants, reinforcing particles, reinforcing fibers, reinforcing fabric layers, laminates, surfacing layers, foamants, anti-oxidants, fillers and/or other ingredients and/or additives for enhancing performance of a molded exterior building panel madP therefrom. Vinyl (PVC) is a ~hermoplastic matexial.
~ s used herein, the term "rearwardly" or "rearward"
means inwardly or inward toward the wall structure or roof structure, as the situation may be. The term "forwardly" or "forward" means outwardly or outward from such building structure.
In accordance with the invention, exterior weather-resistant building panels are provided molded from the~moplastic material. These exterior building panels are attractive in appearance and are adapted to be installed on side walls, end walls and sloping roofs of buildings, including residential, commercial and industrial buildings for protecting building structures ~rom weather. Each such exterior building panel has an upper margin, a lower margin and a main area extending between the upper and lower margin. The upper margin is adapted for attachment to a wall structure or suitably 510ping roof structure of a building and is arranged to be 2~32~

overlapped and hidden by a lower margin of a next adjacent higher course of the exterior building panels.
For enabling con~enient installation of the next successive higher course of these panels, the top edge of the upper margin of a panel is shaped to provide an upwardly facing groove. For example ,the top edge is positioned a slight distance away from a wall structure or roof structure to ~hich the upper margin of the panel is attached for defining a groove between the top edge and the building structure. Extending along the back of each panel at the juncture of the main area and the lower margin, is a horizontal rib protruding rearwardly (inwardly toward the building structure) and having a downturned lip for providing hooking means engageable into the upwardly facing groove of the next adjacent lower panel.
The installer ~uickly and easily engages the downturned hooking lip of an exterior building panel embodying the invention into the upwardly facing groove provided by the next adjacent lower course of panels. Thu~, the panel being installed becomes aligned with and supported by the next adjacent lower course of panels. Moreover, the hooking engagement between this hooking lip and the groove prevents the lower margin of the panel being installed from moving outwardly, i. e. fro~ being blown away from its hooked position on the building.

~6~327 After the installer has done this hooking engagement of a panel, the installer then attaches the upper margin of the panel to the building by fasteners, such as nails, being driven through a row of slotted openings e~Pnding horizontally along the upper margin. These slotted openings (nailing slots) are elongated in the horizontal direction for accommodating thermal expansion and contraction of the elongated panel in the horizontal direction. For preventing fasteners, such as nails, from being driven so tightly that their heads would prevent longltudinal thermal expansion and contraction of the pamel, the row of slotted openings is recessed relative to nearby regions of the upper margin. Por example, a pair of parallel, longitudinal ridges extend horizontally along the upper margin.
These ridges are positioned above and below the row of slotted openings. These ridges are spaced suf f iciently far apart for recei~ing a nail head between them but not so far apart as to allow a hammer head to enter between them. Thus, the nail head cannot be driven too tightly and will not restrict thermal expansion and contraction of the panel Also, this pair of parallel ridges provides increased lineal stiffness in a building panel.
In an illustrative embodiment of the invention, the main area and lower margin of the exterior building panel are inclined outwardly in a downward direction for simulating a selected configuration of an exterior building surface such as 2 0 ~

one of the exterior surfaces comprising one or more courses of clapboards, shlngles, shakes and slates.
In lllustrative embodiments of the invention, the main area and lower margin of the molded panel are stiffened by reinforcing ribbing integrally molded on the back, and the rib providing the hooking lip i~ integral with such reinforcing ribbing and extend~ rearwardly beyond such ribbing. The hooking lip is shown spaced rearwardly from the reinforcing ribbing for providing hooking engagement as shown. ~ second hooking lip may be provided positioned in an lntermediate location on the rear of a wider panel designed for representing multiple courses of surface material.
For convenience of description, the illustrative exterior building panels embodying the invention are described as the panels are illustratively shown oriented in an installed position on a vertical wall 3tructure of a building, or on a suitably sloping roof structure of a building with the elongated panel extending horizontally along such building structure.
Thus, such hori20n-~riented term~ as "hori~ontal~, "horizontally", "vertical", "vertically", ~upper", "upwardly", "lower", "downward", "downwardly", "top" and "bottom" are not intended as being llmiting of the claimed invention but rather such term~ are used as easily understood, conveniently descriptive wordinq relating to an exterior building panel embodying the inven~ion when such a panel is oriented in a 20~63~

position such as lt would occupy in .lnstallation on a v~rtical wall structure or sloping roof structure.

BRIEF DESCRIPTION OF THE DRAWINGS
The invention, together with further objects, aspects, advantages and features thereof, will be more clearly understood from a consideration of the following descrlption in conjunction with the accompanying drawings in which the same elements bear the same reference numbers throughout the various FIGUR~S.
FIGURE 1 is a perspective view of an exterior sid~ wall and an exterior end wall and a sloping roof, being shown as portions of a building, such as a house, covered by molded panels embodying the present invention. For purpose of illustration, different style6 of panels have been shown on th~
walls. Upper courses are shown as wood grAin textured clapboard surfaces; other courses are shown having smooth clapboard surfaces; and areas of panels on the walls are shaded to indicate shingles or shakes, as the case may be. Also, for purposes of illustration, areas of panels on the roof are shaded to indicate any of ~hingles, shakes or slates, as the case may be.
FIG. 2 is an elevational sectional view of the exterior wall and sloping roof of FIG. 1 taken along the line 2-2 of FIG.
1.

~66~2~

FIG. 3 is an enlarged elevational sectional view of a lower portion o~ the exterior wall or roof of FIG. 1 taken along the wall line 3-3 or the roof line 3'-3'. FIG. 3 shows the use o a "starter strip" located at the bottom edge of the wall or roof structure for beginning application of the courses of molded building panels. For purposes of explanation, FIG. 3 shows a hammer head in the action of nailing the upper margin of a third course of the molded panels to the building structure.
FIG. 4 is a further enlargement of an upper portion of FIG. 3 for illustrating in detail features of the invention.
The nail slot area is recessed about one-sixteenth o~ an inch for preventing nailing too tightly, for avoidance of undesired restriction of ther~al expansion and contraction.
FIG. S is a front elevational view, as seen from the position 5-5 in FIG. 3, ~howing a portion of a molded building panel and showing broken away portions of the underlying structure of the building.
FI&. 6 i8 a view similar to FIG. 5, except that a textured surface i6 indicated on the molded building panel~.
Also, FIG. 6 shows a joint between the ends of two adjacen~
molded panels in the same course. FIG. 6 also shows the use of sheathing between a water-barrier layer and wall studs or roof rafters; whereas FIG. 5 shows a light-weight wall construction arrangement where molded panels are attached to studs without using sheathing betwe~n the water-barrier layer and studs.

