That means you could lay a 2 x 4 ft.
Roof trusses weight load.
This means a 30 foot span is 50 wider than a 20 foot span but must have 225 of the load carrying capacity.
The load carrying capacity is handled by larger or higher graded material being used for the truss top and bottom chords as well as the webs.
Safe load per table 4 1 specifies a 2000 lb over a 2 5ft x 2 5ft area.
Bcll 0 psf.
This translates into a uniform load of 640 plf across 2 5 ft of the span.
For trusses at 2 ft o c.
Of stuff on it.
Bcll 0 psf no storage available in floor trusses.
If you have another floor above your garage the ceiling floor structure can usually support up to 40 lbs sqft including the weight of the floor above it.
In engineering calculations the span of a beam a truss is a beam is squared.
The horizontal bottom chords of most garage trusses are designed to carry the weight of drywall and insulation.
The formula for truss loads states that the number of truss members plus three must equal the twice the number of nodes.
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.
When it comes to estimating the weight of an existing roof field verification of the in place construction is necessary.
If you do not have another floor above the ceiling trusses may only be able to hang a maximum of 10 lbs sqft.
The truss is analyzed for each possible location of the 640 plf load along the span.
Is a safe estimate.
This includes the roof deck and the supporting structure typically roof trusses and or rafters as well as the roof system itself.
The live loads a truss is required to bear are determined by local building codes.
So if your ceiling is unfinished you have some excess carrying capacity up there.