Raised Tie Truss: How to Build a Roof System

The Working Definition of Raised Tie Truss

A raised tie truss is a roof system that utilizes rafters, purlins and ridge boards. Rafters are the vertical members of the frame that span from wall to wall in order to support the weight of the roofing material. They have an inverted V shaped cross section called a “bird’s mouth” at their end where they attach to adjacent rafters or supports. Purlins are horizontal members that lie perpendicular to the rafters and help distribute load across more than one rafter. Ridge boards are structural components used at either end of a roof structure for support like purlins but only on one side of each end rather than both sides as with purlin connections.

Raised Tie Truss

A raised tie truss is a roof system that utilizes rafters, purlins and ridge boards. Rafters are the vertical members of the frame that span from wall to wall in order to support the weight of the roofing material. They have an inverted V shaped cross section called a “bird’s mouth” at their end where they attach to adjacent rafter or supports. Purlins are horizontal members that lie perpendicular to the rafters and help distribute load across more than one rafter. Ridge boards are structural components used at either end of a roof structure for supports like purlin connections but only on one side each end rather than both sides as with purlin connections.

The primary difference between a conventional framed building and this type lies in the roof. Instead of a conventional framed building, where the rafters are spaced close together and then covered with plywood sheathing or another material such as asphalt shingles to form the roof surface, in this type the rafters are spaced farther apart; they support purlins that span between them.