3 2 ~

FIG. 7 i~ an enlarged ~1QVat1Ona1 view of a portion of a lap joint ~etween the ~nds of two bu:ilding panels.
FIG. 8 i~ a view of this lap joint as seen from the bottom looking upwardly in FIG. 7.
FIG. 9 is an enlarged elevational ~iew similar to FIG.
7 illustrating ability of the joint to accommodate dimensional changes in the molded building panels due to thermal expansion or cont.raction.
FIG. 10 is a view of the lap join~ as seen from the bottom looking upwardly in FIG. 9.
FIG. 11 is an enlarged elevational view of the front of a molded building panel embodying the invention, indicating that any desired three-dimensional pattern may be imprinted on the front surface, for example, patterns selected from the group comprising clapboards, shingles, shakes and slates. FIG. 11 also show~ a row of spaced slotted openings aligned along the upper margin of a molded panel, with a pair of parallel longitudinal flat-sur~ace ridges extending above and below the nail~slotted area for preventing a nail head from beinq driven too tightly. Unduly tight nailing is undesired, because over-driving of nail heads would restrict thermal expansion and contraction. Also, this pair of parallel, longitudinal ridges provides increased lineal stiffness to the upper edge of the panel for helping the installer in handling the pan~l durinq installation. The functioning of these anti-over-drive ridges 2 ~ 2 7 i~ shown in FIG~ 4 ln cooperation wlt~i a hammer head and a nail being driven.
FIG. 12 is a view of the inturned bottom edge of the panel of FIG. 11 indicating that any desired three-dimensional pattern may be molded on this bottom edge.
FIG. 13 is an elevational view of the back surface of the molded siding panel of FIG. 11 for illustrating a square or diamond "waffle" pattern oX inteyral diagonal reinforcing ribbing for strengthening the surface area of this panel.
FIG. 14 is a view of the bottom edge of the molded panel of FIG. 13, showing a portion of the panel surface and an integrally formed reinforcing rib in section, illustrating a triangular sectional shape for such ribbing.
FIGS. 15, 16 and 17 are views showing progres~ive steps in the formation of a down-turned hook-action mounting lip on the inner edge of a rear ledge extending longitudinally along the back surface o~ a building panel embodying the invention and formed of thermoplastic material.
FIG. 18 is a drawing similar to FIG. 4 for illustrating an alternative embodlment of the invention in which a larger hook-engageable lip on the upper edge of a building panel is flush with the front of the upper anti-over-drive ridge for providing a more positive hooking engagement with a larger hooking lip on the next panel.

3 ~ 7 FIG. 19 is an enlarged view similar to the lower portion of FIG. 3 for illustratinq ~n alternative embodiment of the invention in which a wider building panel is molded for attractively simulating two courses of such products as clapboards, shingles, shakes or slates, as the case ~ay be.
FIG. 20 is a drawing similar to FIG. 19 for illustrating an alternative embodiment of the invention in which a considerahly widened building panel is molded to simulate four courses of such products. Also, FIG. 20 shows an installation in which a longitudinally extending, horizontal locking strip is used to attach an intermediate region of such a wide building panel to the underlying building structure~

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In FIG. 1 is shown a building 20 includin~ side walls 22 and an end wall 24, these walls being covered with courses 26 of protective exterior building panels 28 embodying the invention. For illustrating various possible pat~erns and surface-texture configurations of these panels 28, so~e of the upper courses 26 on ~he walls are shown to include panels having a wood grain textured clapboard surface 30, while other courses are shown to have a smooth clapboard surface 31, and also areas of panels on the walls are shaded at 33 to indicate that these panels may have patterns and surface texture configurations tc look like shingles or s~akes, as the case may be in any particular building in~tallation.

2 ~ 2 7 A concavQ corner o~ the bullding between two side walls 22 is covered by a concave vertical txim strip 3~. ~ convex vertical trim strip 34 covers a convex wall corner between end wall 24 and a side wall ~2.
The roof as shown is suitably sloping and is covered with courses 26 of protective exterior building panels 28 embodying the present invention. For example, the shading at 35 indicates that these building panels 28 may have patterns and surface texture configurations to look like shingles, shakes or slates, as ~he case may be, in any particular building installation. It is to be understood that the panels 28 are not designed for installation on a flat roof nor on a gently sloping roof because of weather considerations. A suitably sloping roof ha~ a pitch which is su~ficiently staep for enabling the panels ~8 to resist intrusion of wind-driven rain. Generally, a roof which is sufficiently pltched for appropriate installation of shingle in a particular geographic area under local weather conditions is suitably sloping for installation of the panels 28~
Shown in FIG. 2 is a portion of the frame structuxe of the building 20 comprising a roof rafter 36 , a ceiling joist 38, and a wall stud 40, with horizontal double-top plates 42 and a bottom horizontal plate or ~shoe" 44 mounted on a footing or foundation 43. The top and bottom plates 42 and 44 interconnect top and bottom ends of wall stud~. Such studs 40 may be made 2~327 .

from wood, a~ indicted ln FIGS. 3, 5 and 6, or may be made from aluminum channels or steel channels, or other structural, load-supporting members suitable for use in a wall structure 45.
Such roof rafters 36 may be made of wood, as indica~ed in FIGS.
3 and 6, or may be made from aluminum channels cr steel chann~ls, or other st~lctural, load-carryinq members suitable for use ln a roof structure 47.
In FIGS. 2, 3 and 6, the wall structure 45 and roof structure 47 are shown as including a sheathing layer 46, for example a layer of plywood or particleboard, or a similar suitable stiff structural layer. This sheathing lay~r 46 is shown secured to studs 40 and to the top plates 42 and to the bottom plate 44. In the roo~ tructure 4~ this sheathing layer 46 i5 shown ecured to ra~texs 36. Over the sheathing layer 46 is a moisture-permeable water-barrier sheet layer 4~, for example, comprised of asphalt-impregnated building felt paper or of "TYVEX" (brand) housewrap material commercially available from du Pont Corporation, or the like. The building panels 28 are fastened to the ~heathing layer 46 and/or fastened to the wall studs 40 or to the roof rafters 36.
The panel~ 28 are arranged ln horizontally extending courses 26 with lower margins of panels in a next ad~acent higher course in hook engagement with and overlapping and covering upper margins of panels below them.

2 ~ 2 7 In FIG. 3 a hammer head 50 is shown driving a nail fastener 52 for fastening an upp~r margin of a third-course panel 28 to a building structure. In this illustrative example, the nail 52 passe~ through water-barrier and sheathing layers 48, 46, respectively, into a stud 40 or into a roof rafter 36.
Other nail ~asteners 52 are shown similarly attaching upper margins of second and first courses o~ the panels to the building structure 45 or 47. The courses of siding panels are installed on a wall structure ~S or on a roof struc~ure 47 by starting at the bottom edge of the wall or roof and then by progressing upwardly fastening each successive higher course.
In order to start installing the lowermost (first) course 26, a starter strip 54 (FIG. 3) is first fastened to the wall or roof structure 45 or 47, for example, by using nail fasteners 52.
Then, the lower margin of the lowermost panel 28 is aligned with and is held in place by hooking engagement with this starter s~rip 54, as will be explained in detail later.
Inviting attentlon to FIGS. 4, 11 and 12, an e~terior building panel 28 molded from thermoplastic material and embodying the invention comprises: an upper m rgin 56, which may also be called a "naillng strip", a lower margin 58, and a main median area 60 extendlng between the upper and lower margins.
Such a panel 28 may have any desired width (including the upper and lower margins 56 and 58, together with the median area 60) in a range up to forty-eight inches, or even more, dependin~

