US2226248A - Building construction - Google Patents

Description

Dec. 24, 1940. E. H. LUNKEN BUILDING CONSTRUCTION Filed Jan. 18, 1938 4 Sheets-Sheet 1 1 N VENTOR.

ATTORNEY.

Dec. 24, 1940. E. H. LUNKEN BUILDING CONSTRUCTION Filed Jan. 18, 1938 Q 4 Sheets-Sheet 2 INVENTOR. 5 dz ufld 361,130 unite ATTORNEY.

Dec. 24, 1940. LUNKEN 2,226,248

BUILDING CONSTRUCTION Filed Jan. 18, 1958 4 Sheets-Sheet s A, 4 f ll 5 pwsal-i 1 INVENT OR. dmund 1C Jbunlten BY Z 2 i ATTORNEY.

Dec. 24, 1940. E U'NKEN 2,226,248

BUILDING CONSTRUCTIDN Filed Jan. 18, 1938- 4 Sheets-Sheet 4 EXTERIOR 55 INTERIOR 215 5 12 54 82 INVENTOQ-R.

Gdm'ufld J1: fiunfien ATTORNEY.

Patented Dec. 24, 1940 UNITED STATES PATENT OFFICE BUILDING CONSTRUCTION Edmund H. Lunken, Hartsdale. N. Y. Application January 18, 1938, Serial No. 185,489

5Claims. (Cl. 189-34) This invention relates to building construction and particularly to slabs, sheets or blocks for forming the wall of a building.

It is an object of this invention to provides.

5 wall slab or sheet so constructed and formed as to be particularly useful in connection with the clamping means set forth and described in my Patent No. 2,053,438, issued on September 8, 1936, and titled Building construction.

1 Heretofore, it has been found that any metallic frame-work for a building, including clamping combinations described in said patent, constitutes a heat conductive element which tends to equalize the temperature of the exterior and interior 15 surfaces of the wall whichis supported by such frame. When the outside temperature is lower than that of the interior of the building, the

'inner portion of the steel frame-work is cooled by conductivity of the metal which provides a :0 ready means for the escape of heat. This not only leads to an unnecessary and uneconomical cooling of the interior of the building, but also results in condensation of moisture from the air in the interior of the building upon and adjacent 25 to the inner portion of said frame. Wherever there is a system which replenishes the moisture in the air for the purpose of maintaining humidity at a predetermined standard, this condensing efi'ect even results in pools of water which :0 collect on the floor of the room near the steel members. Where there is no such moisture replenishing system, then the air in the room, if it is not cooled, will become dry. Added to the difficulty which thus arises is the fact that the 35 expense of heating the interior of the building is necessarily increased when heat is steadily conducted away. It is sometimes found desirable however to face the surfaces of the wall slabs, which are supported by the frame, with metal.

40 Such a slab, of course, will produce all of the objectionable results heretofore noted in regard to the metallic building frame alone. Even if the outer and inner surfaces of such wall slab are insulated from each other in the slab itself,

and/ or interior surfaces with metal, such surfaces not being conductively connected to each other and thus preventing the rapid passage of heat from one wall surface to the other. Other ohjects are to provide a wall slab for use in connection with the clamping device heretofore mentioned which will tend to prevent the conduction of heat from the inner to the outer surface of the wall through the metallic building frame and clamping device. Other objects are to provide 5 an exterior and/or interior metal faced wall construction for a building wherein no path is provided for the ready conduction of heat from one surface to the other of said wall.

Further objects and uses of this invention wfll be apparent from the following description and drawings in which:

'Figure 1 is a sectional view in perspective of a plurality of my improved wall slabs held in place by the clamping means set forth in my Patent No; 2,053,438, issued September 8, 1936. Figure 2 is a sectional horizontal plan view showing a modified form of my improved wall slab.

Figure 3 is a view in perspective of the nonconductive frame for my improved wall slab.

Figure 4 is a fragmentary view in perspective showing in detail the manner in which one wall slab is mounted upon the other.

Figure 5 is a fragmentary view in perspective showing a corner of my improved wall slab.

Figure 6 is a top plan view of an improved form of clamping member. Figure 7 is a side elevation of clamping members slidably connected through a coupling.

Figure 8 is a sectional elevation on the line 8-8 of Figure "I looking in the direction of the arrows. I

Figure 9 is a detail view of the metallic surface of the wall slab showing a means for compensat- 5 ing for expansion.

