US3862527A

US3862527A - Roof construction

Info

Publication number: US3862527A
Application number: US369829A
Authority: US
Inventors: Charles M Peterson
Original assignee: Harry S Peterson Co Inc
Current assignee: Harry S Peterson Co Inc
Priority date: 1973-06-14
Filing date: 1973-06-14
Publication date: 1975-01-28
Anticipated expiration: 1992-01-28

Abstract

A roof construction for flat roof industrial buildings and the like wherein the roof deck comprises a plurality of structural members such as prestressed concrete tees or slabs disposed in side-by-side abutting relationship on top of and spanning the walls of a building. Small cracks in and joints between the concrete members are discretely filled and sealed using an elastomeric sealant material. Rigid polystyrene foam boards are placed on top of the concrete members without the use of any adhesive or other sealing membrane. The edges of the polystyrene board may be staggered between layers so that the edges or seams between the adjacent boards do not line up. Finally, a layer of crushed stone is placed on top of the polystyrene boards to weight them down and prevent ultraviolet ray damage. An aluminum angle member is secured around the periphery of the roof deck to maintain the roof construction components in place. In the illustrated embodiment, a line of windows is secured by means of aluminum strips in the space between the tops of the walls and the roof deck.

Description

Peterson [111 3,862,527 [451 Jan/28, 1975 I 1 ROOF CONSTRUCTION [75] Inventor: Charles M. Peterson, Franklin,

Mich.

[73] Assignee: Harry S. Peterson Company,

Pontiac, Mich.

[22] Filed: June 14, 1973 [21] Appl. No.: 369,829

[52] US. Cl 52/94, 5 2-/262, 52/302, 52/309, 52/408, 52/747 [51] Int. Cl. E04d 3/26, E04d 3/32 [58] Field of Search 52/302, 262, 303, 60, 309, 52/409, 410, 94, 95, 408, 747

OTHER PUBLICATIONS Architectural Catalog File, Sweets Catalog Service, 1962, 2h/LI, (pages 2 & 3), 2h/Ra, pages 2 & 3. Architectural Catalog File, Sweets Catalog Service, 1970, 8b/DOW,,pages 1-18.

Primary Examiner-John E, Murtagh Almrney, Agent, or Firm-Thomas N. Young [57] ABSTRACT A roof construction for flat roof industrial buildings and the like wherein the roof deck comprises a plurality of structural members such as prestressed concrete tees or slabs disposed in side-by-side abutting relationship on top of and spanning the walls of a building. Small cracks in and joints between the concrete members are discretely filled and sealed using an elastomeric sealant material. Rigid polystyrene foam boards are placed on top of the concrete members without the use of any adhesive or other sealing membrane. The edges of the polystyrene board may be staggered between layers so that the edges or seams between the adjacent boards do not line up. Finally, a layer of crushed stone is placed on top of the polystyrene boards to weight them down and prevent ultraviolet ray damage. An aluminum angle member is secured around the periphery of the roof deck to maintain the roof construction components in place. In the illustrated embodiment, a line of windows is secured by means of aluminum strips in the space between the tops of the walls and the roof deck.

5 Claims, 3 Drawing Figures ROOF CONSTRUCTION INTRODUCTION This invention relates to a roof construction for industrial buildings and more particularly to a roof construction of the type having external insulation.

BACKGROUND OF THE INVENTION The typical industrial roof construction involves the building of structural support systems for wood or steel, the building of a roof deck, scaling the deck with a full covering of asphaltic meterial and the insulation of the deck by disposing heat retaining material over the inside surface of the deck. More recently it has been recognized that insulation may be positioned on the outer surface of the roof deck and covered with stone to weight the insulation down and protect it from ultraviolet ray damage. One of the benefits provided by this inverted" roof structure is the maintenance of the sealing layer at a relatively even temperature. An example of such an inverted" roof structure is described in detail in the US. Pat. No. 3,41 1,256 to John S. Best.

