Decks (Cont'd)

In addition, the lengths of the nails may be chosen to prevent the points from protruding through the deck where they may mar the inside face. If ice damming is a potential problem or if reverse condensation is likely to occur, such as may be encountered in an ice arena, the cold weather roof system should be used in conjuction with horizontal strapping, and ventilation must be provided at the eaves and at the peak.

In buildings such as ski cabins that may be subjected to heavy snow loads, it is usually necessary to fasten wood members (typically 2" X 4"(50.8 mm X 101.6 mm) on edge from ridge to eave on the roof deck and place the rigid insulation between.

Strapping is then applied across the top of these members, giving a ventilated air space and avoiding compression of insulation (Figure 24). The need for strapping can often be completely eliminated by the use of false plywood deck, immediately over the insulation, to which the shingles or shakes are directly fastened (Figure 25).

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