To design a gambrel roof, calculate how many tresses the structure needs by accounting for one truss for every 16 inches, and then determine the height of the roof based on a top angle of 30 degrees and side angles of 60 degrees. Sketch out the intended design before cutting and assembling the trusses.
Gambrel roofs feature trusses with a double bend, which allows for greater usable height than simple pitched roofs. To design and construct a gambrel roof:
- Calculate the trusses
- Determine the angles
- Mark and cut the lumber
- Assemble the pieces
- Reinforce the trusses
Trusses are typically placed every 16 inches on center, with a truss placed on the front and back of the building. Measure the length of the building and determine how many trusses are needed.
Designs can vary, but the trusses typically feature a top angle of 30 degrees with the two side angles measuring 60 degrees. Determine how tall the trusses will be based on the desired angles.
Cut and build the trusses on the ground before attaching them to the building. Use 2-by-6-inch lumber and a chalk line to mark the areas that need to be cut. Use a circular saw to cut the boards, and use the first board as a template for the remaining boards. Cut plywood to create the plywood brackets that connect the angled pieces together.
Lay the cut pieces on the ground and join the sides together by nailing the brackets onto the side pieces.
Use 2-by-6-inch boards to create reinforcement pieces that match the side angles of the trusses. Nail these pieces onto the bends to reinforce the brackets.