Figure 10 illustrates a modified means for mounting my improved wall sla-b.

Figure 11 shows a modified form of the mounting means shown in Figure 10.

Figure 12 illustrates in sectional horizontal plan view the formation of an outside corner between walls formed from my improved wall slab.

Figure 13 illustrates in sectional horizontal plan view the formation of an inside" corner between walls formed from my improved wall slab.

Figure 14 illustrates in sectional horizontal plan view a modified form of the construction shown in Figure 2. v

Figure 15 illustratesv in horizontal section clamping members having it treated bearing surface.

modified forms of elements 52 and 55 of Figure 10. Referring now to Figure 1, the wall slabs I a held against the T shaped frame-work 2 of the structure by the clamping member 3 as described in the patent before mentioned;

The inner surface 4 of the wall slab is fastened by any suitable means as by the nails 8 to a frame 8. In the event that the said frame 6 is made of wood, nails would be the most suitable fastening means; butrivets, grommets or other means may be used for fastening depending upon the type of material used for the frame, which should, however, in all cases be made of material which is a poor conductor of heat. The inner surface 4 may consist of any material which is suitable for an interior wall and which may be fastened to a frame, but preferably consists of a thin metallic sheet. The outer wall I may consist of the same type of material as the inner surface and is also fastened to the frame 6 in a suitable manner as by the nails 5'.

It will be noted that the outer and inner surfaces of the wall slab are not directly connected to each other but are attached to the frame 6 only. Such frame 6 is formed from a material which is a p or conductor of heat, such as wood, and thus prevents the communication or conduction of heat from one wall surface to the other. To strengthen the wall slab and to render it more efiicient as a heat insulating member, the space 8 between the outer and inner surfaces of the wall may be filled with various insulating and/or strengthening substances such as cement mixtures containing expanded mica, granular materials or insulating granules. Flanges 9. 9 may be attached by welding or other means to the metallic surfaces 1 and 4 of the wall slab to assist in anchoring such surfaces to the filler material occupying space 8, thus tending to produce a solid, united and rigidified unit. In order to lighten the wall structure as well as to increase its insulating qualities, dead air spaces l0, l0 may be created in the substance which fills the space 8; preferably, such spaces are created by theinsertion of a paper tube in the space 8 before such space is filled with strengthening material. The frame 6 is provided with a groove ll adapted to receive the arm l2 of the T shaped beam 2. Various means may be used to mount the slab upon the T beam by means of the groove. Thus the groove on one edge of the wall slab may be fitted upon the T beam and then a T beam may be mounted in the groove at 65 the opposite edge of the slab and secured to a proper base. Or the wall slab may be raised to the top of the T shaped beams, the grooves H placed upon the arms l2, and the wall slab then slid down into position upon the beam. This 0 mounting of the wall slab upon the T beam may be used alone to hold the wall slab in position provided said slab is given a secure base upon which to rest. However, the use of the clamping member 3 (as set forth in my patent aforemen- 65 tioned) will serve to secure the wall in place and serve as a mechanical lock, caulking device, and expansion joint.

In order to reduce conduction of heat by means of the exposed portion l3 of the T beam, a rabbet which heat may be conducted from one surface to the other of the wall slab. In addition, the space between the exposed portion I! of the T beam and the batten I! may also be used to lead cables or pipes for wiring or other purposes. 5

The outer wall surface may be indented adjacent the vertical edges in order to receive the head ll of the clamping member 3. Such indentations l9, I! serve not merely to produce an ornamental appearance and a flush batten it, but 10 also to reduce to a minimum the thickness of the lap joints which the batten must cross, as hereinafter explained particularly in connection with Figure 4.

To assist in weather-proofing the structure, the 15 base of the outer wall surface on each slab has an extension 22 adapted to lie in an indentation 23 along the top of the subjacent wall slab, thus closing any opening through which air may enter and forming a flashing for water stopping. The 90 manner in which such extension 22 fits into such indentation 23 and closes the gap is more clearly seen in Figure 4. It will also be seen that the manner of attachment of the metallic wall surfaces to the frame 6 at the place where two wall as slabs are placed one upon the other as shown at 20 (Fig. l) is such as again to prevent any conductive connection between the outer and inner metallic wall surfaces.

