Attic Truss Load Rating

If the bottom chord of a roof truss functions as a floor joist such as in an attic room it carries a live load that also varies by use but a typical live floor load for a residential space is about 40 pounds per square foot.

Attic truss load rating.

So if your ceiling is unfinished you have some excess carrying capacity up there. Included are a series of representative roof truss span tables that will give you an idea of the truss spans available for a particular load condition load duration lumber type and truss configuration. Is a safe estimate. The truss is analyzed for each possible location of the 640 plf load along the span.

The shapes and spans shown here represent only a fraction of the millions of designs produced by alpine engineers. If the number of members is labeled m and the number of nodes is labeled n this can be written as m 3 2 n. This truss load table guide illustrates how to read allowable load ratings for aluminum and steel truss. The box truss is 290mm x 290mm 11 42 x 11 42 square.

Keep in mind that these tables are for estimations only. The formula for truss loads states that the number of truss members plus three must equal the twice the number of nodes. Of stuff on it. Or the 25 psf snow load could be entered as a roof snow load with the unbalanced snow loading option turned off.

The horizontal bottom chords of most garage trusses are designed to carry the weight of drywall and insulation. Bcll 0 psf. Both sides of the equation should be equal in order to end up with a stable and secure roof structure. Total load psf duration factor.

Live load psf roof type. Load rating chart ct290 load data ct290 truss sections are manufactured using 50mm 1 97 diameter x 2mm 08 wall main tube and 20mm 79 x 2mm 08 wall diagonal tube 6082 t6 aluminum alloy. If unbalanced snow loading isn t required or specified the truss designer may enter the 25 psf snow load as a top chord live load tcll set the load duration factor to 1 15 for snow and turn snow loading off completely. For trusses at 2 ft o c.

The explanations below will help you determine the appropriate truss to use for your application or conditions based on allowable load ratings. Bcll 0 psf no storage available in floor trusses. Alpine truss designs are engineered to meet specific span configuration and load conditions. Scrap of plywood over the chords and set about 40 lbs.

The live loads a truss is required to bear are determined by local building codes. That means you could lay a 2 x 4 ft.