US2192458A - Roof construction - Google Patents

Description

f March G. E. SWENSON Er AL v ROOF CONSTRUCTION Filed Dec. 24. 1937 2 Sheets-sheaf; 1

I v Geomejfimenaay ,i'iizzlefiederrmk J71 G. E. SWENSQN ETI' AL ROOF CONSTRUCTION March 5, 1940.

2 sheets-skeet 2 Filed Dec. 24. 1937 Patented Mar. 5, I

UNHTED STATES PATENT oFFicE ROOF CQNSTRUC'IION George E.-Swenson, Hastings on Hudson, N. Y.,

and Emile Frederick, In, New Orleans, La., assignors to The Celotex Corporation, Chicago, 111., a corporation of Delaware Application December'24, 1937, Serial No. 181,474

19 Claimsv (Ol.1086) In the construction of roofs for various struc-' or pitch, or the like, in which the insulation sheets tures, it has in the past been extremely diflicult are bedded. There is applied over the insulation to provide a roof structure which includes thersheets saturated and coated felt roofing or the mal insulation positioned particularly on the top like, which is mopped down to the upper surface surface of the roof structure which functions of the insulation board with asphalt, pitch, 5 satisfactorily. There are various reasons for the or the like, which felt roofing when properly ap-. unsatisfactory results obtained with the various plied comprises a water and substantially air imsuch constructions that have heretofore been pervious top cover for the entire construction.

used among which defects probably the principal Thermal insulation is ordinarily obtained by In item has been that'roofing surfaces laid over the use of materials which are relatively light-l0 such insulated roof constructions have a decided and porous or cellular so that an appreciable tendency to blister, that is, for the roofing to portion thereof comprises cells, channels, or the. loosen in spots and be raised as a distinct blister like, which are normally more or less closed air and in fact over various of such roof structures chambers in which the enclosed air is in fact the is such blistering has at times been of sufflcient insulating medium. Still air, that is, air which 16 extent that substantially the entire roof covering is not free to freely circulate: is one of the best has been loosened from the underlying portions thermal insulators known and its properties are of the structure. availed of in manufacturing thermal insulating The difliculties encountered have been particmaterials as above pointed out. 20 ularly severe where such constructions have in- The factthat thermal insulating materials con- 20 volved concrete roof decks although such diflitain a relatively large amount of air is detriculties are from time to time met in substanmental in the construction of a roof structure tially all types of roof construction which involve comprising the various elements as above pointthe useof an insulating material having laid ed out in that this air contained in the insulatthereover saturated and coated roofing felts. ing material expands very considerably when the 25 The loosening of the roof surfacing sheet in roof structure is heated as in the summer time, such roof structures appears to be due to the and this creates a definite pressure within the fact that the roofing sheet is laid on the thermal structure between the air impervious roofdeck insulating material adhered thereto with as-' and the air impervious roofing felt covering.

- phalt, pitch, or like binding substance, which sub- Such air pressure developed within the structure 30 stances at temperatures around, say, 120 degrees is sufllcient to break the bond of the asphalt, or Fahrenheit, which are commonly encountered on like adhesive, by means of which the roofing felt roofs in the summer time, soften and have no is adhered to the surface of the insulating masubstantial internal strength so that a relatively terial and-it results that the roofing felt is raised,

