Roof Truss Load Path

Design loads the building dead load is the only known load.

Roof truss load path.

Truss spanning between bearing walls. Vertical load path in traditional sloped roof framing loads are transmitted vertically downward through the roof framing to the exterior walls that transmit the load downward to the home s. 910 pounds per lineal foot. 50 psf x 14ft 700 pounds per lineal foot.

The building is designed for design load possibilities that may never occur. The sheathing transfers the loads to the roof rafters. All other forces will vary in magnitude duration and location. It is important to list live load dead load and total load separately because live load is used to compute stiffness and total load is used to calculate strength.

A primary goal for buildings subjected to high winds is to maintain a continuous load path from the roof to the foundation. Total load psf duration factor live load psf roof type 55 1 15 40 snow shingle 55 1 15 30 snow tile 47 30 snow 40 20 snow 1 25 20 construction or rain not snow load 55 1 15 40 snow 47 1 15 30 snow 40 1 15 20 snow 40 1 25 20 rain or constn. This allows wind uplift forces on the roof to be safely distributed through the walls to the foundation. 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.

All roof and wall loads are assumed to be uniform with no concentrated loads on the trusses or walls present. The live load shall be taken as follows. I for sloping or flat roof with slopes up to and including 10 degrees. The irc does not provide specific guidance as to when blocking may be required to transfer the loads directly.

The truss could be designed based on the assumption that the 25 psf roof snow load is a factored ground snow load in which case a ground snow load is back calculated using asce 7 based on the specified roof snow load pg 25 psf therein lies the problem with specifying only a roof snow load. The roof rafters transfer the loads to the ceiling joists and to the bearing walls that support the trusses. Load path loads on the roof are initially supported by the sheathing. Roof truss span tables alpine engineered products 15.

Per ansi tpi 1 2014 section 7 5 2 1 figure 4 all loads being applied from roof trusses to wall and wall to ribbon board are considered to be applied as uniform plf loads. 15 psf x 14ft 210 pounds per lineal foot. Live loads on roof trusses.