In the Best patent, the roof deck is first covered with a water-impermeable membrane comprising a plurality of alternating layers of felt and bituminous material. This water-impermeable membrane is then covered with blocks of rigid polystyrene or the like. The polystyrene is adhesively secured to the membrane and is in turn covered with stone. According to the Best patent, the disposition of the insulation over the waterimpermeable membrane maintains the membrane at a relatively constant temperature and, thus, avoids the BRIEF SUMMARY OF THE INVENTION In accordance with the present invention, an mverted" roof construction is provided wherein the heat insulating material is on the outside of the roof deck but wherein the mass sealing of the deck with an asphaltic membrane is eliminated. The elimination of the asphaltic membrane itself results in a number of advantages including substantial cost savings, reduced fire evenness often found in jointed roof decks. Moreover,

the selective sealing of the roof structure is perferably carried out using a high-recovery, chemically curing sealant of the polymeric type, thus, providing substantial improvement over asphaltic materials from the standpoints of increased flexibility and resistance to long-term dillution from water immersion.

In general. the objects of the present invention are accomplished by constructing the roof deck from prestressed concrete members which. in the typical situation, span the walls of the building to be roofed, the prestressing being along a single axis and eliminating all shrinkage cracks so as to effectively render the concrete structure impervious to moisture and to permit long spans. Where two or more prestressed concrete structural members are required to form the deck, such, members are disposed in abutting relationship and the joint between such member is permanently sealed using a resilient polymeric sealing compound of a type hereinafter described in detail. The insulating material, preferably in the form of one or more layers of extruded, closed-cell polymeric foam material, such as polystyrene, is placed directly on the prestressed concrete structural member and is then weighted down and protected from ultraviolet ray damage by a layer of crushed stone.

In the preferred embodiment of the invention, the prestressed concrete structural members which form the deck take the form of unidirectionally prestressed concrete tees which are placed in side-by-side relationship and sealed along the joints thereof. Any cracks in the members are discretely sealed rather than by mass coating. According to this preferred construction, a space is defined between the upper extremities of the building wall and the surface of the roof deck, this space being such as to readily accommodate a line of windows or other structural elements as suits the designer. Moreover, thepreferred embodiment comprises a rigid L-shaped angle disposed around the periphery of the roof deck so as to retain the insulation material as well as the crushed stone. As hereinafter described in greater detail, the retainer angle is periodically interrupted by scuppers to permit water to flow from the roof deck.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an industrial building having a flat roof constructed in accordance with the invention;

FIG. 2 is a cross-sectional view of a portion of the roof construction in the building of FIG. 1; and,

FIG. 3 is a plan view with layers broken away of the roof construction of FIGS. 1 and 2 to illustrate the various layers and the disposition of the elements thereof.

DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENT OF THE INVENTION Looking now to FIG. I, there is shown an industrial building 10 having

concrete walls

12 and 14 and a flat roof construction 16 of the inverted type as hereinafter described in detail. In the building 10 of FIG. 1, a peripheral line of windows 18 is disposed between the top of the

walls

12 and 14 and the roof construction 16. This structural arrangement affords excellent interior lighting conditions, but it is to be understood that other structural components, such as brick, wood, and other materials can be substituted for the windows 18.

Looking specifically to FIGS. 2 and 3, it can be seen that the roof construction 16 of the building 10 comprises a plurality of prestressed concrete tees 20 having depending vertical leg portions 22 and flat deck portions 24. The two concrete tees which are shown in FIG. 2 span the entire distance between a pair of opposite walls 12 and are supported on the walls by means of neoprene bearing blocks 26. In addition, the deck portions of the two concrete tees 20 are placed in sideby-side abutting relationship so as to form a linear butt joint 28. Any cracks formed in the tees 20 during shipping are discretely filled with sealant after being dressed and primed as necessary. The joint 28 is preferably formed such by dressing into a V-shape and filled with a weather resistant sealer 31 to prevent moisture from penetrating the roof deck. The sealant material used in the cracks and joints .is preferably a durable, elastomeric, one or more component sealant conforming to federal (G.S.A.) specifications TT-S-OO23OC (one component) or TT-S-()()227E (two component). Such sealant materials should exhibit long-term flexibility to withstand differential expansion and contraction of the tees 20, and long-term adhesion to concrete after extended water immersion; thus, the sealant should contain no water-extractable ingredients. Suitable sealant materials include chemically-curing polyurethanes and polysulphides having extension recovery properties of IS to I percent. based on a 25 percent extension test. A suitable sealant material is available from the Harry S. Peterson Company of Pontiac, Michigan, and is marketed under the trade name ISO- FLEX". The V-shaped slot in the joint 28 may be formed and sealed in accordance with the teachings of the copending U.S. patent application, Ser. No. 292,0l9, filed Sept. 25, 1972 in the name of Harry S. Peterson, Charles M. Peterson, and Robert King.