"5 slight force tending to part the roof sheet from at leastin places, from the insulating material the insulating sheet will readily cause separation and the so-called blisters are formed. In addidue to such softened condition of the adhesive. tion to the pressure created by the expansion of If, with the adhesive material securing the inair in the composite roof structure, this condisulating sheet and the roofing sheet in a softened tion is probably accentuated due to the fact that 4() condition, either a slight air pressure or water the thermal insulation normally contains a cervapor pressure, or a combination of the two, is tain amount of water and water vapor due to the exerted within the roof structure, it results that fact that substantially all of the commercial therthe roofing sheet is separated from the insulation mal insulating materials are of a character which a sheet and-the blisters previously referred to are under normal conditions contain absorbed mois- 15 formed. ture to the extent of at least about 8% by weight The usual roof structure .is one wherein the and in addition to this absorbed moisture the air roof comprises a concrete slab, deck or the like, enclosed within the cellular structure of the inwhich in the construction, serves on the undersulating material carries therewith water vapor side of the roof structure as an air impervious in an amount in accordance with the vapor ten- 5: barr'er whichwill prevent the escapeof air downsion existing under the from time to time exwardly. On this concrete roof slab there is in.- isting temperatures. This moisture contained in stalled a thermal-insulating'matrial such as for the thermal insulating material when heated, say, example, a fiber insulating board, which insulato 120 degrees Fahrenheit, which is commonon tion is usually secured to the upper surface of roofs in the summer time, is more or less vapor- 7, the concrete slab by a hot mopping of asphalt, ized and the roof structure'is subjected to the effect of the combined pressures of the expanded contained air and vaporized moisture.

The object of this invention is to provide a roof construction wherein there is prevented from being built 'up within the structure a pressure greater than atmospheric pressure so that there is no tendency for the roof covering sheet, that is, the saturated roofing felt, to be lifted from the thermal insulating material to which it is adhered, and incidental to such principal objects of the invention there are involved the objects of providing a generally improved roof construction which does not involve complications in its application but which will overcome the principal objections to the use of thermal'insulation embodied in the roof structure directly under the roofing felt surfacing sheet.

The invention is illustrated in the accompanying drawings wherein Figure 1 is a cross-section of a portion of a roof structure, Figure 1A is a detail of a modification of the structure shown in Figure 1, Figure 2 is a worm's eye perspective of the construction illustrated in Figure 1 with a portion broken away, Fig'ure'3 is a section of Fi ure 1 taken on line 3-3, Figure 4 is a, fragmentary section of the roof illustrating a vapor escape means, Figure 5 is a view similar to Figure 4 but showing a modified form of the construction, Figure 6 is a detail of a thermal insulating unit with portions broken away, Figure '7 is a fragmentary elevation of a modified thermal insulating unit, Figure 8 is a fragmentary elevation of a further modified form of. the thermal insulating unit, and Figure 9 is a fragmentary perspective of a still further modification of the thermal insulating unit.

Attention is directed to the fact that while the inventions hereof are generally applicable in a construction including any form of roof deck,

. it is of particular value in connection with these forms of roof deckwherein the roof deck is a tight structure, that is, one which will not allow air to pass downwardly through the roof deck, and that the invention is particularly applicable to a roof deck comprising a concrete or like continuous slab construction, or to any deck to which a continuous vapor-seal is applied before the insulation is laid.

In the roof construction illustrated in the accompanying drawings, a roof deck is indicated at H], such roof deck being shown as a concrete slab but which deck, of course, may be any other usual form of roof deck.

In connection with the roof slab Hi there is indicated the usual parapet wall II and over the slab In there are shown applied thermal insulating units l2. The thermal insulating units 12 may be and preferably are sheets of fiber insulating board such as are regularly available although in accordance with the invention hereof, these sheets are specially prepared as hereinafter described, or instead of comprising sheets of fiber insulation board, the thermal insulation units may be formed of any desired material which will. provide the requisite insulation.

The thermal insulating sheets l2 are preferably adhered to the roof deck ill by mopping the roof deck with hot asphalt whereupon the thermal insulating units l2 are applied to such mopping of hot asphalt before it is cooled so that upon cooling the units i2 are securely adhered to the surface 01" the slab I0. Units i 2 may be of any practical dimensions and preferably they are about 22"x4 and have a thickness of 1", /2". or such other thickness s is determined to be the economical thickness of thermal insulation for use in the particular structure.