upon the number o~ course~ o~ aurface material represented by the panel and depending upon the width of each course being represented, as will be e~plained later. Such panels 28 may have any desired suitable horizontal length 'IL" (FIG. ll), for example, being 6, 8, lO, 12, 14, 16, 18 or 20 feet in length or more or less. The upper margin 56 is shown having a flat back side 62 (FIG. 4) for facing toward and fastening against a wall or roof structure 45 or 47, respectively, as the case may be..
Extending along the top edge 64 of the upper margln 56 is an upwardly projecting lip 66 which i~ spaced forwardly from the bac~ side 62 for defining an upwardly-facing, horizontally-extending mounting groove (or "slotn) 68 which is adapted to be used for hooking-action attachment of a lower margin o~ a next upper panel, as explained in detail later. It is noted that the insida (rear) surface of the lip 66 slope~
rearwardly in a downward direction for providing a rearward camming (wedging) action during such hooking engagement of a next higher panel.
In order to attach the upper margin ("nailing strip") 56 of a panel 28 to a wall or roof ~tructure 45 or 47, there is at least one row of mounting apertures 70 (FIG. ll), which may be called "nailing ~lots", spaced downwardly from the upper edge 64 and extending horizontally. In the ~olded exterior building panel embodiment of the invention shown in FIGS. 4, ll and 13, this row o~ mounting apertures 70 extends horizontally along the 2~3~ 7 centerline of the upper ~argin 56.
For accommodating thermal expansion and contraction of the horizontally elongated panels 28, these mounting apertures (slots) 70 have a vertical width wider than the shank of a nail fastener but narrower than a nail head. For e~ample, the vertical width of these nailing slots 70 is in a range from about 5/32n~s to about 7/32nds of an inch, and they are horizontally elongated, or example having a horizontal length in a range from about O.6 of an inch to about 2.5 inches, depending upon the panel length L (FIG. 11~. The longer the panel length, the longer these nailing slots are preferred to be for accommodating thermal expansion and contraction. These nailing slot~ are shown spaced about one-half to three-quarters of an inch apart. In a presently praferred embodiment, these nailing ~lots 70 have a vertical width of about 3/16ths of an inch, and they have a length of abol~t one inch for a panel having a length up to about ten faet. Such one-inch long nailing slots are shown spaced apart by a spacing of about 1/2 inch, because wall ~tuds 40 or roof rafters 36 often have a horizontal width of about 1.5 inches. For panels longer than ten feet up to about twenty feet, the length of these nailing slots is preferred to be ln the range of about l.S to about 2.5 inches. These presently preferred dimensions provide an installer with facillty for driving fasteners 52 through appropriately selected apertures 70 into the studs 40, as shown 2~327 in FIGS. 3, 5 and 6 or into raftQrs 36, as shown ln FIGS. 3 and 6.
In these illustrative examples, the nail fasteners 52 are shown having relatively large diameter flat heads 69, sometimes being called "rooflng nails". For assuring that the elongated mounting apertures 70 will accommodate horizontal thermal expansion and contraction, anti-over-drive means are provided for preventing the nail heads 69 from being driven so tightly that they would grip or crimp the perimeters of the apertures, thereby preventing expansion and contraction. Such anti-over-drive means as shown comprises recessins the nail slot region 74 (FIG. 11) by an amount slightly more than the thickness of tha flat heads on nails 52.
This recessing of the nail-slot region 74 is shown being provided by two flat-surfaced ridges 71 and 12 positioned above and below the nail-slot region. These parallel ridges are located respectively equal distance~ above and below the row of apertures 70. As shown in FIG. 4, these longitudinally extending ridges 71 and 72 are about 1/16th of an lnch in front-to-bacX extent and are sufficiently widely spaced "S"
(FIG. 11) for receiving the flat head 69 of a "roofing nail" 52 between them, but thay are ~ufficiently closely spaced for preventing a hammer head SO from entering between them. For example, this spacing "S" is in the range from about 5/8ths to 3/4ths of an inch. Consequently, there advantageously remain~ a 2~327 slight clearance hetween tha head 69 of a driven nail fastener 52 and the nail slot region 74 beneath the nail head. Each nail head thereby becomes driven into substankially the same closely spaced relationship with respect to the nail slot reyion 74 between ridges 71 and 72 for firmly holding the back ~ide 62 of the upper margin against the wall or roof structure ~5 or 47 with sufficient clearance remalning beneath the nail head for allowing thermal expansion and contraction to occur for the length L of the whole panel 28.
The vertical width of the upper margin 56 as seen in FIG. 11 may be in a preferred range of about ~-3/4 of an inch to about 3-1/2 of an inch and may be in a more preferred range fro~
about 2 inches to about 3 inches, for example being about 2-1/2 inches in vertical width. The vertical width of the lower margin 58 as seen in FIG. 11 is sufficient for providinq attractive and weather protective coverage when installed over the upper margin o~ a next lower panel, as shown in FIG. 4.
Thus the width of the lower margin 58 is preferred to be qlightly greater than ths width of the upper margin 56 for providing the desired overlapping coverage over the upper margin of an adjacent lower panel.
The lower margin 58 terminates at the bottom in an inturned bottom edge 75 forming a rear flange which extends rearwardly a sufficient distance "B" (FIG. 4) for substantially reachinq tha front face of the ad~acent lower panel for 2~327 simulating wood clapboards, shingles, shakes or slates as may be desired. For example, the bottom dimension "~" is in a preferred range from about 1/2 inch to about 1-1/2 inches and is more preferred to be in the range of about 5/8 inch to about 1-1/8 inches, for example being about 0.71 of an inch for simulatlng a wood clapboard, shingle, shake or slate product having a butt thic~ness of ahout 3/4ths of an inch.
In FIG. 4 ls shown a panel 28 for simulating one course 26 of surface matsrial, and t~e main median area 60 and the lower margin 58 are shown generally coplanar, extending downwardly and inclined outwardly relative to the flat back side 62 of the upper margin. For example, the average downward outward inclination of the course 26 defined by the main ~edian area 60 and of the lower margin 58 relative to the bacX side 62 is shown in a preferred range from about 3 degrees to about 7 degree~. In FIG. 4, this downward outward inclination of the course 26 is shown as being a more preferred value in a range of a~out 4 degrees to about S degrees.
The main median area 60 and the upper margin 56 are joined along a horizontal juncture region 76 located adjacent to a line of inflection 78 at the upper limit of the downward outward slope of the maln median area 60.
The desired width of the lower margin 5~ for providing protective overlapping coverage of an adjacent upper margin was previously described. In order to simulate clapboards~
shingles, shaXes or sl~tes, the vertical wid~h of the main 2~3~7 median area 60 added to the vertlcal width of the lswer margin 58 may be equal to an overall amount "W" (FIG. 4) comparable with typical exposure to weather of one course 26 (See also FIGS. 1, 2 and 3) o~ wood clapboards or of wood shinglQs or of shakes or of slates, as the case may be, depending upon a desired simulation and in accord with surface textural configurations and patterns 30, 31, 33 or 35 (FIGS. 1 and 6).
For example, in a situation as shown in FIGS. 3 and 4 where each panel 28 represents a single course 26 of surface material, then "W" may be in a preferred range from about 6 inches to about 14 inches and may be in a more preferred range from about 7 inches to about 12 inches, depending upon the exposure to weather of the course 26 of the natural wood or slate product being attractively simulated by building panels 28. Thus, the overall width W' (FIG. 4) of the whole panel 28 including its upper margin 56 may be in a range of about 7-3/4 inches to about 17-1/2 inches depending upon the exposure to weather with W and depending upon the width of the upper margin. It is agaln noted that this panel 28 in FIG. 4 is shown as designed to simulate a single course 26 (FIGS~ 1, 2 and 3) of clapboards, shingles, shakes or slates.
In order to stiffen the main median area 60 and lower margin 58, an integral reinforcing rib~ing 80 (FIG. 13) is shown molded on the back of the panel 28. For example, this ribbing 80 may have a repetitive diamond square or waffle pattern, wherein each diamond is shown as having a diagonal 2~327 co~ner~to-corner dimension in a preferred range of about 2 inches to 4 inches, depending upon the thickness and inherent stiffness of the thermoplastic material, and in accord with desired product characteristics of the main median area ~0 and lower maryin 58. This integral ribbing 80 as shown comprises diagonal ridges 82 each having a triangular cross-sectional shape, as seen in FIG. 14.
As seen most clearly in FIG. 4 and in FIGS. 14 through 17, the entire face region 83 of a panel 28 is shown as having a thickness "Tl' in a pre~erred range from about 5/32nds of an inch to about 3/8ths of an inch, for example being about 1/4th of an inch.
In order to provide hooklng and aligning and weight supporting engagement with an upwardly pro~ecting horizontally extending lip 66 on a next lower panel, as shown in FIG. 4, there i5 a molded rearwardly projecting horizontally extending leg strip 84 (most clearly seen in FIGS. 15 and 16). ~his leg strip 84 is integrally molded generally perpendicular with the face region 83 and is integral with the reinforcing ribbing 80.
This leg strip 84 i6 located at the juncture 85 of the main area 60 and the lower ~argin 58.
A process which may be used for molding thermoplastic material into panels 2~ is disclosed in U.S. Patent No.
4,290,248 in which ~he present inventor is one of the two joint inventors.

