Bird's mouth cut
A birdsmouth or bird's mouth cut is a carpentry or timber roofing term for a small triangular cutout from a beam either at the end or along one side. It is made up of two cuts to remove a triangular piece of timber, the cuts are at 90 degrees to one another but their angle to the edge of the timber being cut will vary depending on the angle of the roof.
Birdsmouths are cut in to roofing rafters at the top to hang onto and be fixed to the ridge beam as well as lower don the rafter on one side to hang over the edge of the wall plate, making the top of the wall frame or lying on top of the wall if masonry of brick. The combination of the two cuts allows the rafter to sit at an angle to the horizontal beams creating the roof pitch.
[edit] Related articles on Designing Buildings
- Beam bridges.
- Beam formwork.
- Bond beam.
- Cantilever.
- Capping beam.
- Chilled beam.
- Collar beam.
- Flitch beam.
- Girder.
- Ground beam.
- Lattice beam.
- Metal web joists.
- Open web beam.
- Post.
- Rafter.
- Rolled steel joist (RSJ).
- Simply supported.
- Timber post and beam construction.
- Types of beams.
- Types of columns.
Featured articles and news
Shading for housing, a design guide
A look back at embedding a new culture of shading.
The Architectural Technology Awards
The AT Awards 2025 are open for entries!
ECA Blueprint for Electrification
The 'mosaic of interconnected challenges' and how to deliver the UK’s Transition to Clean Power.
Grenfell Tower Principal Contractor Award notice
Tower repair and maintenance contractor announced as demolition contractor.
Passivhaus social homes benefit from heat pump service
Sixteen new homes designed and built to achieve Passivhaus constructed in Dumfries & Galloway.
CABE Publishes Results of 2025 Building Control Survey
Concern over lack of understanding of how roles have changed since the introduction of the BSA 2022.
British Architectural Sculpture 1851-1951
A rich heritage of decorative and figurative sculpture. Book review.
A programme to tackle the lack of diversity.
Independent Building Control review panel
Five members of the newly established, Grenfell Tower Inquiry recommended, panel appointed.
Welsh Recharging Electrical Skills Charter progresses
ECA progressing on the ‘asks’ of the Recharging Electrical Skills Charter at the Senedd in Wales.
A brief history from 1890s to 2020s.
CIOB and CORBON combine forces
To elevate professional standards in Nigeria’s construction industry.
Amendment to the GB Energy Bill welcomed by ECA
Move prevents nationally-owned energy company from investing in solar panels produced by modern slavery.
Gregor Harvie argues that AI is state-sanctioned theft of IP.
Experimental AI housing target help for councils
Experimental AI could help councils meet housing targets by digitising records.
BSRIA Occupant Wellbeing survey BOW
Occupant satisfaction and wellbeing tool inc. physical environment, indoor facilities, functionality and accessibility.