Hip-Roof Framing Made Easier
Measure from the rafter's bottom edge for exact layout.
Synopsis: North Carolina builder John Carroll dissects the process of building a hip roof and discusses his technique for rethinking this complicated piece of construction. Using the roof of a small outbuilding as an example, Carroll first locates the six king common rafters, then uses a table of rafter multipliers to determine the common-rafter lengths. He then determines the run and length of the hip rafters and jack rafters. Full-color illustrations accompany the article, highlighting Carroll’s hip-roof process.
Framing a hip roof is a head-scratcher for most carpenters, but it doesn’t have to be. The process became a whole lot easier for me when I realized that the primary challenge in building a hip roof is one of layout, not math. And the key to layout is to know exactly where to begin and end measurements.
In my approach, all the measurements are along the bottom edge of the rafter, short point to short point. This is not the way I learned how to do it, but once I started thinking about the bottom plane of the rafters instead of the top (or instead of some theoretical middle line), everything fell into place. Because I measure and mark along the bottom of the rafters, where I measure to is where I cut from; and because there are fewer steps, there are fewer chances for mistakes.
Another advantage of my approach is that I don’t have to deal with dropping the hip because I use the same dimensional lumber for all the rafters and I align the bottom edges. On this roof, I used 2×6 lumber for the hips, jacks, and commons. This left the tops of the jacks 1 ⁄4 in. above the hip, which allows the sheathing to clear the hip and allows air to flow over the hip and up to the ridge vent. If I had wanted to have both the bottom and top edges in plane, I could have ripped down a 2×8 to a width of 5-3 ⁄4 in.
I also don’t have to make adjustments for measuring from the center of the board because I take all my measurements from the edge of the board.
The other thing I do that’s a little different is that I put down my English measuring tape when I finish framing the walls and pick up a metric tape to frame the roof. In my approach, the metric system is easier to use when math is involved because there are no fractions to deal with. The math itself is simple to calculate because every rafter position and measurement can be explained with right triangles and dimensions that are based on the Pythagorean theorem.
Before I consider any of this, though, the first thing I do on a new job site is get acquainted with the details and visualize how the parts fit together. The project shown here is a simple storage shed. Because the roof is small and all the framing is 2×6 dimensional lumber, I don’t have to make adjustments for a larger ridge beam or hip rafters.
Two tools make the job easier
First, I make a story stick out of a 2-in.-wide rip of plywood. I lay it on the top plate of the end wall and mark out the common-rafter run, the wall thickness (for the seat cut), and the eave overhang. The beauty of the story stick is that I can have all the initial measurements I need to frame the roof in one place. Then I can take the story stick down to the cut station and use it to make all the cuts without having to waste time running back and forth.
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