The thermal insulation units i2 are formed so that when a plurality of these units are laid in juxtaposition, there are formed intersecting channels comprising a continuous channel net work I! through the thermal insulating material.

The continuous net work of channels I! may be formed in any desired way but the preferred manner in which these are provided is through forming the thermal insulating units as is shown in Figure 6, in which the unit is shown, around its edges on its underside, as rabbeted with an inclined wall as at l4 whereby when a plurality of such units are laid in adjacent relationship there is formed along such meeting edge a channel such as is shown at l in Figures 1- and 2. A modified form of rabbeting the edge of units I2 is shown in Figure 7 wherein the lower part of the unit is rabbeted with a vertical face l5 and a further modified manner for providing the channel net work is shown in Figure 8 wherein the unit I2 is provided around its edges with a V- groove indicated at It. Any oneof the several forms of units illustrated in Figures 6, 7 and 8 will provide the continuous net work of channels l1 and it is readily evident that such channels may be provided by any one of many other forms of channeling, etc., of the units H, as by grooves or channels provided on the under side, not at the edges, if properly aligned with adjacent units.

The units 12 having been applied to roof deck Ill in accordance with the' previously described procedure, a roofing material which may be the ordinary saturated and coated felt roll roofing 23 is applied over the surface of units I2 in accordance with usual practices, that is, successive widths of the saturated roofing material are mopped over the surface of units I2, adhered with asphalt, or the like, with succeeding widths of such saturated roofing overlapped and adhered to one anotheras is usual practice. 4

The usual fiashings 24 are applied at the edges of the roofing 23 which has been laid in accordance with the above description with one edge sealed to the roofing 23 and with the upper ends of such fiashings extending into parapet wall II and appropriately sealed thereagainst in accordance with usual practices. Flashing 24 is provided with slits or openings 25 which is a feature differing from usual practice and further, the flashing is so applied that at and in the vicinity of such slits, the vertical portion of such flashings, that is, the portion extending from the roof surface to the parapet wall, is not adhered solidly to the parapet wall. Over the usual flashing 24 there is applied a secondary protecting flashing which is appropriately secured to parapet wall H and extends down over the vertical portion of the usual flashing 24 to cover the slits 25 but such secondary flashing 26 is not adhered to the 'but may be applied as short sections only of sufficient width to protect the openings 25 in the flashing 24.

The openings 25 in fiashings 24 serve as escape channels for air and vapor coming from the channel net work I! and their action in this respect is as follows:

A roof structure as above described, that is, with an air impervious base such as the slab l0 having the thermal insulating material l2 applied thereto with an air impervious roof covering 23 applied thereover, constitutes, together with the fiashings and parapet wall, and the like, a completely closed system in which there is trapped a certain amount of air and moisture, this being primarily the air contained in the thermal insulating units l2 and the moisture contained in such units and in the slab 10. Such a roof system as it heats up under the action of the sun in the summer time will rise to a temexpands in accordance with such temperature to create a positive pressure exerted between the.

slab l0 and the roof covering 23. In addition to the pressure created through the expansion of the trapped air, moisture which is within the system is vaporized in accordance with the temperature and pressure prevailing, that is, a certain amount of the moisture vaporizes in accordance with the vapor tension of water under the conditions of tension and pressure prevailing, and therefore there is present, within the closed system which has been described, a composite gas which is made up in part of air and in part of water vapor, which composite gas has a pressurecorresponding to the temperature prevailing.

The pressure of the gas within the closed system tends to, due to the fact that the slab I0 is impervious, exert a pressure upon the roofing sheet 23, particularly clue to the fact that the asphalt with which such sheet is ordinarily applied to the insulating material l2 softens at elevated temperatures and has under such condi tions little or no internal strength, causing the surface sheet 23 to pull away from the surface of the insulation I2 and to form distinct blisters raised from the normal plane of the roof.

