Roof Rafter Joints

A common rafter comprises two beams that extend upwards from the top plate of either side of a shed wall.

Roof rafter joints.

If you are framing a cathedral ceiling there are a couple ways to deal with the need for rafter ties. Rafters form the foundation for attachment of the roof boards onto which the final roof covering is fixed. If for example you want the rafter to overhang the edge of your building by 6 inches 15 cm measure this now. By upper third here we mean one third of the length of the rafter from ridge to top plate.

Possibly the most satisfiying part of the roof yet. In traditional timber they are nominally 2 inches thick and typically 8 to 10 inches wide. Unit run of the hip. In a hip roof with equal pitches the unit run of a hip or valley rafter is 17 inches for every 12 inches of run in the main roof.

Birdsmouth joints cut into roofing rafters and mounted in place on top of the wall plate. The head of the rafter is joint to king post by mortise and tenon joint. Keep the framing square in the position that it was set in to measure the birdsmouth cut. Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure.

For example in an equal hip roof with an 8 12 pitch the pitch of the hip rafter would be 8 17. Rafters are installed piece by piece during the construction of the roof. Rafters are beams that run from the peak of the roof to the top plate of the supporting walls. Slide the framing square until the 6 in 15 cm mark intersects the line you ve marked for the birdsmouth cut.

Definition of collar tie in roof framing. A collar tie is a horizontal roof rafter compression connector that is located in the uppermost third of the span of a pair of opposed sloped or gable roof rafters. If is wasn t for this joint a rafter or roofing joist would only balance on top of the wall plate making fixing difficult not to mention the fact that there wouldn t be any solid connection between the roof and the supporting walls below. Rafter ties or ceiling joists acting as rafter ties are required by code unless the house is designed so that the walls or a structural ridge beam carries the full load of the roof.

The standard size of this rafter is 10 x 15 cm but it varies in using. Measure the rafter overhang. But here it will be different since the hip rafter doesn t lie at 45 degrees to the commons. Each beam is notched at the bottom called a birdsmouth so that it rests flat on top of each wall.

They join at the peak of the roof by connecting to the opposing rafter or to a ridge beam that runs the length of the peak of the house or shed. The joint is further strengthened by a wrought iron strap.