Comprised of prefabricated lightweight wood, trusses are made most commonly made from 2x4 or 2x6 beams but can sometimes be as large as 2x8.
“A 2×6 spaced 16 inches apart can span a maximum distance of 13 feet 5 inches when used as a rafter, 10 feet 9 inches when used as a joist, and 6 feet 11 inches when used as a deck beam to support joists with a 6-foot span.”
2x4 are pretty standard for roof trusses. 2x6 or bigger is for heavier snow loads and or longer spans between webbing.
Rafter boards that create the slope of the roof are typically wider than ones used to create trusses. While 2x4s are most common in trusses, 2x8s, 2x10s, and 2x12s are most common in rafters. In a finished space, insulation is placed between the rafter boards and drywall.
If you are building on a concrete pad then 4 x 2 tantalised would be fine. For the roof, because the roof doesn't take any real weight, 4 x 2 over a 3 metre span should be fine. The weight of the OSB boards would be evenly spread so would not cause any problems with sag.
2x4 11'-6" 2x6 17'-0" 2x8 21'-8" 2x10 25'-7" 24" O.C.
The recommended thickness of ⅝” provides sufficient strength and prevents bowing between framing. It's important to note that the minimum thickness requirement is 3/8 inch. Factors such as plywood, oriented strand board (OSB), wood boards, concrete, and exterior gypsum board can influence the sheathing thickness.
There are several reasons: Roof trusses are built in volume, allowing truss manufacturers to take advantage of bulk discounts on raw materials. Contractors often cannot access these types of discounts, making it more cost-effective to buy pre-made trusses. Roof trusses save time in labor.
Law of Statics of Trusses
The law of statics shows that trusses, when loaded along two points, will result in axial forces (forces acting along the axis) that are equal in size and face opposite directions. If trusses are loaded by downward forces, the components at the top are in tension.
The span across the truss from end to end is about 28', with no bearing wall or support at midspan.
There is almost no difference in the bearing capacity — the wall's ability to support a compressive load, which is how most walls are loaded.
Roof trusses are more wallet-friendly, coming in at $5 to $14 per square foot, installed, while roof rafters are $7 to $30 per square foot, installed.
Trusses are made most commonly from 2x4 or 2x6 beams but can sometimes be wider dimensional boards as large as 2x8. The truss system allows for greater durability and load bearing.
The 2×6 joists will sag, no doubt, says DanH. “They will probably not collapse, and the load will probably not compromise the structure.
Truss count = ((roof length * 12) / 24) + 1
The simplest form of this equation is to take the length of your roof and divide it by 2. For example, if your roof is 40-feet long, it will need a total of 20 trusses.
Utility-grade studs shall not be spaced more than 16 inches on center or support more than a roof and ceiling, or exceed 8 feet in height for exterior walls and load-bearing walls or 10 feet for interior nonload-bearing walls.
Every truss requires at least two bearings, or points, to transfer its loads to. Typically, it is a 2x4 or 2x6 wood frame wall or panel in residential construction but can also be a light gauge steel wall or block wall in commercial or industrial applications.
A good rule of thumb for truss spacing is to divide the length of the roof by two; this gives you an estimate of how many trusses you will need. However, ensuring accuracy in your measurements involves more than simply guessing.
In short, the answer is yes, you can build your own truss. But while it's possible, keep in mind that only building engineers can ensure accurate results.
Installation challenges: Roof trusses can be difficult to install in areas with limited access or where there are obstacles that prevent them from being installed in one piece. Less repairability: Roof trusses are difficult to repair if they become damaged. They may need to be replaced entirely, which can be expensive.
Due to their triangular structure, scissor trusses are highly durable. They can be the sole roof support in larger spaces, often eliminating the need to combine them with other types of trusses.
In terms of resistance to moisture, plywood has the edge. While OSB takes longer to become saturated when wet, it also takes significantly longer to dry. OSB also swells more when it comes in contact with water, especially at the edges.
Typically, half-inch plywood or ¾ inch plywood is the best for roof sheathing. This provides a solid foundation for your shingles while not overloading the decking with heavy wood.
Cedar is one of the most popular choices for building wood roofs—and for many reasons. First, it's one of the most beautiful types of wood. It typically has a lighter color to it while also carrying a deep enough color to provide a rustic vibe.