Roof Rafter Joints

The head of the rafter is joint to king post by mortise and tenon joint.

Roof rafter joints.

If you are framing a cathedral ceiling there are a couple ways to deal with the need for rafter ties. 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 joint is further strengthened by a wrought iron strap. The standard size of this rafter is 10 x 15 cm but it varies in using.

Rafters are installed piece by piece during the construction of the roof. The principal rafter is jointed to the tie beam by a bridle joint. 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. Rafters are beams that run from the peak of the roof to the top plate of the supporting walls.

Due to the width. 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. In traditional timber they are nominally 2 inches thick and typically 8 to 10 inches wide.

Each beam is notched at the bottom called a birdsmouth so that it rests flat on top of each wall. A common rafter comprises two beams that extend upwards from the top plate of either side of a shed wall. For example in an equal hip roof with an 8 12 pitch the pitch of the hip rafter would be 8 17. 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.

Keep the framing square in the position that it was set in to measure the birdsmouth cut. Birdsmouth joints cut into roofing rafters and mounted in place on top of the wall plate. But here it will be different since the hip rafter doesn t lie at 45 degrees to the commons. 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.

At the top where the rafters meet they are either angled to meet at a point or attached to a horizontal ridge beam. Possibly the most satisfiying part of the roof yet. Definition of collar tie in roof framing. Rafters form the foundation for attachment of the roof boards onto which the final roof covering is fixed.

Slide the framing square until the 6 in 15 cm mark intersects the line you ve marked for the birdsmouth cut. Unit run of the hip.