Birds Mouth

What does Birds Mouth Mean?

Definition of Birds mouth in Construction
Term used to identify the end of a rafter where it sits on the plate of the structures exterior wall. The term birds mouth is used, due to the rafter’s appearance, similar to a bird’s mouth. The rafter must be cut to sit evenly on the top of the horizontal plate and extend beyond the perimeter of the structure to form an overhang or soffit cantilevered off the side of the structure. The cutting of a proper bird’s mouth requires an experienced carpenter that knows how to maneuver a framing square. In most cases, once the birds mouth has been measured and identified, one is cut to ensure accuracy. Once this pattern rafter is cut, all the other rafters for the project are cut to match this patterned rafter. Both the ridge cut and the birds mouth are cut the same on all the rafters. In this manner the structure when finish framed will be consistent throughout the roof line.