How To Frame A Gambrel Roof Truss

The truss is a framework consisting of rafters posts and struts which supports your roof.

How to frame a gambrel roof truss.

Calculate gambrel angles with graph paper and a protractor. My bride and i happen to live in a gambrel style. Check overhang to calculate rafter overhang equal to the lower level cut at the full rafter depth. Using a pen trace the inside and outside bends of the trusses on the cardboard making what should look like a double l shape.

Draw a semi circle on the graph paper mark a center peak at the top and draw two lines on each side in the shape desired for the gambrel roof. Our next step is to transfer these measurements to a 2x4 and cut 4 pieces to form our first truss. Then use a saw to cut the lines that you drew. A regular gambrel is one that fits inside a circumscribed semi circle as shown below the shape of the roof is essentially one half of a regular octagon.

With the upper floor sheathed i snapped chalklines for the 2 6 plates on which the trusses would stand. With overhang selected drag slider to increment decrement birdsmouth seat width to suit. Most often gambrel roofs are supported by one piece clearspan gambrel trusses. Transfer measurements to 2x4 s.

Usually you can expect a room from 1 3 to building width with smaller span trusses generally 24 30 foot spans. This step is no different than if i were framing walls. Or 24 o c you want to use. Largest downside to this type of truss system is lack of bonus room width.

Lay out trusses full size on the floor. The slopes for a regular gambrel roof are fixed at 28 31 32 over 12 for the lower rafters and 4 31 32 over 12 for the upper rafters these slopes are rounded to 29 12 and 5 12 for display. Take the number under the column of the center spacing 16 o c. The important point to keep in mind when you use your truss calculator is that every truss calculation is completely unique and is based on the size of your roof and its specific dimensions.

Next lay four of the cut boards on top of the cardboard in the manner in which they will be assembled. Trace the top of the joint so the angle is at the same degrees as where the rafters connect. Gambrel roof framing geometry calculator inch this gambrel roof fits in a semicircle and starts as the top half of an equal sided octagon. Move slider or directly enter angle to alter sweep angle of lower rafters and change the shape.

These pieces are known as the gussets. Sort of like this. Use the protractor to measure those angles at the peak the walls and the point where the two lines intersect on the top side of the roof. Be aware that gambrel trusses may require an architect s or structural engineer s stamp of approval.

Find three pieces of cardboard and lay them on the ground. 4 identical truss pieces for your gambrel shed roof. That truss count number less 1 times 6 count 1 6 total is the number of osb web pieces you ll need to cut.