2~327 It is preferred that the ~hermoplastic material be foamed during the molding process for producing panels 28 having a density in a preferred range of about 0.7 to about 0.4 of the density of the thermoplastic material prior to such foaming.
The panels 28 as ~hown have a density in a more preferred range of about 0.6 to about 0.45. Among the advantages of such foaming are to reduce weight and cost and to provide an enhanced thermal insulation effect after installation on a wall structure 45 or roof structure 47. Moreover, by virtue of such foaming, a given mass (quantity measured by weight) of the thermoplastic material produces a panel 28 having considerable thicker (dimension "T") overall surface region 83, thereby advantageously increasing panel rigidity as compared with a panel of the same length and width molded from an equal mass of ~nfoamed thermoplastic material. The ribbing 80 further stiffens the panel 28 and increases its rigidity.
In the molding process disclosed in said U.S. Patent No. 4,290,248, a ~old of 25 feet or more in circumference may produce continuous lengths of panel product with no repetition in surface pattern and texture 30 for at least 25 feet. Then, building panels 28 of discrete length "L", for example 8, 10, 12, 14 or 16 feet or more are cut from the continuous molded product having a repeating pattern every 25 feet, thereby producing panels 28 that are rarely identical in surface texture and configuration, a~ compared with prior art extruded and then ; 7 rolled vinyl siding that ~hows the ~ame pattern repeated two to six times on each co~mercial length of siding.
Sub~equent t~ molding of the whole pan~l 28, the rear edge portion of the leg strip 84 is bent down and ~et at about a right angle relative to the unbent portion for forming a hooking flange or lip 86. Such bending down and setting of the hooking flange or lip 86 on the leg strip 84 is accomplished by first heating this leg 84 by impinging jets 88 (FIG. 15) of hot ~ir fed through noæzles 90 aimed at the rear edge portion of this leg. Next, the heated edge portion of this leg 84 is introduced, as shown in FIG. 16, between a flanged anvil roll 91 rotatable around an axis 92 and a forming roll 93 rotatable about an axis 94. Then, the axis of 94 of this forming roll is moved as shown by arrow 95 toward the anvil roll axi~ 92 for initiating forming of hook neans 84, 86. This hooking flange 86 is then roll-formed to provide substantially right-angle hook means 84, 86, as shown in FIG. 17. Following such roll-forming of the hooking flange or lip 86, it is retained in its substantially right-angle bent BtatQ and is cooled by shape retention and cooling means (not shown), for example such as a cooling shoe.
In order to provide for neat convenient lap joint installa~ion of panels 28, the rear surface of each panel 28 is routed as seen in FIGS. 12 and 14 parallel to one cut end (for example, along the right end of each panel) to provide a ~6327 vertically extending rear channel 92, for example, having a horizontal width of about 1 inch for a panel length L up to ten feet or a width ~f about 1-~/2 inches for a panel length over ten feet up to sixteen feet or a width of about 2 inches for a panel length from sixteen to twenty feet, depending upon the type of thermoplastic material from which the panel is made and its coefficient of thermal expansion and contraction, and having a depth of about 1/8th of an inch, with an adjacent vertically extending parallel rear lip 93. The front surface of each panel 28 is similarly routed (for example, the left end of each panel) to provide a front channel 94 having a comparable width and depth with a vertically extending parallel front lip 95. This routing of the channels 92 and 94 and their parallel lips 93 and 95 is accomplished at the same time that the continuous molded product is being cut into discrete panel lengths "L", as was discussed above.
In FIGS. 7, 8, 9 and 10 are shown enlargements of portions of the lap joint illustrated in FIG. 6 for illustrating accommodation to thermal expansion and contraction. For convenience of reference, the respective panels 28 on the left and right are indicted by 28-1 and 28-2. In accommodating thermal expansion, the amount of overlap increases t as shown by a zigzag arrow 96, and only a relatively narrow portion "F" of the routed front channel 94 i5 visible. As a result of thermal contraction, the overlap decreases, as shown by a straight arrow 2~632~

98, and a wider portion "G" of front chann~l 9~ becomes visible. Thus, regardless of expansion or contrac~ion, a neat joint is provided and the underlying wall or roof structure is protected from weather.
In an alternative embodiment shown in FIG. 18, the upwardly projecting lip 66 along the top edge 64 is made relatively larger in vertical extent and in thickness than in FIG. 4 by being molded flush with and integral with the upper anti-over-drive ridge 71. The upwardly-facing, horizontally-extending groove or 610t 68 is also made relatively larger in vertical extent and larger in front~to-back width. By virtue of these increases in size, the hooking flange or lip ~6 on the rear leg strip 84 can be made larger in vertical extent and in thickness for providing a more positive hooking action, i.e. there is an increased firmness of the hooking engagement over and behind the upwardly projecting lip 6S. As explained previously, the inslde (rear) surface of lip 66 slopes rearwardly in a downward direction for providing a rearward camming (wedging ) action on the hooking flange or lip ~6 of the next higher panel. The relatively large vertical extent of this hooking flange 86 provides a strong wedging action behind the lip 66. Except for these described modifications in the top edge 64, rid~e 71 and lip 66, groove 68, leg strip 84 and hooking flange ~6, the panel embodiment 28 of FIG. 18 may otherwise be similar to the panels 28 previously described.

