Attic Truss Bottom Chord Live Load

The remaining portions of the joists or truss bottom chords shall be designed for a uniformly distributed concurrent live load of not less than 10 lb ft2 note that in footnote b the uninhabitable attics without storage have a 10 psf non concurrent live load while this same load in footnote g i e.

Attic truss bottom chord live load.

In other words the truss design drawing should tell you what the truss was designed for. I for sloping or flat roof with slopes up to and including 10 degrees. A when access is provided 1500 n m 2 b when access is not provided 750 n m 2 except for maintenance ii sloping roof with slope greater than 10 degrees. 20 4 10 means that the truss was designed for 20 psf top chord live load tcll 4 psf top chord dead load tcdl 0 psf bottom chord live load bcll and 10 psf bottom chord dead load bcdl.

If the number next to bcdl bottom chord dead load is less than five psf pounds per square foot then the trusses and the building are not designed to support a ceiling. The load on the outside of the roof. In floor truss applications 2x4 or 2x3 material is typically used with the wider portion of the board resting on the bearing or what is known as a 4x2 configuration. The area of the attic where storage loads are not applied is listed as a concurrent 10 psf live load.

Live loads on roof trusses. Every truss design drawing must specify the loads that have been accounted for in the design. The truss shown below is known as an attic truss or a room in attic truss. An example of this is a vaulted ceiling application framed by scissors trusses.

This type of truss carries a combination of roof l r or s and floor l loading in addition to the standard top and bottom chord dead loads. The live loads a truss is required to bear are determined by local building codes. The live load shall be taken as follows. Mike truss guy guest re.

Lately many have also been designing for an alternate load of 20 psf in the rectangle mentioned in the previous post. A the top chord and bottom chord dead load. Trusses w storage on the lower chord most trusses will handle 10 psf live load anywhere in the attic non concurrent with other live loads i e. On the truss drawing will be a section which outlines all of the live and dead loads which the trusses are designed to support.

In some cases a live load can be applied to a bottom chord either for storage purposes or if there will be movement within the truss such is the case in an attic truss.