Figure 3 illustrates the particular conformation 30 of the frame 8 best adapted to produce the results hereinbeiore described, in which it is apparent that the groove II and the rabbet l8 extend the entire length of the vertical portion of said frame; and that the base of said frame (seen at 35 20 of Fig. 1) is merely a solid member of poor thermal conductivity to which the outer and inner wall surfaces may be attached.

In Figure 4, I have illustrated in fragmentary perspective the detail of the wall slabs at a corner 40 showing the manner in which one slab rests upon the other. The extension 22 on wall slab l' rests in the-horizontal indentation 23 of wall slab I. Each wall slab will have such an extension at its base and a corresponding indentation at its upper 45 horizontal edge. The vertical indentation I8 of wall slab I registers with the vertical indentation I! of wall slab I, the extension 24 at that point consisting of a single thickness of metal or other material so that the horizontal opening between 50 the two walls is closed ofl, and, at the same time, the vertical clamping member 3 (Fig. 1) will not be distorted or its clamping pressure weakened by too great a variation in the surface of the indentation l9, 19 in which it is to rest.

Figure 5 clarifies in fragmentary perspective the corner detail of the wall slab structure and shows more clearly thev base thereof. Here is illustrated in greater detail the manner in which the surfaces 1 and 4 are attached to.the frame 6 by the nails 5' and 5 respectively, and there is also shown the relationship between the frame 8, including rabbet It and groove II, and the two wall surfaces. It should be noted that, while surface 4 is preferred for the interior of said wall 55 slab, such surface may be used as the exterior surface where a particular form of construction or purpose may render such use feasible.

It is here intended to illustrate merely the most desirable embodiment of my invention. It will be obvious that the vertical portions of the frame 8 may have many conformations for receiving and resting against the head ii of the T beam 2, and the batten i! may rest directly against the T beam ,or against the inner wall surface: or that the inner walls themselves may be formed so as to meet and present a plane surface at such meeting line and thus enclose the T beam.

In Figure 2, I have disclosed one such modified form of wall slab in which the outer wall surface I01 and the inner wall surface I04 are attached by nails I and I05 respectively to a frame I00 which in turn has a rabbet III which may be placed against the head II3 of the T beam I02. A clamping member I 03 may then be mounted on the pins and hold the wall slab in place as described in my patent aforementioned. And the batten III may then be mounted on the interior surface to complete the plane surface and cut off conductive connection through the head H3. The batten I" may be placed directly against the head H3 or it may be so mounted as to leave a hollow space between the head H3 and the batten III for purposes hereinbefore described. This construction of the wall slab makes it possible to insert the slab after the entire frame of the building has been erected, and also makes possible the replacement of individual slabs without disturbing other slabs. To facilitate the erection of the wall structure by the use of slabs of this modified form, the slab may be laid against the T beam head II3 so that the rabbet III rests against it and nails I26, pins or other suitable fastening means (depending on the material of which frame I06 is made) may be partially driven into the frame I06 so that their heads will rest against the head of the T beam H3 and thus hold the wall slabs temporarily in place until the clamping member I03 may be applied. After the clamping member I03 is applied and holds the wall slabs in place, the nails I26 may be withdrawn, or completely driven in, as shown in Fig. 2, or may be left in partially driven in position thereby providing additional security for the slabs in the event that the batten II! is not intended to rest directly against the head I I3. Such nails, if not;driven in, may be used, if desired, to provide a bearing against which the batten II'I may rest.

It will thus be seen that, withrthe wall slab constructions herein disclosed, there is no heat conductive metallic path or connection between the outer and inner surfaces of the wall formed from such slabs; the wall itself may be a heat insulating member; weather proofing is achieved along the vertical seams by the seating of the T beam head in the grooves II or against the rabbets III (Fig. 2) and the placing of the batten II or III; the clamp 3 or I03 completes such vertical joint, forms an expansion joint and further assists in such weather proofing; weather proofing is also obtained along the horizontal seams by the overlapping extension 22; caulking is no longer necessary, and any plastic connectionor adhesive binding between the wall constituents is rendered superfluous. The size of the wall slab is limited only by the size and conformation of the building and the means available for handling the slabs. Construction of the building is thus facilitated and the finished result is a rigid interconnected, heat insulating, weather-proof wall of low thermal conductivity.

