The Building Designer providing accurate wall or beam/header information in the Construction Documents is essential in order for the Truss Designer to arrive at the correct bearing width.
There are two key bearing related considerations—bearing capacity of the truss and bearing capacity of what the truss is sitting on; often, the bearing capacity of this material is an unknown and an assumption must be made.
The options for dealing with insufficient bearing need to be considered and specifically dealt with on a case-by-case basis.
The strength axis of a structural panel is the direction parallel to the grain of the wood fiber in the face and back surfaces of the panel.
The strength axis is usually the long dimension of the panel.
The IBC provides two tables with the allowable spans and loads (psf) for wood structural panel sheathing installed continuous over two or more spans with their strength axis perpendicular and parallel to the supports.
There is often confusion in the marketplace about what criteria must be met to accept a new product and approve it for use in the intended application.
The IBC and IRC require products not approved within the code to be “at least the equivalent of that prescribed in this code in quality, strength, effectiveness, fire resistance, durability and safety.”
Manufacturers of products that do not have span tables or design values listed inside the IRC and/or IBC must provide design values for their products through independent testing.