Q: When building with structural insulated roof panels, how far is it safe to cantilever (or project) the ends of a panel past the top plates? I like the idea of creating a protective overhang for the siding and windows.
Last year we completed a SIP roof deck using two kinds of panels. Some were the standard OSB-foam sandwich panels, and some had prefinished T & G pine ceiling boards attached to the bottom. During installation, we noticed a small gap between the panels with the attached T & G ceiling, because the pine boards were slightly wider than the OSB. The panel maker provided us with a foam gasket to seal the gap, which we supplemented with caulk. This past winter, whenever it was cold enough, a line of frost would appear on the shingle roof along the panel joints. The frost line occurred on both types of panels, so we don't think it is being caused by air leakage at the gasketed joints. Should we be concerned?