Meaning of birdsmouth | Babel Free

Definitions

A notch cut into the underside of a rafter to ensure that it does not move when resting on the wall plate running across the top of a wall; a similar notch in other timber components.

Examples

“Support⟳ the veneer stack on a ¾-in.-thick board⟳ with a narrow V notch cut⟳ into one edge. This board⟳ is called a birds-mouth, and the V notch provides clearance for the blade while the work⟳ is supported for cutting.”

“After the wall and ceiling framing has been completed the erection of the roof takes place⟳. Nail the four straight rafters selected as the first and last⟳ into position at the birdsmouth.”

“birdsmouth, sally; in timber frame construction, a notch cut⟳ into the end⟳ of an inclined timber to receive⟳ a horizontal timber running perpendicular to it; used for the housing of rafters; other similar notches in other components: birdsmouth brick a special brick manufactured with an indented end⟳, designed for use⟳ in decorative brickwork and at an internal obtuse corner in a brick wall. […] birdsmouth joint, birdsmouthed notched joint; in timber roof construction, a joint formed by notching the extremity of a rafter with a birdsmouth and fastening it to a wall plate; any joint similar to this.”

“There are various ways of tying rafters to sidewalls, and the choices may vary⟳ depending on roof pitch. One of the most common is the use⟳ of “birdsmouths” cut⟳ into the rafter. A notch is cut⟳ into the rafter so that the rafter bears down flat upon the doubled top plate of stick⟳ framing, or upon the girt in heavy timber framing.”

“A birdsmouth is a notch cut⟳ into the underside of a roof rafter to enable it to sit⟳ tightly and securely on the timber wallplate that runs across the top of a wall. It's so called because it resembles the wide-open mouth of a baby bird wanting to be fed.”

CEFR level