2~6~327 M2rHOD OF INSTALLING
3uring installation of any embodimen~ of the panels 28 on a wall structure 45, or on a roof structure 47, a starter strip 54 is fastened ~long a lower portion of the wall or roof where a hooking flange or lip 86 on a first or lowermost panel is to ~e located. A snap-line horizontal chalk line or other suitable level marking on the wall or roof structure may be used to assure that the starter strip is level (horizontal). This starter strip has an upper lip 66 (FIG. 3) and rear groove adapted for engagement with a ~ooking flange or lip 86 of the lowest panel 28. ~y virtue of this hooking engagement, the lowast panel 28 automatically becomes aligned horizontally wi~h the starter strip 5~ in the desired level position for installation of this first panel. Moreover, this hooking engagement advantageously supports the weight of the lowest panel 28, thereby freeing the installer's two hands for accurately positioning and driving fastener nails 52 through the selected nailing slots 70 in the upper margin of this fir~t panel. In other word6, the installer does not nPed help from another person or from temporary supports or temporary attach~ents in order to keep holding the lowest panel in true level position while driving the fastening nails for permanently fastening its upper margin to the wall or roof structure.
As soon as fastenin~ of the upper margin of the lowest course of the panels to the wall or roof structure has been completed, each next higher overlying panel is placed in hooking 3 2 ~

engage~ent with an upper lip of an ad~acent lowest panel, thereby again automa~ically achie~ing an aligned level position for the cecond course of panels. The upper margins of these next higher panels are fastened to the wall or roof structure after being hooked in position, and then overlying panels for the third course of panel~ are hooked into position and their upper margins are fastened to the wall or roof, and so forth, as the installer proceeds by hooking into alignment and supporting the overlying panel of each successive higher course and then fastens its upper margin.
This hooking engagement method of automatically achieving self-levelling alignment and weight support for installation of each successive higher course of panels facilitates speedy and accurate installation of panels covering a wall or roof, thereby using less time and less labor steps and assures that each course is self-levelled in alignment with the horizontal starter strip. In summary, if the starter strip is fastened level, all of the courses of panels will then become level by their advantageous self-levelling hooked engagement with the successive underlying courses.
If an installer happens to lack enough starter strips 54 and has a surplus of panel~ 28 at hand, additionally needed "starter strips" can quickly and very satisfactorily be made on the site by using a circular saw to cut off upper margins 56 from unused panels. A convenient place to guide the cutting 2~632~

blade iB along the zone between the lower ridge 72 and the inflection line 78.

WIDER BUILDING PANELS SIMWLATING MORE THAN
ONE CO~RSE OF SURFACE MATERIAL

In FIGS. 19 and 20 are shown wider exterior building panels 28 for advantageously simulating multiple courses 26 of a classic surfacing material, for example such as clapboards, shingles, shakes or sla es. The panel 28 in FIG. 19 represents or simulates two courses 26 each of width "W", and the panel 28 in FI&. 20 represents four courses 26 each of width W. Between each of the courses 26 the face region 83 of the pa~el is inturned at 100 for simulatlng or representing a butt of the respective contiguous course above such inturn 100. The reinforcing ribbing 80 is shown including gussets 102 lntegral with the respective rib~ 82 and integral with the inturned butt region~ 100. The rearwardly facing portions of the ribs 8 immediately below the inturned butt region 100 (and al60 immediately below the upper margin 56 in all embodiments of panels 28 as shown) are flattened for providing flat rib surfaces facing toward and adapted to rest flush against a building structure 45 or 47.
In the illustrative two-course embodiment of the panel 28 shown in FIG. 19, the width "W" of each course 26 exposed to weather ~ay be in a preferred range from about 6 inches to about 14 inches, compared with six inches being the widest face board 3 ~ 7 in ~y experience simulated by a vlnyl extrusion, as was explain~d ln the BAC~GROUND. The width W of each course 26 may be in a more preferred range from about 7 inches to about 12 inches.
The overall panel width "W" in FIG. lS includes the width of the upper margin 56 as shown, which may have a width in a preferred range from about 1-3/4 inches to about 3-1/2 inches or in a more preferred range from about 2 inches to about 3 inches. Consequently, ~he overall panel width W' may be in a range from about fourteen inch~s to about thirty inches.
Selecting twenty-four inches as being a convenient illustrative overall building panel width W' for such a two-course exterior building panel 28, as shown in FIG. 19, and selecting 2-1/2 inches as being a convenient illustrative width for the upper margin 56, it is seen that each of the two courses 26 has an attractive exposed face width W of about 10-3/4 inches. This exposed face width of about 1~-3/4 inches advantageously lies near the ~iddle of ~he 10 to 12 inch board face width which is popular for home surfaces in Western regions of the U.S., as noted in the BACKGROUND.
For illustrative purposes, a 6tarter strip 54 is shown with the two-course~ panel 28 in FIG. 19. It is to be understood that the next higher two-course panel above the one shown in ~IG. 19 will not re~uire a starter strip, because its hook-flange 84, 86 will be engaged with and will be aligned on 2~63~

the building structllre 45 or 47 by the groove and lip 68, 66 on the upper margin 56 o~ the panel seen in FIG. 19. In other words, these two-course panels are installed on a building structure 45 or 47 using the same convenient advantageous "METHOD OP INSTALLING" previously described for the single-course panels 28.
With the illustrative embodiment of the ext~rior building panel 28 in FIG. 20, comprising four courses 26, there is shown a locking strip 104 in addition to the starter strip 54. This locking strip is secured to the building structure 45 or 47 by suitable fasteners 52. The four-course panel 28 includes an intermediate rearwardly projecting integral ledge strip 84 with a downturned hooking flange or lip 86 which may be produced as explained in connection with FIGS. 15-17. This ledge strip and downturned lip 84, 86 is located in an intermediate region of the panel 28, for example being on the rear of the second course 26 down from the upper maryin. This lip 86 is hooked behind the upwardly projecting lip 66 on the lockinq strip 104. This locking strip 104 may be identical with the starter strip 54. Each of them may include anti-over-drive ridges 71 and 72 as shown located above and below nail slots 70.
In the illustrative four-course embodiment of the exterior building panel 28, shown in FIG. 20, the width "W" of each course 26 exposed to weather may be in a preferred range from about 6 inches to about 14 inches. This width W of each 2~32~

course 26 may be in a more pr2~erred range from about 7 lnches to about 12 lnches. The overall panel width "W"' in FIG. 19, lncludes the width of the upper margin 55, as shown, which may have a width as discussed above regarding the two-course panel 28 shown in FIG. 19. Consequently, the overall panel width W' may be in a range from about twenty-four to about sixty inches.
Selecting forty-eight inches as being a convenient illustrative ovPrall building panel width W' for such a four-course exterior building panel as shown in FIG. 20, and selecting 2-1/2 inches as being a convenient illustrative width for th~ upper margin 56, it ~s seen that each of the four courses 26 has an attractive exposed face width of about 11-3/8 inches~ This exposed face width of about 11-3/8 inches advantageously lies near the middle of the 10 to 12 inch board face width popular for surfacing Western homes.
For illustrative purposes, a starter strip 54 is shown with the four-course panel 28 in FIG. 20. It is to be understood that the next higher four-course panel above the one shown in FIG. 20 will not require a starter strip, because its lower hook-flange 84, 86 will be engaged with and will be aligned on the building structure 45 or 47 by engaging the groove and lip 68, 66 on the upper margin of t~e panel shown in FIG. 19. The convenient, advantageous method of installing wider panels 28 wit~ a locking strip 104 as ~hown in FIG. ~0 will now be descsibed.

