If you intend to to use prefabricated roof trusses, Standard Homes recommends that you order the roof truss option along with your plans. Although the truss manufacturer will provide all truss designs and a plan layout of the roof system, they do not usually redesign the foundation plan for the house. Since roof trusses transfer roof and ceiling loads to exterior walls, they eliminate the need for interior load bearing walls. Accordingly, the foundation and floor framing system in the roof truss version reflect the absence of these interior bearing walls. Fewer piers are required to support the floor, and floor joist spans can be adjusted to better accommodate standard lumber lengths. The roof truss version of a plan outlines the general specifications for the roof system, which the truss manufacturer will use to determine the design and location of the trusses.
In contrast, a stick-built roof system must have interior load bearing walls, so more piers are needed in the foundation to support both the ceiling and floor framing. If you order a plan with a stick-built roof and ceiling system but decide to build with roof trusses, your foundation may be over-designed and may cost more to build.