Graphical Construction Glossary >> Woodwork. >> Joints >> Birdsmouth Joint

Birdsmouth Joint
A joint at the base of an angled member that is designed to stop it sliding.

a birdsmouth joint

Best known in roofing as the joint between rafter and wall plates the humble birdsmouth joint is used a lot for permanent propping of under purlins in roofs and for temporary propping in formwork and shoring work.

The sketch above shows the centre lines of the two members lining up, and this works in most cases. It is a good rule of thumb that makes sure that the small lip is never so small that it can split off under load and let the prop slide. Usually fixed with nails in temporary work.

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Please Note! The information on this site is offered as a guide only!  When we are talking about areas where building regulations or safety regulations could exist,the information here could be wrong for your area.  It could be out of date!  Regulations breed faster than rabbits!
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