Roof Rafter Joints

Measure the rafter overhang.

Roof rafter joints.

Each beam is notched at the bottom called a birdsmouth so that it rests flat on top of each wall. The standard size of this rafter is 10 x 15 cm but it varies in using. But here it will be different since the hip rafter doesn t lie at 45 degrees to the commons. At the top where the rafters meet they are either angled to meet at a point or attached to a horizontal ridge beam.

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. The head of the rafter is joint to king post by mortise and tenon joint. Birdsmouth joints cut into roofing rafters and mounted in place on top of the wall plate.

Rafters form the foundation for attachment of the roof boards onto which the final roof covering is fixed. In traditional timber they are nominally 2 inches thick and typically 8 to 10 inches wide. By upper third here we mean one third of the length of the rafter from ridge to top plate. The principal rafter is jointed to the tie beam by a bridle joint.

Rafters are installed piece by piece during the construction of the roof. If you are framing a cathedral ceiling there are a couple ways to deal with the need for rafter ties. 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. For example in an equal hip roof with an 8 12 pitch the pitch of the hip rafter would be 8 17.

Unit run of the hip. If for example you want the rafter to overhang the edge of your building by 6 inches 15 cm measure this now. 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. 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.

Due to the width. Slide the framing square until the 6 in 15 cm mark intersects the line you ve marked for the birdsmouth cut. The joint is further strengthened by a wrought iron strap. Possibly the most satisfiying part of the roof yet.

Definition of collar tie in roof framing. Rafters are beams that run from the peak of the roof to the top plate of the supporting walls.