Q&A for How to Build a Simple Wood Truss

Assuming a gable roof -- 1/2 of 28' = 14'. A pitch of 3/12 means a rise of 3" for every 12" of run so 3 x 14 = 42". WARNING: this is a very low pitched roof. In many places the building codes won't allow it (especially in northern climates).

It will depend on the pitch of the roof and the length of the overhang. Provide more information so it can be answered accurately.

Best place is to go to your local hardware store/lumber yard.

9 for a simple structure. Divide 16' by 2' and add a truss for the last gable truss. Note that the gable trusses are often times configured differently.

Yes. 2x4s are commonly used to build trusses for smaller structures like carports, detached garages, and sheds.

The bottom chord of the truss will need to be the same length as the floor of the shed, plus 0.25 inches to ensure a proper fit. The exact height of the truss will depend on the height of the roof. If you're adding a truss to a flat roof, you'll have some control over what slope you want.

This depends on the style of building. On residential structures, 2' is usually the minimum required. On a pole shed or timber frame it could be 4' or as much as 9' for a pole shed.

It depends on how you are laying out the trusses. The answer is either 6 or 7, assuming a truss spacing of two feet on center. 10'/2'+1=6 or 12'/2'+1=7

Normally, one would put trusses every two feet. Then put on 4'x8' sheets to deck it with. So, with yours, it'd be 3600 of them.

For a sturdy roof, four should be fine. Install one at every end and 24 inches on center for the other two.

45 degrees is considered standard according to most building codes. If you go any steeper, you may need special fasteners and/or equipment to be able to walk on the roof safely.

Yes, but may require a different configuration of the bracing, depending on where the wall is placed.

If you are using pole barn construction and 2 x 10 or 2 x 12 lumber you would be able to use fewer purlins. Otherwise your structure would not be sound and could fall over.

Assuming 15 m is your length, convert 15 m to feet, which gives you 49.2 ft. Round it up to 50 ft and then divide by 2, which gives you 25 trusses plus one for the last edge/ending. In total, you need 26 trusses spaced every 22 1/2 inches to make the distance even between each truss.

Yes. 4-12 pitch is fairly standard. It is not recommended to go less than 4-12.

It depends on the span you are covering and what spacing you want. For 2' truss spacing, for example, take the length of your building, divide by 2, then add 1.

A 2x3 would be ample; any bigger than that size would be a waste of cash. Work out the length you are using for your build type. Always have it just that bit bigger than you think it should be or that you calculated.

That is dictated by the rise/run of the truss itself. The king post is cut into a point, with that point's angles matching the angle degrees the top chord is. In a 12/12 truss, the angle at the top is 90º. The king post would be cut 45/45 to make a 90º point on top. The more shallow the truss rise, the more shallow the angles on the king post.

No, there is no structural need for an overhang. Overhangs are two things: decorative, and water management. Some older homes have no overhangs or eaves on gables. So, you design your truss chords to meet over the wall, or what's called a cantilever. A cantilever extends the chords outside the but is braced to withstand load. The length depends on the total width of the house. Also, there are designs that are considered energy efficient by building in a small cantilever, and a vertical support over the wall, so at that point, you can have deep insulation. In a normal design, the insulation over the wall is only as high as the vertical thickness of the top chord.