You’ll need steel strapping and brackets, too. Therefore, if you live in a zone that experiences 140 mph wind uplift and you space your trusses at 24 inches, you’ll have to reinforce the truss-to-wall connections with something more than nails. The further apart you space your trusses, the greater the need to anchor them more securely to the walls becomes. This may alter how you space your roof trusses. If so, you’ll have to check a wind uplift forces chart. Typically, this would be anywhere than experiences hurricanes. The first is to understand if you are in a zone that experiences extremely high winds. When it comes time to plan your roof truss spacing, there are a few things you need to keep in mind. This allows for easy placement of sheathing above and drywall below while still providing the adequate strength necessary to support all live loads a roof is meant to handle. However, you’ll need several more trusses at that spacing, negating your savings.įor these reasons, most builders opt to place trusses at 24”. A truss designed for 16” centers will probably use a slightly lower grade of wood, resulting in a slightly lower cost per lineal foot. How much less? It depends on the slope of the roof and the span of the truss. Naturally, a truss designed to sit at 16 inches spacing will have less wood than 24” on center. A question they’ll eventually ask is for spacing – how far apart do you plan on spacing your trusses? Once you’ve answered that question, then the trusses will be designed to fit the span and spacing. When you build a house or a contractor is building a roof, you’ll have to order your roof trusses from a building materials supplier. Will a roof be subject to failure with trusses spaced at 24” rather than, say, 16” on center? Not at all, and it all has to do with how trusses are made. The reason for this is solely to do with cost – it is cheaper to space at 24 inches as you need fewer trusses. If you were to take the roof off of most of the homes in your neighborhood with trusses, you’d more than likely find that nearly all of them are spaced at 24” on center. As there are up to 10 grades of wood for some common dimensional lumber species, a truss needing reinforcement may get premium wood versus another that gets a #2 grade. The added lumber will also increase the cost of that truss.įinally, truss manufacturers will make roof trusses with a higher grade of wood for trusses spaced further apart or need to bear heavier loads. This will nominally increase the price of that truss per linear foot.Īlternatively, reinforcing a truss might also mean adding a couple of extra truss webs between the openings of a truss. A gable truss that needs reinforcement to adapt to a greater spacing, such as 24”, may have the bottom chord – a 2×4 – replaced with a 2×6. Take a standard gable truss design, for instance. How can trusses be fabricated to fit the same spacing? Trusses can be made to use more wood, a larger dimension of wood, or a higher grade of wood to provide a greater truss spacing. Luckily, all trusses can be designed to fit the same spacing, making it much simpler for builders when it comes time to build a structure. All have different load and span requirements, and therefore have different requirements for spacing them. There are hundreds of different types of roof trusses. They are also pre-designed by an engineer, whereas rafters require the builder to consult span charts and decide upon the proper spacing and lumber dimensions. One reason builders prefer trusses is that they come to the job site preassembled, so all you have to do is attach them to the walls – much quicker. Rafters are often more expensive because the lumber used is wider. They attach to a ridge beam at the top and the wall framing below. Roof trusses differ from rafters in that rafters use dimensional lumber – usually 2圆s or 2x8s – for their main framing members – the rafters. The important thing to remember is that no matter what type of truss design you use, they are always pre-fabricated before the job. For every type of roof, there is a truss designed to support it. Some can accommodate raised ceilings below, such as a scissor truss, while others, such as a parallel truss design, are used for flat roofs. There are many different styles of a truss. They are usually a series of 2×4 or 2×3 pieces of lumber connected via “webs” to support the roof sheathing and support any type of roof load, such as snow.
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