In accordance with the present invention, the concrete tees are prestressed in the conventional fashion by means of tension cables which extend unidirectionally from one end thereof to the other, thereby placing the tees in compression over the span between the walls 12. This prestressing places the concrete in uniform compression eliminating shrinkage crack formation and renders it substantially impermeable to moisture and, in addition, permits long spans of unsupported roof deck to be utilized. As hereinafter described, any cracks which might develop in shipment are discretely filled and, assuming a good quality sealant is used, good results may be expected since such cracks are non-moving in character. Moreover, uneven joints resulting from differential camber and loading are filled with the flexible sealant so as to provide a smooth ramp like surface from one tee surface to the next, the ramp of the sealant filler bridging the tees being preferably extended out to overlap the lower tee surface.

In accordance with the invention, the flat deck surface which is formed by the upper or external surfaces of the perstressed concrete tees 20 is covered with two or more loosely disposed plies 30 and 32 of rigid closed-cell polymeric material. such as extruded polystyrene board, so as to provide heat insulation in the roof construction. The present invention does not contemplate the use of any adhesives, as required in the prior art, to be applied to the insulative material during installation. Rather the blocks 30 are laid directly upon the sealed flat deck surface 24 of the concrete tees 20. Additional layers 32 are similarly disposed directly upon the preceding layer 30 without bonding the layers together. As shown in FIGS. 2 and 3, the

plies

30 and 32 comprise two-by-eight foot boards of /2 to 4 inches in thickness and are overlayed such that the edges or seams do not line up. This staggering overlay maximizes heat insulation by reducing leakage at the butt joints. It is to be understood that a single ply or more than two plies of insulating material may be employed without departing from the substance of the present invention. the dimensions previously given as well as the use of two or more staggered plies being preferred, but not critical to the invention. It is, however, important that a rigid, extruded closed cell material be used to endurc the exposure to weather. It has been found, for example, that the compressed bead insulation board deteriorates rapidly when exposed to intermittent water immersion and, thus, is not suitable for use in the present invention.

Next a layer 34 of crushed stone or aggregate is placed over the polystyrene insulation board plies to prevent damage from ultraviolet rays and to prevent movement ofthe insulation board due to wind. The size and weight of the aggregate to be used may vary according to building design, wind force and whether or not any adhesive is used between the roof deck and insulation board plies. Wind may cause variable amounts of uplift force at various points over the roof. the most severe forces tending to occur at the'corners of the building. Accordingly, it is desirable to place an arrangement of heavy cast concrete or stone blocks 35, commonly called patio blocks over the insulation board at the building corners as shown in FIGS. 1 and 2. This also eliminates the erosion-like effect of wind and weather which sometimes occurs in the aggregate at the corners. The stone blocks 35 may alternatively beplaced all around the perimeter of the roof.

In general, an aggregate weight of IO to 15 pounds per square foot is normally adequate to weight down the insulation board. Patio blocks of about 2 inches in thickness are also adequate. In an actual embodiment. the following aggregate specification was used and has been found satisfactory in a system using two plies of Styrofoam board which are not adhesively bonded to the roof deck or to one another; cut limestone having a composition or gradatious as listed below:

passing a screen size l/z in. 92-l()0% passing a screen size 1 in.

40- 7571 passing a screen size 4 in. l5 35% passing a screen size 2 in.

()- 15% passing a screen size Vs in. 0- 5% passing a screen size No.4

l /r maximum passing a screen size Wash.

It is to be noted that the ply 30 of insulation board is not bonded or otherwise adhered to the upper surface of the concrete tees 20, the top ply 32 is not bonded to the lower ply, and that the concrete tees are not sealed by a full surface coating of asphaltic or similar material. The use of uniaxially prestressed deck spans eliminates the need for an adhesive bond or full surface sealant layer between the insulation and the prestressed concrete tees. The elimination of the asphaltic sealer membrane improves the fire rating of the subject roof over prior art roofs by elimination of the possible melting and combustion of the asphaltic or coal tar type ingredients of prior art roof-sealing membranes. It also facilitates the location of any leaks which might develop in the roof deck since such leaks will show through the underside of the tees almost directly beneath the acutal leak point. In a membrane covered roof deck, leaks can travel horizontally a great distance. In addition. the loose construction illustrated herein greatly facilitates repair as the aggregate and insulation board plies may simply be removed to bare the surface of the roof deck.