It should be noted that any problem relating to expansion due to temperature changes of the metallic wall surfaces is minimized by the thinness of such metallic surfaces. Instead of distorting the wall slab, the surfaces 4 and I (Fig. 1) will, by reason of their light gauge, tend to wrinkle under expansion by heat, and the elasticity of the metal will compensate for contrac-,

tion due to a lower temperature. The anchors or flanges 3 welded on the interior of the metallic surfaces (Fig. 1) cause the surfaces to adhere to the wall slab and confine any distortion of any portion of the surface-to that portion only. Any possibility of the steel separating from its backing may further be obviated by providing means to absorb the expansion of the surfaces as shown in Figure 9. The wall surface 201 which is bound tothe material fllling the space 203 by the flanges or anchors 203 may be creased at 2"), each crease lying between two rows of anchors 203. Such crease may be relatively shallow and may have various forms as expediency requires but it will serve to take up any expansion or contraction of the metallic wall surfaces so that the remainder of x the wall will be undistorted. I have found that this type of crease or wrinkle for the purpose of providing a predetermined area at which distortion of the wall surface may be taken up also prevents possible crackingv or flaking of the finish on the wall surface. The crease or wrinkle in various forms, may, of course, be applied in vertical lines or in horizontal lines or both as width and construction of the wall slab and other considerations require, and may be applied to either the outer metallic surface, the inner surface or both.

Owing to the fact that the positioning of the head of the T beam in the groove II (Fig. 1) of the wall slab serves to hold the slab in place upon the beam, the clamping member 3 is required only to secure a mechanical seal that permits expansion and contraction of the slab in a horizontal direction. 01' course, in the type of construction shown in Figure 2, the clamping member I03 serves not merely as a mechanical seal but also as a member which holds the wall lin place. 'These results may be achieved by a extremities of the head 3| of the clamp, said head being a straight non-angular member. With the head of the clamp thus arranged, the outer surface of the wall thus formed will be flat and uniform as seen at I 03 of Figure 2, and will not present any undesired extrusions, breaks or lines. A driving down of this form of clamp in the manner described in my Patent No. 2,053,- 438 will cause a slight distortion of portion 33 (Fig. 6) of the head of the clamp and the elasticity of the metal of which the clamp is formed will serve to hold the bearing surfaces 30 against the wall slabs under all conditions. since there is no bend line in the head (such as that shown at I3 of Figure l) aboutwhich the arms may be permanently bent, the effectiveness of the clamp is increased.

In addition,

Where, for the sake of convenience, it is desired to use short lengths of clamping members to facilitate the attachment of the basal row of wall slabs to the T 'beams without reference to the upper rowof slabs, or where it is desired to lock one wall slab in place before placing the superjacent slab upon it, gaps may appear between the superposed clamping members. Such gaps, apart from being unsightly, may tend to destroy the weather proof qualities of the completed wall. It may also be necessary to provide for gaps between superjacent clamps so that the clamps will be in short lengths only, for the purpose of preventing expansion over a long length of clamp from loosening the hold of such clamps. In such cases, a sliding coupling 35 may be placed between such clamps (Figs. 7 and 8) with flanges 35 enclosing the head I8 of the clamps 3, such coupling being a tight fit, but the heads of the clamps being slidable within the flanges. Such coupling will permit independent expansion, contraction and adjustment of each length-of clamp, and will at the same time present a continuous unbroken exposed surface.

It may, under specific conditions, be desirable that the frame of the building consist of beams which are. not necessarily limited to the T beam construction hereinbefore described. Various modifications may then be made in accordance with the type of frame structure desired, which will nevertheless give the necessary support and the proper mounting for the wall slabs. Thus, in Figures 10 and 11 I have illustrated two types of construction of an H beam frame for mounting the wall slabs. In Figure 10, the vertical frame work consists of two channel members 50 and5I erected together to form an H beam with a metallic or non-metallic plate 52 between them and extending outwardly therefrom and being held in place between the channel members by welding, riveting, bolting or other suitable means. The plate 52 and the flanges 53 and 54 of the channel members together form in effect the T beam previously described. The plate 52 will also carry the pins 55 to assist in mounting the clamping member as described in my patent aforementioned. The wall slab I will then be mounted on the frame in the manner previously described, the grooves II fitting over the arms 53 and 54. A wall slab of the type shown in Figure 2 may also be used in connection with this type of frame, the rabbets III lying against the arms 53 and 54.

