Ask Katie: Thoughts on roofs and roof/wall-height relationships

Q: My husband and I are building a new house and are confused by roof pitches and wall heights. Does the roof pitch have a relationship to wall height?

Cathy from Hammond, LA

For having her question selected for this post, Cathy is receiving a complimentary set of KHS photo note cards.

A: Often it does. Roof slopes and the relationship of the roof to wall height (relative to the floor and ground) are critical to a successful design. Often the roof and its disposition are the most defining characteristics of a home.

roof slope 101
For the sake of discussion, let’s say there are three roof-slope categories. I consider a lower slope to be 7/12 and below. A steeper slope is 10/12 and above. A mid-range slope is everything in between. Think of roof slope in terms of rise and run. A 4/12 slope means that for every 12-inch horizontal run, the roof slope rises four inches.

Roof slope is partly a function of climate, available roofing materials, and structural considerations. The steeper the roof slope is, the easier for accumulated snow or water to slide or run off. So, wetter, snowier climates tend to have steeper roofs. Materials that perform well on a steeply sloped roof may be problematic on a roof slope below 4/12. Don’t forget that the primary role of the roof is to provide overhead protection from the elements. Roof slope can also have structural implications, with flatter roofs having different requirements than more steeply sloped roofs. Some roof/wall-height relationships can trigger other structural considerations too.

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