2~63~7 METHOD OF INST~LLING WIDER PANELS WI~H
I~rERMEDIATE LOCRING STRIPS __ _ The method of installing wider exterior building panels such as shown in FIG. 20 utilizing intermediate locking strips 104 is general.ly ~inilar to the method of installing single or multiple course p~nels 28 without locking strips, and proceeds as explained be.low.
During install~tion a starter strip S4 and a locking strip are both fastened along a lower portion of a wall structure 45 or a roo~ structure 47 where the respecti~e lower hooking flange 84, 86 and intermediate hooking flange 84, 86 are each to be engaged in hooked relationship on the building.
Snap-line horizontal chalk llnes or other suitable level markings on the wall or roof structure may be used to assure that both the s~arter strip 54 and locking strip 104 are level and are suitably spacd one above the other for receiving the lowermost ~initial) panel 28 in simultaneous hooking engagement with both attaching ~trips 54 and 104. By virtue of thi~
hooking engagement the lowermost (initial or first) panel 28 automatically become~ aligned on the building in the desired level position. Further, this hooking engagement advantageously supports the weight of the lowest multiple-course panel, thus freeing both of the in~taller's hands for accurately placing and ~663~

drlving fastener nalls 52 through the selQcted nailing slots 70 in the upper margin of this lowermost panel. No assistant nor temporary support is ne~ded for temporarily holding the lowermost panel level in its desired location while its upper margin is being fastened to the building.
A5 soon as fastening of the upper margin 56 of the lowermost panel has been accomplished by driving suitable fasteners 52, such as roofing nails, ~hen, another chalk line or suitable marking i~ put on the building structure 45 or 47 at the appropriate level at a predetermined spacing above the top edge 64 of the lowermost panel for location of the second locking strip 104. ~his second locking strip is fastened to the building structure 45 or 47 along this line or marking by suitable fasteners 52 driven into the building through nail slots 70 in the locking strip.
Next, the second multi-course panel 28 is applied to the building ~tructure by hooking engagement of the respective lower hooking flanga 84, 86 with the lip and groove 66, 68 of the already-attached lowermost panel and simultaneously by hooking engagement of the respective intermediate hooking flange 84, 86 with the already-fastened second locking strip 104, thereby automatically achleving an aligned level position for this second multi-course panel. Next, the upper ~argin 56 of this second ~ul~i-course panel is fastened ~o the building by suitable fasteners 52 driven into the building through the nail 2~3~7 slots 70 in the upper marg1n.
Then, a third locking strip is fastened to the building along an appropriately placed level chalk-line or o~her suitable level marking at a predetermined spacing above the top edge 64 of the now-secured second panel. Next, a third panel is hooked into engagement with this third locking strip and with the upper lip and groove 66, 6a of the now-secured second panel, thereby again automatically achieving an aligned level position for this third multi-course panel. Then, its upper margin i5 fastened to the building.
In this manner the installer proceeds upwardly along the building structure 45 ox 47 installing these mul~i-course panels employing the locking strips 104. An additional increment of time is involved in fastening the respective locking strips 104 to a building s~ructure for attaching a wide multi-course building panel 28, as shown in FIG. 20, employing such locking strips compared with the time involved for installing a narrower single-course or multi-course building panel 28, as shown in FIG. 4 or 19, wherein no locking strips are employed. This additional increment of time is compensated for by the fact that these wide multi-course panels provide a relatively large area of building coverage as each such panel .is installed on the building, and they have the advantage of providing relatively fewer horizontal joints between panels for a given area of building coverage.

It is understood that the exemplary molded exterior buildinq panel~ described herein and shown in the drawings represent only presently preferred embodiments of the invention.
Indeed, various modifications and additions may be made ko such embodiments without departing from the spirit and scope of the invention. For example, various reinforcing ribbing arrangements or other reinforcing may be provided. Various exterior building surfacing products other than clapboards, shingles, shakes and slates may be simulated and various arrangements of courses of 6uch other surfacing products may be simulated. Thus, these and other modifications and additions may be apparent to those skilled in the art and may be implemented to adapt ~he present invention for installakion on a variety of buildings and for use in a variety of climates and in different geographic regions without departing from the spirit and scope of the invsntion as claimed in the following claims.

Claims (39)

1. An exterior building panel made from thermoplastic material, said building panel comprising:
an upper margin, a lower margin, a main area between said upper and lower margins, said building panel having a front for facing to weather and a back for facing toward a building structure, said building panel having mounting means associated with said lower margin, said mounting means being engageable in fastening relationship with fastening means on an upper margin of a next adjacent lower building panel attached to the building structure for aligning said building panel with said next adjacent lower building panel and for fastening said lower margin to said upper margin of said next adjacent lower building panel with said lower margin in overlapping and covering relationship with said upper margin of said next adjacent lower building panel, said upper margin having a back side for placement against a building structure during attachment of said building panel to the building structure, Claim 1 -- cont'd said building panel having fastening means associated with said upper margin engageable in fastening relationship with mounting means associated with a lower margin of a next adjacent higher building panel for aligning said next adjacent higher building panel with said building panel and for fastening said lower margin of said next adjacent higher building panel to said upper margin with said lower margin of said next adjacent higher building panel in overlapping and covering relationship with said upper margin.

2. An exterior building panel as claimed in Claim 1, in which:
said mounting means associated with said lower margin comprise hooking means facing downwardly, and said fastening means associated with said upper margin comprise hooking means facing upwardly.

3. An exterior building panel as claimed in Claim 1, in which:
said hooking means facing downwardly are on the back of the building panel and are positioned at a juncture between said lower margin and said main area.

4. An exterior building panel as claimed in Claim 2, in which:
second mounting means are integrally formed on the back of said main area of the building panel and comprise hooking means facing downwardly.

5. An exterior building panel as claimed in Claim 1, in which:
said main area is shaped in at least one course, and each such course has a front face sloping forwardly and downwardly.

6. An exterior building panel as claimed in Claim 5, in which:
said main area is shaped in a plurality of courses, and each such course has a front face sloping forwardly and downwardly.

7. An exterior building panel as claimed in Claim 6, in which:
said main area in each of said courses has reinforcing ribbing integrally formed on the back.

