Roof Support Birdsmouth

As we have briefly mentioned above the birdsmouth joint is mainly used in forming traditional cut roofs to ensure that the rafters or joists that form the roof sit securely on top of the supporting wall plate.

Roof support birdsmouth.

Measure the distance from the outside of one wall to the outside of the other wall subtract the width of the ridge plate divide by two and multiply that number by itself. A birdsmouth cut involves taking a notch shaped like a bird s mouth out of each rafter where it meets the top plate. This notch allows the beam to rest flush onto the top plate. How to use a framing square to lay out the birds mouth cut on a rafter.

The roof height is the distance from the level of the floor of the attic to the roof ridge. A lot of force is transferred down the length of the rafter and the seat cut on the birdsmouth transfers that force directly to the top plate. With the ripped strip installation there would be no horizontal bearing surface to resist that force. Roof width distance between the points of support of the rafters.

Measure or calculate the height of the roof from the top of the wall to the top of the ridge plate and multiply that number by itself. This article series explains how to use a framing square and in companion articles we give examples just about every possible way to figure out any or all roof stair or other building framing dimensions and measurements including problems such as figuring the roof area width length and roof or stairway slope rise.