Gambrel roofs are the traditional "barn" style design. They provide more space in the upper part of a building than a gable or hip roof, whose sides tend to slant more steeply. A gambrel roof has a peak with a mild pitch, then one or more slopes of increasingly sharp angles. This type of roof is attractive, offers good protection from rain and snow, but is more difficult to build than a standard gable roof because of the varying angles. Some gambrel roofs have only two pitches -- some may have as many as four.
Things You'll Need
- Roof design book
- Roof angle calculator (optional)
- Graph paper
Determine the dimensions of your shed. Decide how much interior room you need. Decide how much head room space you want at the center and the sides. Look at gambrel roofs of other buildings, houses, barns and structures as well as sheds. Choose a style that is visually appealing and efficient for your needs. Some gambrel roofs have a modest slope from the peak about a third of the way down the roof, then a sharper drop to the edge. Others have very little slope for a short span, then a slightly steeper pitch, then a final pitch almost vertical.
Compare gambrel framing techniques. Traditional gambrel roofs use rafters with varying angles, connected by diagonal braces between rafters. Most backyard sheds have a two or three rafter system, connected by a horizontal ridge board running from one end of the shed to the other, and braced with cross members between the rafters. These are assembled on the ground and lifted into place atop the shed walls. Depending on the size, you may need one or more helpers to do this.
Use gusset bracing to simplify construction of the rafter and brace framing for the roof. The rafters are still cut to form the different pitches, but the joints are connected with gussets rather than angled braces. Gussets are straps or plates made from wood or metal, and secure the frame pieces together. During construction, a gusset is nailed to two frame pieces where they meet at a joint. This makes the completed gambrel rafter somewhat resemble a "hinged" arch. Gusseted rafters are easier to build and just as strong as conventional braced rafters. They are especially useful on a shed.