8. An exterior building panel as claimed in Claim 7, in which:
front faces of said courses have widths "w" in a range from about 6 inches to about 14 inches.

9. An exterior building panel as claimed in Claim 7, in which:
said main area is inturned for shaping as a downwardly facing butt between each of said courses, and said reinforcing ribbing is integral with each such inturned downwardly facing butt.

10. An exterior building panel as claimed in Claim 9, in which:
said reinforcing ribbing has gussets integral with said inturned downwardly facing butts.

11. An exterior building panel as claimed in Claim 9, in which:
said reinforcing ribbing is flattened on the rear in areas immediately below each inturned downwardly facing butt, and such flattened areas are adapted for resting against a building structure on which the building panel is installed.

12. An exterior building panel as claimed in Claim 4, in which:
said main area is shaped in at least three courses, said second mounting means are integrally formed on the back of said main area in a predetermined one of said three courses, and said predetermined one course is a course immediately below another course immediately below said upper margin.

13. An exterior building panel as claimed in Claim 12, in which:
said building panel has a width in a range of about twenty-four to about sixty inches, and said main area in each of said courses has reinforcing ribbing integrally formed on the back.

14. An exterior building panel as claimed in Claim 1, wherein:
said upper margin has an upper edge with a row of mounting apertures spaced downwardly from said top edge, said row of mounting apertures extends horizontally along said upper margin, said apertures are horizontally elongated for accommodating thermal expansion and contraction of said exterior siding panel, a first ridge on the front of said upper margin is positioned above said row of mounting apertures and extends horizontally along said upper margin, a second ridge on the front of said upper margin is positioned below said row of mounting apertures and extends horizontally along said upper margin, said first and second ridges are positioned substantially symmetrically above and below said row of apertures, said first and second ridges are sufficiently far apart for receiving between them nail heads of fastener nails inserted through said apertures, said first and second ridges are sufficiently close together for preventing entry between them of a hammer head for preventing a nail head from being tightly driven against said Claim 14 -- cont'd upper margin for allowing thermal expansion and contraction of said exterior siding panel, and said hooking means associated with the lower margin and said lower margin are arranged for said lower margin to hide a first and second ridge, row of mounting apertures and fasteners inserted through said apertures of a next adjacent lower building panel installed on a building.

15. An exterior building panel as claimed in Claim 14, in which:
said ridges project forwardly about 1/16th of an inch relative to the region of said upper margin wherein said row of apertures is located.

16. An exterior building panel as claimed in Claim 1, in which:
said upper margin has a width in the range from about one and a half to about three inches, and said lower margin has a width sufficient in size for overlapping and hiding an upper margin of a next adjacent lower building panel installed on a building structure with said panel.

17. An exterior building panel as claimed in Claim 6, in which:
said lower margin has a front face continuing the forward and downward sloping of a front face portion of a lowest course in said building panel for simulating a building surfacing product selected from the group of building surfacing products comprising a clapboard course, a course of shingles, a course of shakes, and a course of slates, and said lower margin terminates at its bottom in a flange extending rearwardly for simulating a butt of such a siding product and for stiffening the bottom of said lower margin.

18. An exterior building panel as claimed in Claim 17, in which:
said main area and said lower margin are stiffened by reinforcing ribbing integrally formed on the back.

19. An exterior building panel as claimed in Claim 18, in which:
said mounting means comprise:
a horizontally extending and rearwardly projecting leg strip integral with said building panel, said leg strip projecting rearwardly beyond said reinforcing ribbing, Claim 12 --cont'd said hook means comprise a downturned lip on a rear portion of said leg strip spaced rearwardly from said reinforcing ribbing.

20. An exterior building panel as claimed in Claim 1, in which:
said mounting means comprise:
rearwardly projecting leg means integral with said building panel, and hook means including downwardly projecting lip means on a rear portion of said leg means.

21. An exterior building panel as claimed in Claim 20, in which:
said rearwardly projecting leg means and said downwardly projecting lip means extend substantially continuously along the back of said building panel.

22. An exterior building panel as claimed in Claim 18, in which:
said reinforcing ribbing comprises a multiplicity of ribs each having a triangular cross-sectional shape, and said ribs are integral with the building panel.

23. An exterior building panel as claimed in Claim 22, in which:
said reinforcing ribbing is arranged in a repetitive diamond pattern.

24. An exterior building panel as claimed in Claim 1, characterized further in that:
said building panel is molded from foamed thermoplastic material, and an entire face region of the building panel adapted for exposure to weather has a thickness "T" in a preferred range from about 5/32nds of an inch to about 3/8ths of an inch.

25. An exterior building panel as claimed in Claim 24, in which:
the foamed thermoplastic material of said building panel has a density in a preferred range of about 0.7 to about 0.4 of the density of the thermoplastic material prior to foaming for being comparable with densities of wood products.

26. A method of installing building panels on a building structure comprising the steps of:
providing at least one elongated starter strip having a back side and having an upwardly projecting lip positioned forwardly from said back side, fastening said starter strip to the building structure with said back side against the building structure and with said starter strip being in a predetermined position on the building structure, providing a plurality of building panels each having a front and a back with a fastening region extending longitudinally along an upper portion of each building panel, each building panel having an upwardly projecting lip positioned forwardly relative to its back, each building panel having hook means along a lower portion of the back, engaging the hook means of a first of said building panels onto said lip of said starter strip for holding the lower portion of the first building panel and for aligning said first building panel with said starter strip, fastening the fastening region of said first building panel to the building structure, Claim 26 -- cont'd engaging hook means of a second of said building panels onto the upwardly projecting lip of the first panel for holding the lower portion of the second building panel and for aligning said second building panel with said first building panel, fastening the fastening region of said second building panel to the building structure, engaging hook means of a third of said building panels onto the upwardly projecting lip of the second of said building panels for holding the lower portion of the third building panel and for aligning said third building panel with said second building panel, and fastening the fastening region of said third building panel to the building structure, and so forth.

27. A method of installing building panels on a building structure according to Claim 26, further characterized in that:
each of said building panels in said plurality of building panels has second hook means along an intermediate portion of the back in addition to said first hook means along a lower portion of the back, and Claim 27 -- cont'd further characterized by the steps of:
providing a plurality of elongated locking strips each having a back side and an upwardly projecting lip positioned forwardly from said back side, fastening a first of said locking strips to the building structure with its back side against the building structure and with said locking strip being uniformly spaced from said starter strip, said first locking strip being fastened to the building structure at a spacing from said starter strip suitable for enabling engagement of the first hook means of said first building panel with said starter strip and also for enabling engagement of the second hook means of said first building panel with said locking strip, engaging the second hook means of the first building panel with said locking strip in addition to the engagement of the first hook means with the starter strip, upon engagement of the first and second hook means, fastening the fastening region of the first building panel to the building structure, Claim 27 -- cont'd fastening a second of said locking strips to the building structure with the back side against the building structure and with said second locking strip being uniformly spaced from the first building panel, engaging the first hook means on a second of said building panels onto the lip of the first building panel, engaging the second hook means on the second building panel onto the lip of the second locking strip, upon engagement of the first and second hook means, fastening the fastening region of the second building panel to the building structure, fastening a third of said locking strips to the building structure with the back side against the building structure and with said third locking strip being uniformly spaced from the second building panel, and so forth.