Due to the fact that the composite roof structure hereof is supplied with the net work channels H, the gases in all portions of such structure are free to flow from one portion thereof to another, and it results that as the pressure within the structure tends to increase due to elevation of temperature, the expanded gases tend to flow through the channels I! until eventually at the edges these expanded gases will escape up behind flashing 24 and out through openings 25 which are provided in the fiashings. Thus the pressure within the system is relieved and there is not the tendency for the roofing 23 to be raised from, the surface of the insulation 12.

A modified form of the construction shown in Figure 1 is shown in Figure 1A. This modified form shown in Figure 1A is in efiect the addition of a check valve to the construction previously described. The construction shown in Figure 1A is substantially the same as that shown in Figure -1 except that insulation sheets l2 and roofing 23 are installed so as to terminate a short distance, say one to two inches from the parapet wall II and the space thus provided is filled with low melting point asphalt or pitch or the like as. indicated at 21. This strip of asphalt 2'! around the edge of the roof acts as a non-return valve.

As the roof structure heats up under the summer sun causing expansion of the gases and vapors within the system, the heat causes low melting point asphalt 21 to soften. As the gases and would be drawn conversely into'the roof structure but in cooling the asphalt 21 will have solidified and will prevent this from occurring and thus the eiTect of a non-return valve on the escape system is achieved.

In large roof areas, it is advisable that addi- I tional vents for the escape of excess pressure be provided, which vents may be supplied as illustrated in Figure 4 or 5 and which may be installed in such number as may be required to provide for the necessary relief of pressurefrom the interior of the system to prevent the loosening of roofing sheet 23 from the surface of the insulation as has been hereinbefore described. The additional vents may be supplied in such number as is .deemed desirable and it is suggested that at least one of such. be supplied for each 5,000 square feet of roof surface, although this is not a fixed matter since the requirement with respect to additional vents depends almost entirely upon the dimensions of the individual channels II, that is, if the rabbeting or the like of the individual sheets I2 is such that the dimensions of the channels will be.small,-the numberof additional vents should be increased, whereas if the dimensions of the individual channels are relatively large, few, if any, additional vents will berequired.

The simplest manner of venting the structure is to provide a vent such as is disclosed in Figure 4 wherein there is shown merely a tube l8 inserted through the roofing sheet 12 and opening into channel H, the upper end of this tubing being bent into an inverted U shape so that rain or the like cannot readilyget into the open end of the tube. The tube, of course, will be suitably flashed where it passes through the roofing sheet 23, such flashing being indicated at IS.

The vents 25, as above described, as well as l8; each provide for free flow of gases into and out of the channel system, that is, if theroof system heats up, the gases may flow out through vents 25 and I8 and conversely as the roof struc;

this water vapor will be condensed into water and thereby become present as water in the roof structure. The presence of water, of course; within the composite roof structure is detrimental in that water as such, particularly should it eventually become present in suflicient amounts, will bring about deterioration of the structure and in addition, the presence of water decreases the efficiency of the insulation.

In lieu of providing the relief vents either in the form of slits 25 in the flashings 24 or as open tubes l8 as disclosed in Figure 4, the vents may be provided in the form as shown in Figure 5 wherein a vent pipe i8 is provided which extends through the roofing sheet 23 with its open end opening into channel system I! and flashed as at i9. This tube I8, instead of being left open at its upper end, is provided with a collapsible airtight bag 20, or alternatively while not shown but as maybe readily understood, it may connect with any other type of container which would correspond substantially to the airtight bag 20, but such container it is, of course, understood, would be sealed so that air could not flow in and out of the container except through tube 18 and constructed so that its volume expands and contracts to compensate for the expansion and contraction of the volume of gases within the roof system without causing appreciable change in pressure, that is, constructed similarly to a gasometer. Collapsible bag 20, secured to the upper end of tube i8 provides an enclosure into which, as may be readily understood, expanded gases from the channel system H may escape and from which, as the gases again contract upon cooling, they may be drawn back into the channel system so that at no time is there any noticeable pressure built up within the roof system nor will it be subjected to any noticeable vacuum since upon tendency for either to occur, the excess air or cated by the dotted portions in Figure 6, after which the unit is immersed in a relatively high melting point asphalt to cause a surface coating to be adhered to the surface of the unit, which surface coating will better adhere because of the initial penetration of the surface with the low melting point asphalt as described. This provision of a sealed unit l2 in accordance with the description thereof just given provides such units so isolated, that should a leak occur in the roof structure there is little or no tendency for the moisture to penetrate into the individual units l2 and, therefore, the detrimental effects of the presence of water in the units will not make itself apparent, and furthermore, should in some manner the water penetrate into one unit then due to the fact that such unit is substantially sealed off from the other units, this moisture will not be distributed to a plurality of the units but will be retained in the individual unit which has been damaged to the extent that the water has been enabled to penetrate thereinto.

