How to Build a Gambrel Roof

Learn the design and construction of a gambrel roof for a house.

| March/April 1977

A couple years ago, when I was building my 15-by-20 foot log cabin in far northern Washington, I decided to top the building with a gambrel (rather than a more conventional gable or A-frame) roof. Not only would the gambrel's steep side pitch give the cabin ample upstairs room, I reasoned, but the double-sloping design would make more efficient use of roofing materials than a giant A frame ever could. And besides that, I like the looks of gambrel roofs.

Some background reading soon taught me, however, that a conventional barn-sized gambrel is a nightmare of purlin beams, ridge beams and dovetail joints. What I had in mind, in other words, was a fine project for an army of engineers, but one that was probably beyond the capabilities of two non-professionals (such as Jim — my building partner — and myself).

Rather than give up, however, I decided to try to simplify the construction of the gambrel I wanted. What I ultimately devised was an easy-to-work-with system of lightweight trusses that could be built flat on the ground, then erected atop the cabin and covered with exterior plywood. Here, briefly, is how the trusses (and the gambrel roof formed from them) went together:

Research and Planning

I'd planned to start by making a dozen or so gambrel-shaped frames or trusses out of 2-by-6 lumber. Initially, though, I had no idea how I could connect the pieces of each truss together so that they'd be held rigidly in the proper configuration.

Then I remembered reading about a system of plywood straps that someone had used in building a geodesic dome. I say "straps" but, actually, they were nothing more than wooden brackets nailed to the sides of two connecting beams to hold them (the beams) together. These plywood brackets were just what Jim and I needed to give our roofing trusses adequate rigidity.

Next we sat down and made scale drawings of several gambrel roof designs, each one employing a different combination of side slopes. In the end, we settled on a roof plan that looked good, made efficient use of materials, and allowed for porch and eave overhangs.

3/28/2014 1:01:38 AM

Gambrel roofs are a great way to add square footage to homes. Homes in College Station roofing are mostly traditional, sloped, shingle roofs. However, as home values rise, many residents are looking for ways to capture equity in a growing market. Adding a small loft, bedroom, or study is a great way to add extra floor space. Increasing square footage will directly increase property value.

Rob Roath
1/5/2012 5:05:57 AM

Wow found this while surfing around. Pretty cool deal.

9/6/2007 9:45:24 AM

I enjoyed your article on gambrel roofs. I am thinking of building a 16-20 shed with a gambrel roof and the article helps. However you refer to figures 1 and 2 a,b,c. I can't find any diagrams with the article, am I missing something? Mother Replies: The illustrations are in the Image Gallery at the top right of the article.

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