28. A method according to Claim 26, including the further steps of:
making said starter strip of thermoplastic material and providing said starter strip with a longitudinally extending row of nail slots, Claim 28 -- cont'd each of said nail slots being longitudinally elongated, said nail slots being longitudinally spaced from each other in said row, providing on a front of said starter strip a pair of anti-over-drive ridges respectively above and below said row of nail slots, said pair of ridges being sufficiently widely spaced for receiving a nail head between them, and said pair of ridges being sufficiently closely spaced for preventing entry of a hammer head between them for permitting thermal expansion and contraction of a starter strip after fastening to the building structure by headed nails driven through said slots.

29. A method according to Claim 27, including the further steps of:
making said starter strip and said locking strips of thermoplastic material and providing said starter strip and each of said locking strips with a longitudinally extending row of nail slots, each of said nail slots being longitudinally elongated, said nail slots being longitudinally spaced from each other in said row, Claim 29 -- cont'd providing on a front of said starter strip and on a front of each of said locking strips a pair of anti-over-drive ridges, respectively above and below the row of nail slots, said pair of ridges being sufficiently widely spaced for receiving a nail head between them, and said pair of ridges being sufficiently closely spaced for preventing entry of a hammer head between them for permitting thermal expansion and contraction of the starter strip and locking strips after fastening to the building by headed nails driven through nail slots.

30. The method of making an exterior building panel from thermoplastic material comprising the steps of:
forming the building panel to have an upper margin with horizontally elongated nail slots therein for accommodating thermal expansion and contraction of the panel and with a back of the upper margin adapted to rest against a building structure when the upper margin is fastened to the building structure and with an upwardly projecting lip spaced forwardly relative to the back for defining a groove behind said lip when the upper margin has been nailed to the building structure and with a rearwardly projecting ledge strip extending horizontally along a rear lower portion of the panel, Claim 30 - cont'd heating said ledge strip for softening it, bending a rear edge portion of the heated softened ledge strip down for forming a depending lip on said ledge strip, and cooling the ledge strip for setting said depending lip for forming a hook-like member extending horizontally along a rear lower portion of the panel adapted for hooking engagement into a groove and onto an upwardly projecting lip of a next lower panel already fastened to the building structure.

31. A method of making an exterior building panel according to Claim 30, including the steps of:
routing a rear lap-joint channel extending vertically along near an end of the panel with a rearwardly projecting lip extending vertically along said end adjacent to said rear channel, and routing a front lap-joint channel extending vertically along near the other end of the pan 1 with a forwardly projecting lip extending vertically along said other end adjacent to said front channel.

32. A method of making an exterior building panel according to Claim 30, including the further steps of:
forming the building panel with a second rearwardly projecting ledge strip extending horizontally along a rear intermediate portion of the panel, heating said second ledge strip for softening it, bendinq a rear portion of the heated softened second ledge strip down for forming a depending lip on said second ledge strip, and cooling the ledge strip for setting said depending lip for forming a second hook-like member extending horizontally along a rear intermediate portion of the panel adapted for hooking engagement into a groove and onto a portion of a locking strip fastened to the building structure.

33. An exterior building panel molded from thermoplastic material, said exterior building panel comprising:
an upper margin, a lower margin and a main area extending between said upper and lower margins, said building panel having a front for facing to weather and a back, said upper margin having a back side for placing against a building structure during attachment of the upper margin to the building structure by fasteners engaging the upper margin, Claim 33 -- cont'd said upper margin being adapted for overlapping by a lower margin of a next adjacent higher one of said building panels fastened to the buildlng structure, sa.id upper margin having a top edge, said top edge being positioned forwardly from said back side for spacing said top edge away from a building structure to which the upper margin is fastened, said building panel having hook means on the back of said lower margin, said hook means being for hooking engagement on the top edge of a next adjacent lower one of said building panels fastaned to the building structure for supporting the panel and for aligning the panel with said lower siding panel, and said hook means in such hooking engagement serving for holding said lower margin in an installed position with said lower margin overlying an upper margin of said next adjacent lower building panel.

34. An exterior building panel according to Claim 33, wherein:
said upper margin has a row of mounting apertures spaced downwardly from said top edge, Claim 34 -- cont'd said row of mounting apertures extend horizontally along said upper margin, said apertures are horizontally elongated for accommodating thermal expansion and contraction of said building panel, a first ridge on the front of said upper margin is positioned above said row of apertures and extends horizontally along said upper margin, a second ridge on the front of said upper margin is positioned below said row of mounting apertures and extends horizontally along said upper margin, said first and second ridges are positioned substantially symmetrically above and below said row of apertures, said first and second ridges are sufficiently far apart for receiving between them nail heads of nails inserted through said apertures, said first and second ridges are sufficiently close together for preventing entry between them of a hammer head for preventing a nail head from being tightly driven against said upper margin for allowing thermal expansion and contraction of said building panel, and Claim 34 -- cont'd said hook means and lower margin are arranged for overlying a first and second ridge, row of mounting apertures and nails inserted through said apertures of a next lower building panel fastened to the building structure.

35. An exterior building panel according to Claim 34, in which:
said top edge projects upwardly from said first ridge.

36. An exterior building panel according to Claim 33, in which:
said hook means comprise a horizontally extending rearwardly projecting strip of thermoplastic material having a downturned rear edge for hooking upon a top edge of a next adjacent lower panel, said building panel has an inturned flange on a bottom edge of said building panel, and said inturned flange is spaced downwardly from said hook means.

37. An exterior building panel according to Claim 35, in which:
said hook means comprise a horizontally extending rearwardly projecting strip of thermoplastic material having a downturned rear edge for hooking upon a top edge of a next adjacent lower panel, said building panel has an inturned flange on a bottom edge of said building panel, and said inturned flange is spaced downwardly from said hook means.

38. An exterior building panel as claimed in Claim 2, in which:
said hooking means facing downwardly includes a ledge extending horizontally on the rear of the building panel, said ledge has a downwardly projecting lip on a rear portion of the ledge, said downwardly projecting lip has a front surface sloping downwardly and rearwardly, said hooking means facing upwardly includes an upwardly projecting lip, and Claim 38 -- cont'd said upwardly projecting lip has a rear surface sloping downwardly and rearwardly for engaging a downwardly and rearwardly sloping surface of a downwardly projecting lip on a next adjacent higher building panel for wedging the downwardly projecting lip on said next adjacent higher panel toward a building structure on which the building panel and said next adjacent higher building panel are both installed.

39. An exterior building panel as claimed in Claim 33, in which:
said hook means on the back of said lower margin include a rearwardly projecting ledge and a downwardly projecting lip on a rear portion of said ledge, said downwardly projecting lip has a front face sloping downwardly and rearwardly, said top edge has a rear face sloping downwardly and rearwardly for engaging a downwardly and rearwardly sloping face of a downwardly projecting lip on a next adjacent higher building panel for wedging the downwardly projecting lip on said next adjacent higher building panel toward a building structure on which the building panel and said next adjacent higher panel are both installed.