In the event that such plate 52 is made of sheet material as is plate I52 of Figure 16, then, instead of pins 55 (Fig. 10),wings I55 (Fig. 16) punched from said plate may be provided at suitable intervals to mount the clamping member I03 (Fig. 16) Such wings will necessarily be cut or punched and bent in such a manner as to permit the notches I55 on the legs of the clamping member I03 to be driven down on such wings without distortion.

In Figure 11, I have shown a modified form the H beam construction for the vertical framev work in which the H beam 56 having arms 51 and 58 has welded thereto or otherwise mounted thereon in any suitable manner a T beam 59 having pins 50. The post 59 and the arms 50 and 51 will form the T beam construction required to support the wall slab as previously described in connection with Figure 10.

The inner flanges 5| and 62 of the channels 55 and 5I (Fig. or, if the construction shown in Figure 11 is used, then the inner arms 83 and 54 of the H beam 55, will be covered and concealed by the non-conductive moulding 64 shown in Figure 10 which will fit over such flanges and abut against the inner surface 4 of the wall effectively closing any conductive metallic connection between the outer and inner wall surfaces.

The type of wall slab hereinbefore described, and the erection thereof on a T beam frame work or on a modified form of frame work as above set forth, lends itself readily to the formation of corners in the wall of a house. Figures 12 and 13 illustrate generally the type of construction for an outside" corner and an inside corner respectively. In Figure 12, the "outside corner, the T beams are erected so that the heads thereof I3 lie toward the interior of the wall to be formed: the wall slabs I are mounted on the T beams in a manner which is now understood; an outer post I0 having rabbets II is laid into the outer side of the corner so that the rabbets II rest against the arms I2 of the T beams; the post I0 has an outermetallic surface I2 fastened to the post by the nails 13 and having indentations I4 to receive the clamping members I5 which are to be mounted on the pins I3. To complete the corner, a finishing piece I1 is inserted at the interior of the corner; this finishing piece has extensions I3 which lie against the rabbets II of the wall slabs I and it is held in place by the series of screws I5 driven from its inner surface through into the post I0. Here again it will be seen that the post I0 and the finishing piece 11 being low-conductive of heat, there is still no metallic heat conductive connection between the outer and inner wall surfaces. The inner .surface of the finishing piece TI may also be metal faced if desired. Only preferred forms of the post and finishing pieces have been given; it will be understood that many other forms and means of attachment thereof may now be used within the spirit of my invention. Thus the post I0 and the finishing piece I! may be a single member with a groove to fit over the arms of the T beam and a batten to close up the interior gap.

Such a groove type of construction is shown in Figure 13 where the formation of an inside" corner is shown. The T beams are so erected that their heads I3 lie away from the angle to be formed; toward the interior of the wall to be formed. The wall slabs Iare mounted on the T beams 2 in a. manner which is now understood, and a corner piece 30 having grooves Oi is mounted at the corner by fitting such grooves upon the corresponding arms I2 of the T beam head I3. This corner piece 30 is of low-conductive material, has an interior metallic surface 82 and an exterior metallic surface 33 fastened thereto by any suitable means. It also has a rabbet 84 at each side, corresponding to the rabbet I5 of the wall slabs I against which the batten Il may rest. And it also has indentations corresponding to the indentations I3 of the wall slabs for the purpose of receiving the heads of the clamping members I5. Here again,

it will be seen that, the corner'piece or post 33 being of low-conductive material, there is no metallic heat conductive path between the outer and inner wall surfaces.

Many other types of construction are possible.

Thus, in Figure 14, I have illustrated a modified manner of using the wall slab construction shown in Figure 2, wherein the same type of wall slab is mounted against the same type of T beam. The wall slabs may however be held in place temporarily by laying wood or other low heat conductive strips 90 in the angle formed by the frame I06 of the wall slabs and the head II3 of the T beam and driving nails I25 pins or other suitable fastenings through such wood strips 90 and into the frame I06. These strips 00 will then bear against the head II3 of the T beam member I02 and hold the wall slabs in place until a clamping member can be placed upon the pins I25. To complete the inner structure or surface a batten 9| may be mounted against the head II3 of the T beam and the wood strips 00. Such batten may be fiat and thus rest only against the strips 90 creating a hollow space between it and the head II3 of the T beam or it may have the form shown in Figure 14.