In lieu of a surface saturation and coating of the unit i2 with asphalt as above described, the unit may be enveloped in a water impervious membrane such as indicated at 21 in Figure 9 wherein 2! illustrates a water impervious membrane which has been wrapped around the unit i2 and is preferably secured thereto by a layer of asphalt, or the like, adhering membrane 21 to the surfaces of unit [2. This membrane 21 may be either a water impervious saturated felt or it may be a duplex paper, that is, two-ply paper plied with a continuous film of asphalt or the like, or it may be any other suitable water impervious membrane.

Such envelope enclosing insulation unit it, if

membrane 21 is air and vapor proof, should have several small perforations such as 28 venting the enveloped unit to channel system l1 so that pressure may be relieved from within the envelope.

There having been above disclosed in its preferred embodiment and in detail a composite roof construction which embodies a provision for preventing the building up of air pressure between the roof slab and the roofing material and one wherein the construction is novel and useful, we claim: 7

1. A composite roof structure comprising a roof deck, a layer of thermal insulation material comprising a plurality of insulating units on said deck and a finishing roofing material over said layer of thermalinsulation material, the thermal insulation material having extending throughout the layer horizontally thereof a communicating net work of interconnected passages, and said interconnecting passages formed by the juxtaposition of said insulating units.

2. A composite roof structure comprising a roof deck, a layer of thermal insulation material comprising a plurality of insulating units on said deck and a finishing roofing material over said layer of thermal insulation material, the thermal insulation material having extending throughout the layer horizontally thereof a communicating net work of interconnected passages, the such net work of communicating interconnected passages vented to the exterior of such composite struc-' ture, and said network of communicating interconnected passages formed by the juxtaposition of said insulating units,

3. A composite roof structure comprising a roof deck, a layer of thermal insulation material comprising a plurality of insulating units on said deck and a finishing roofing material over said' layer of thermal insulation material, the thermal insulation material having extending throughout the layer horizontally thereof a communicating net work of interconnected passages, said communicating network of interconnected passages formed by the juxtaposition of said insulating units, there being provided escape channels forming a means of communication from the net work of communicating passages to the exterior of the composite roof structure.

4. A composite roof structure comprising a substantially air tight roof deck, a thermal insula-,

tion course secured thereon, such thermal insulation course comprising a plurality of units, each unit enveloped in a waterproof enrobement and each unit recessed around its periphery, the such course secured thereon, such thermal insulation net work of connected passages throughout the area of the thermal insulation course, a substantially airtight weather resistant roof surfacing .m'aterial secured on the upper surface of the v thermal insulation course, an extensible airtight container positioned adjacent the roof structure, and a venting passage connecting the airtight container and the net work of communicatin passages.

7 A composite roof structure comprising a roof deck, a thermal insulation course thereon comprising a plurality of insulating units, and a sub-J stantially airtight roof surfacing material thereover, an air conveying passage extending throughout the area of such roof structure and serving to equalize gaseousv pressure throughout such roof structure, said airconveying passage formed by the juxtaposition of said insulating units, and a connection from said air conveying passage to the exterior of said composite roof structure.

