How to Build Gambrel Roof Trusses
Gambrel roof trusses are a popular style used often in barn or garage construction. The double bend in the trusses makes for a more spacious area that affords more usable square footage than the average roof truss. Because of the number of bends in these trusses, each one is custom made to specifically fit the roof that it will be installed within. For this reason, these trusses are usually constructed at the job site rather than premade. Here are seven easy steps that explain how to do it yourself.
Step 1 – Determine How Many Trusses Will Be Needed
Using the size of the building as a guide, determine how many trusses will be needed for the roof. There should be one truss at each end and the rest should be placed every 16 inches on center.
Step 2 – Decide How Tall the Roof Should Be
The trusses can be any height, but the typical angle of the upper section of a gambrel truss is 30 degrees and the typical angle of the lower section generally has a bend of 60 degrees.
Step 3 – Layout the Material for the Trusses
Using 2x6 lumber, begin preparing the trusses by laying out four of the boards on a flat space of ground. Using a protractor, adjust the boards on top of one another so that they create the angles needed for the trusses (which, as stated above, are usually 30 degrees on the top section and 60 on the bottom). Stakes should be driven into the ground on either side of the boards to hold them in place. Once secure, use a chalk-line to mark the angles that need to be cut.
Step 4 – Cut the Boards
A circular saw can be used to cut both the length of the boards and the angles of the trusses so that they fit the shape and size of the roof. Once the first four boards are cut, they can be used as a template to make the rest of the trusses.
Step 5 – Cut Plywood for Brackets
Find three pieces of cardboard and lay them on the ground. Next, lay four of the cut boards on top of the cardboard in the manner in which they will be assembled. Using a pen, trace the inside and outside bends of the trusses on the cardboard, making what should look like a double “L” shape. Use a separate piece of cardboard for the upper bend and the lower bend. Then, lay the third piece of cardboard where the two sides of the truss will meet at the peak of the roof and trace just the inside angle. Square this tracing off to make it look like a large triangle shape. When finished, cut out the shapes on the cardboard and apply them to sheets of plywood that are half an inch thick. Trace around the cardboard shapes to make templates of truss support brackets. Once traced onto the plywood, cut the shapes out with your circular saw.
Step 6 – Assemble the Trusses
Place the cut 2x6 boards back between the stakes that were pounded in the ground, once again keeping them in place. Attach the L-shaped pieces of plywood to the sides of the trusses with eight-penny nails. The brackets should follow the bend closely and be applied to both of the opposite sides of the angles. Next, attach the triangle brackets to the top of the truss to join the two sides.
Step 7 – Reinforce the Side Support Brackets
Finally, miter cut short 2x6 boards so that their ends match the same angles as the side angles of the truss. Make enough so that there will one for each bend in the trusses and secure them to the trusses with eight-penny nails for reinforcement.
And with that, your trusses are finished and ready for you to continue with construction.