In the foregoing special modifications, I have such walls have been shown for the purpose of explaining my invention, and that such structures may take many forms not herein illustrated and described but all falling within the limitations of the foregoing description. Such walls will be weather-proof, low-conductive of heat, sturdy, inexpensive in construction and easy to erect, with ample provision for expansion and contraction due to temperature changes.

Also, with the type of wall slabs shown in Figures 2 and 14 it will be possible to replace individual wall slabs without interfering at all with superposed or subjacent wallslabs; and, with any of the wall slabs herein described, it will be possible to replace individual wall slabs without moving or interfering with laterally adjacent wall slabs. It is even possible to mount a window or a door in a frame of the type shown in Figure 3 or in a frame of the type shown by I06 of Figure 2, and to move such window from one place to another of the wall as desired, by exchanging a slab containing a window or a door with one which does not.

In all cases, a weather-proof low-conductive seal may be obtained between the wall slabs. And to assist in obtaining such a weather-proof seal. the bearing surfaces of the binding clamps 3, 3!, I03, 15, may be faced with a sealing substance 95 (Fig. 15) such as tar paper, felt, asphalt .impregnated tape, or other substances which will create such a seal. Such a seal is an added precaution only, and, for reasons which have already been set forth, may well be unnecessary. Having described my invention, I claim:

1. In combination, a vertical metallic frame for a building consisting of vertical members having lateral projections; a non-metallic batten; wall slabs; each slab having a peripheral frame of material having low thermal conductivity, vertical metallic surfaces fastened to said peripheral frame, and means on said peripheral frame whereby said slab may be mounted on the lateral projections of the vertical members of-said building frame; said slabs being mounted laterally adjacent to each other with a vertical member of the building frame between adjoining slabs; clamping means positioned exteriorly of said slabs upon the vertical members of said building frame and pressing said slabs against the lateralproiections from said vertical frame members; said batten being mounted interiorly of said wall slabs in the vertical gap between them; there being no metallic heat conductive path from one surfac to the other of the wall. i

2. A framework for a wall of a building structure, each vertical member of said framework comprising two members of U shaped section fastened together; the flanges of said U shaped members lying in a plane parallel to the wall; a

plate continuous with and fastened between said members and extending outwardly therefrom toward the exterior of said wall; the flanges of said members lying toward the exterior of the wall and said plate forming together a T sectioned member; means on said plate engaging a clamping member.

3. A framework for a wall of a building structure, each vertical member of said framework comprising two members of U shaped section fastened together; the flanges of said U shaped members lying in a plane parallel to the wall; a plate continuous with and fastened betweemsaid members and extending outwardly therefrom toward the exterior of said wall; the flanges of said members lying toward the exterior of the wall and said plate forming together a T sectioned member; means on said plate engaging a clamping member; said means comprising wings bent out from said plate and extendingin a plane angularly thereto.

4. A slab for use in forming the wall of a building, said building having a vertical metallic frame consisting of vertical members having lateral projections, said slabs having a peripheral frame of material having low thermal conductivity and vertical metallic surfaces fastened to said peripheral frame, said peripheral frame having a recess along each vertical edge thereof each recess being so formed as to receive a lateral projection of a vertical member of said building fram and to cooperate in holding the slab in vertical position upon said frame; a recess in the outer surface along each vertical edge of the slab adapted to receive the head of a clamping member; and an indentation along the upper horizontaledge of the outer surface of said slab, and a corresponding extension along the lower horizontal edge of the outer surface of said slab; there being no metallic heat conductive path from one surface to the other of said wall when said slab is mounted on said building frame.

5. A slab for use in forming the wall of a building, said building having a vertical metallic frame consisting of vertical members having lateral projections, said slabs having a peripheral'frame of material having low thermal conductivity and vertical metallic surfaces fastened to said peripheral frame, said peripheral frame having a recess along each vertical edge thereof, each recess being so formed as to receive a lateral projection of a vertical member of said building frame and to cooperate in holding the slab in vertical position upon said frame; a recess in the outer surface along each vertical edge of the slab adapted to receive the head of a clamping member; and an indentation along the upper horizontal edge of the outer surface of said slab, and a corresponding extension along the lower horizontal edge of the outer surface of said slab; and a thin metallic extension along the bottom edge of said vertical recess in the outer surface for providing a thin lapv joint with a subjacent slab along said recess; there being no metallic heat conductive path from one surface to the other of said wall when said slab is mounted on said building frame.

EDMUND H. LUNKEN.

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