Framing a Cold Roof
Preventing roof leaks caused by ice damming.
Synopsis: The author explains how he builds a double-layer roof that allows unimpeded air flow from eave to ridge, keeping the roof deck cold and preventing ice dams. Sleepers consisting of 2x4s on edge separate the two roof decks.
When I moved to Idaho’s snow country after living in southern California and Hawaii, I had to learn a number of regional differences in construction. For one thing, it gets colder here, so we use 2×6 studs (at least) to accommodate R-19 insulation in the walls; R-30 is the minimum in our ceilings. I also learned to build what’s known as a cold roof. Such a roof, paired with a Boston ridge vent, prevents ice damming and roof leaks.
The scenario for a leaky conventional roof in snow country goes like this. With temperatures below freezing, snow accumulates on the roof over a vaulted ceiling. Even if the roof…