8. An insulated roof construction comprising a structure having a roof deck, parapet walls around the roof deck, a course of thermal insulation secured on the roof deck, a continuous weather resistant roofing secured on the upper surface of the thermal insulation course, the thermal insulation course having therethrough a system of communicating passageways, flashing secured around the edge of the roofing to its upper surface and sealed to the parapet wall, the flashing having therein vents, thevents incommunication with the system of communicating.

passageways, and a secondary protective flashing secured to overhang the vents.

9. A composite roof structure comprising a roof deck, a thermal insulation course thereon, and a the periphery of the insulation course and the confining wall.

10. A composite roof structure comprising a substantially air-tight roof deck, a thermal insulation course secured'thereon, the thermal in- Y sulation material having extending throughout the layer horizontalLv thereof a communicating, network of interconnected passages, and a chamber connected tov said network of interconnected passages and adapted to expand and contract, whereby the air pressure within said network is equalized.

11. A ccmposite roof structure comprising asubstantially air-tight roof deck, a thermalinsulation course secured thereon, the thermal insulation material having extending throughout the layer horizontally thereof a communicating,

network of interconnected passages, and an extensible air-tight container connected to said net- I sembly in a composite roof structure, and said work of interconnected passages, whereby the air pressure within said network is equalized.

12. A composite roof structure comprising a roof deck, a thermal insulation course thereon, and a substantially air-tight'roofing'thereover, 5 air conveying passages which within said roof structure serve to substantially equalize gaseous pressure therethrough, and means adapted for releasing the air pressure within the air conveying passages but preventing atmospheric air from returning thereto.

13. A composite roof structure comprising a roof deck, a thermal insulation course thereon, and a substantially air-tight roofing thereover,

air conveying passages which within said roof 15 structure serve to substantially equalize gaseous pressure therethrough, and self-sealing means adapted for releasing the air pressure within the air conveying passages but preventing atmospheric air from returning thereto.

14. A' composite roof structure comprising a roof deck, a thermal insulation course thereon, and a substantially air-tight rooflng thereover, air conveying passages which within said roof structure serve to substantially equalize gaseous pressure therethrough, and self-sealing means adapted for releasing theair pressure within the air conveying passages but preventing atmospheric air from returning thereto, said self-sealing means comprising a substantially low melting point fluent material.

15. A flashing construction adapted for a composite roof structure having air communicating passages throughout, comprising venting means for said air communicating passages, and said' venting means adapted to communicate with the aforesaid air communicating passages and the atmosphere.

16. A thermal insulating unit adapted for asunit recessed about its periphery; whereby, when said unit is assembled in a composite roof structure, a communicating network of interconnecting passages is formed for venting said composite roof structure.

17. A composite roof structure comprising a plurality of thermal insulating units, 'each of said units recessed about its periphery and adapted] when assembled in juxtaposition to each pther to form a communicating network of interconl0 nesting passages for venting said composite roo structure.

18. A composite roof structure comprising a plurality of thermal insulatingunits. each of said units being waterproofed, said units adapted" when assembled in juxtaposition toeach other to form a communicating network of intercon:

necting passages for venting said roof structure, and each waterproof unit disposed within a waterproof pocket formed by adjacent units; 60

whereby, if'moisture enters a'damaged unit, it is not transmitted to adjacent units. 7

19. A composite roof structure comprising a plurality of thermal insulating units, each of said units enveloped in a water impervious membrane,

each of said units recessed about its periphery and adapted when assembled in juxtaposition to each other to. form a communicating network of interconnecting es for venting said composite roof structurefand means provided for each unitenveloped in a water impervious membranefor venting the interior thereof to the comf municating network.

- GEORGE iii. 'SWENSON.

, JR. I6

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