As illustrated in the drawings, an L-shaped aluminum angle 36 is secured such as by drilling and/or nailing around the periphery of the roof deck. The angle 36 serves to retain the

layers

30 and 32 of insulation board as well as the layer 34 of crushed stone. The angle 36 is discontinuous; i.e., is provided with breaks 38 in the upstanding or vertical portion thereof to provide water runoff from the flat roof. Small scuppers 40 may be provided simply by striking out the breaks 38 and bending the material downwardly. Alternatively, the channel 36 may be made up of sections which are simply left a small distance apart and a spout or spillway-shaped scupper may be brazed or welded into the gap.

As best shown in FIG. 2, aluminum angles 42 and 44 may be secured, such as by bonding with a bead of the polymeric sealant material, around the periphery of the vertical opening between the top of the

walls

12 and 14 and the lower surface of the concrete tees t0 accommodate the glass window panel 18. As previously mentioned. this is an optional structural arrangement and may be replaced with other forms of structural means where such means are preferred by the designer.

It is to be understood that the present invention provides many advantages in fabrication, maintenance, repair, and disassembly not expressly listed herein. It is to be further understood that various modifications and additions to the subject invention as illustratively described herein may be made. It may, for example, be preferred to build the roof deck from single leg concrete tees or hollow core concrete slabs or to form the

walls

12 and 14 from materials other than concrete. In addition. the aesthetic appearance of the building 10 of FIG. 1 in no way forms a part of the present invention except to, the extent that it results from the structural arrangement hereinbefore described in connection with the preferred embodiment of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An insulated roof construction for a building having walls and a roof structure characterized by the absence of a mass waterproofing membrane covering the roof structure and comprising: at least two precast concrete members spanning the walls and defining at least one intersection joint wherein the members are in rea sonable proximity to one another, a flexible polymeric sealant spanning the joint and substantially adhering to the concrete structures on opposite sides thereof, a layer of relatively light and substantially non-sealing thermally insulative material freely disposed directly on the concrete members, and a layer of particulate weighting material disposed over the insulative material layer and of such thickness as to protect the insulative material from exposure and to prevent the insulative material from movement due to wind.

2. The insulated roof structure defined in claim 1 and further including an angle member disposed around the perimeter of the roof to contain the insulative material and particulate material.

3. The insulated roof structure defined in claim 2 wherein the angle member is discontinuous to allow water to escape the surface of the roof.

4. The insulated roof structure as defined in claim 1 wherein the insulative material is a rigid foamed polymeric material such as polystyrene.

5. A method of fabricating a roof structure characterized by the absence ofa mass sealing membrane covering the structure and comprising the steps of: constructing a roof structure by placing a plurality of prestressed concrete deck members in side-by-side relationship between support means with the axes of prestress in parallel alignment to define at least one intersection joint between said members, discretely filling any cracks in said members, sealing the joints between said members with a moisture-impermeable flexible polymeric sealant material, curing the sealant material to adhere to the members on opposite sides of each of such joints, placing at least one ply of substantially rigid polymeric insulation material on the outer surface of the deck members and covering the insulation material with a particulate weighting material.

Claims

1. An insulated roof construction for a building having walls and a roof structure characterized by the absence of a mass waterproofing membrane covering the roof structure and comprising: at least two precast concrete members spanning the walls and defining at least one intersection joint wherein the members are in reasonable proximity to one another, a flexible polymeric sealant spanning the joint and substantially adhering to the concrete structures on opposite sides thereof, a layer of relatively light and substantially non-sealing thermally insulative material freely disposed directly on the concrete members, and a layer of particulate weighting material disposed over the insulative material layer and of such thickness as to protect the insulative material from exposure and to prevent the insulative material from movement due to wind.

5. A method of fabricating a roof structure characterized by the absence of a mass sealing membrane covering the structure and comprising the steps of: constructing a roof structure by placing a plurality of prestressed concrete deck members in side-by-side relationship between support means with the axes of prestress in parallel alignment to define at least one intersection joint between said members, discretely filling any cracks in said members, sealing the joints between said members with a moisture-impermeable flexible polymeric sealant material, curing the sealant material to adhere to the members on opposite sides of each of such joints, placing at least one ply of substantially rigid polymeric insulation material on the outer surface of the deck members and covering the insulation material with a particulate weighting material.