Snow load removal

DETAILED DESCRIPTION Referring to FIGS.
1 and 5, in building 25 on concrete foundation 26, a base layer of self-extinguishing reinforced plastic film 2 is stretched over a steel cage consisting of vertical and horizontal frame members such as tubes 1 and 7 respectively, so as to exert a substantial resistance to surface pressure.
Tubes 1 and 7 provide substantially relatively rigid means to support layer 2 in relatively substantially fixed position from other portions of the building.
Over film 2 is placed an insulating layer of flexible elastically deformable compressible distensible material such as an 11-inch nominal thickness resilient glass mat.
, 3, and finally over this a flexible foldable layer 6 consisting substantially of weather resistant polypropylene film, three-film ply, reinforced by two layers of high strength fiber such as steel, glass, polyester, polyurethane or nylon fiber, or their mechanical equivalent.
This outer film 6 may be pigmented with an ultraviolet absorbent pigment such as zinc oxide or carbon black, and covered by a coating of a flaky reflectant or UV absorbent material such as aluminum, mica or glass, suspended in a weather resistant binder, such as an acrylate or methacrylate polymer of consistency suitable for such a coating application.
A three-ply fiber reinforced polyethylene film known as "Griffolyn 5" made by Griffolyn Co.
, Inc.
, was used as that outer skin of the roof.
The weight of this film was 0.
72 ounces/ft.
.
sup.
2.
We could also use a two-ply reinforced polyethylene film known as "Griffolyn 55", weight 0.
385 ounces/ft.
.
sup.
2 or a quadruple layer of similar film weight 1.
01 ounces/ft.
.
sup.
2.
Unreinforced film could also be used, so long as it is flexible, foldable, and capable of holding a stationary pressure of at least 20 lbs.
/ft.
.
sup.
2.
Inclusion of sound proofing dense granules or ribbons could further increase the weight of the film, however, it should remain sufficiently light not to cause by its own weight a compression of more than 25% of the roof thickness and preferably not more than 10%