Abstract:
An improved roof and method wherein each course of slate is underlaid with an interlayment material layer such that the interlayment material acts as a base to the through joints, resulting in a reduction in the amount of slate used by approximately 40% to 50%. The slate meets side to side (the through joint), the underlaying interlayment material providing sufficient waterproofing to protect the roof as well as being of lighter weight and a more economical slate roof than the slate which it replaces.

Description:
FIELD OF THE INVENTION 
     Roofs, more particularly slate roofs, with an interlayment layer between courses of slate and a method of making slate roofs. 
     BACKGROUND OF THE INVENTION 
     Slate roofs are appreciated for their aesthetic and durable qualities. However, they are expensive and the weight of the slate is quite high compared to composition shingles; and, as a result, they are typically two to four times more expensive as composition asphalt roofing. Thus, utility lies in any application of slate on a roof which will reduce the amount of slate needed to effectively cover a roof. Applicants&#39; method and slate roof herein provide for such utility. 
     A good background for slate roofing and the method for installing the same may be found in the NRCA Roofing and Waterproofing Manual—4th Edition, pp. 1179-1227, that document being incorporated herein by reference. Typical slate roofs are constructed in the manner set forth in FIG. 1, labeled “prior art”. With reference to FIG. 1, it is seen that a wood roof is first covered with an underlayment layer, typically asphalt felt paper, to which overlapping slate courses are applied with slate covering the roof in two plies except where there is overlap, in which case there are three plies of slate. Through joints should not occur from the slate roof surface to the felt. 
     Applicant, however, has removed a slate layer and replaced it with heavy-duty, weatherproof interlayment material layer, typically plastic 20 to 60 mil in thickness. 
     SUMMARY OF THE INVENTION 
     In Applicants&#39; improved roof and method illustrated in FIGS. 2 to  6  attached hereto, each course of slate is underlaid with an interlayment material layer such that the interlayment material acts as a base to the through joints. This reduces the amount of slate used by approximately 40% to 50%. Moreover, where Applicants&#39; slate meets side to side (the through joint), the underlaying interlayment material provides sufficient waterproofing to protect the roof. The interlayment material is also less expensive and lighter weight than the slate it replaces. 
     Applicants&#39; present invention improves upon all prior art slate roofs by providing for a markedly improved weather barrier, lighter weight, and more economical slate roof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a prior art slate roof with two plies of slate over the underlayment material (three plies on overlap); 
     FIG. 2 illustrates Applicants&#39; improved roof with an interlayment material between the slate courses and between the slate courses and between the slate courses and the underlayment material. 
     FIG. 3 is a perspective view of Applicants&#39; slate roof featuring interlayment material between slate courses. 
     FIG. 4 is a perspective cross-sectional view of Applicants&#39; slate roof illustrating the use of an interlayment material layer between slate courses. 
     FIGS. 5 a - 5   c  are elevational views of additional features of Applicants&#39; slate roof. 
     FIG. 6 is a perspective view of yet an additional feature of Applicants&#39; slate roof. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Applicants&#39; method utilizes some of the same steps of the prior art in preparing a unique slate/interlayment roof ( 10 ). With reference to FIGS. 1-4, it is seen that a starter strip of wood ( 12 ), about the thickness of a slate tile ( 14 ), is typically used for the first course ( 16 ). Underlaying the first course ( 16 ) at the leading edge thereof ( 16 A) is a sheet of interlayment material ( 18 ), typically 12″ to 18″ long (LI) and about 30 mil. The first course of slate ( 16 ) is laid on top of the starter strip ( 12 ) and fastened to the roof base deck ( 12   a ) over a first course ( 17 ) interlayment material ( 18 ) with nails ( 22 ) driven through the slate and interlayment material as well as through the felt underlayment. 
     The next step is to apply the second course ( 23 ) of interlayment material ( 18 ) by overlapping approximately 2″ to 3″ over the top of the trailing edge ( 16 B) of the first course of slate ( 16 ). The interlayment material ( 18 ) is then fastened to the roof through the use of staples ( 26 ) or the like. The next step is the fastening of the second course of slate ( 24 ) to the roof in a manner known in the trade by driving nails ( 22 ) therethrough. The individual slate tiles ( 14 ) of this second course ( 24 ) are placed with their leading edges ( 24 A) flush or slightly overlapping (⅛″ to ¼″) with the leading edge ( 23 A) of the second course ( 23 ) of interlayment material and abutted one against the other. Additional courses of interlayment material and shingles are applied in this manner with alternating layers of the interlayment layer and shingles. 
     The resulting cross section is a roof with a single thickness of slate tiles except on the overlap portion ( 28 ), where there is a dual thickness of slate tiles ( 14 ). However, at all points the slate is underlaid by an interlayment material ( 18 ). 
     The characteristics of the interlayment material are that it should be of sufficient thickness and durability such that it will not break down when exposed to weathering. A UV resistant interlayment material is advisable. For example, a thermoplastic elastomer or high-density polyethylene, such as those used in geomembrane barriers, is appropriate. Further, single-ply rubber roofing membrane may be used as an appropriate interlayment material. The following may also be used: thermoplastic olefin, high-density polyethylene, thermoplastic elastomers, ethylenepropylene-diene, monomer, polypropylene, and styreneethylene-butadiene-styrene or any other suitable material. 
     Typical widths ( 30 ) of the interlayment material are such that it will extend at least 2″ to 3″ beyond the trailing edge of the overlaying slate in overlap ( 29 ). It may come in 25′ to 100′ rolls and is cut to whatever length is needed. If it is necessary to use more than one piece of interlayment material per course, a side-to-side overlap of about 6″ is recommended. 
     On prior art roofs, the length of the slate tiles is the exposure ×2 plus about 3″. For example, typical prior art slate tiles are 9″×18″, which gives an effective exposure of about 7.5″. Applicants&#39; slate tiles, however, can achieve the same 7.5″ exposure with a 9″ piece of slate. the width of Applicants&#39; slate tiles may be the same as the prior art (typically 6″ to 12″) or any other appropriate width. 
     FIGS. 5 a - 5   c  illustrate additional features of Applicants&#39; present invention. FIG. 5 a  illustrates a slate tile with predrilled holes ( 30 ) with and marked or scored ( 32 ) for alignment and positioning of interlayment overlap ( 29 ). 
     FIG. 5 a  also shows slate side members or wings ( 34 ) attached to the underside of the slate tile for additional through joint weather protection, typically being made of rubber, plastic, or asphalt/fiberglass material. 
     FIG. 5 b  illustrates a double-sided adhesive tape strip ( 36 ) attached to the underside of a slate tile adjacent the trailing edge thereof to hold the tile temporarily in place while it is being nailed to the roof. 
     FIG. 5 c  illustrates the use of adhesive strips ( 36 ) on the interlayment material to assist in holding the slate in place during installation. 
     FIG. 6 illustrates a modification of the interlayment material featuring a flap member ( 18 A) attached to the underside thereof to act as a water trap for protection against wind-driven rain. 
     This flap ( 18 A) at the lower course boundary of the interlayment material should abut the top edge of the underlying slate course to provide a water trap should any water be driven up underneath the shingle. 
     Terms such as “left,” “right,” “up,” “down,” “bottom,” “top,” “front,” “back,” “in,” “out,” and like are applicable to the embodiments shown and described in conjunction with the drawings. These terms are merely for purposes of description and do not necessarily apply to the position or manner in which the invention may be constructed for use. 
     Although the invention has been described in connection with the preferred embodiment, it is not intended to limit the invention&#39;s particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalences that may be included in the spirit and scope of the invention as defined by the appended claims.