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Carpentry & Joinery

birdsmouth dimensions

Anonymous user 23/02/2024 - 2.55 PM

i am building a pitch roof with 4x2 timber what would the dimensions of the birdsmouth pls

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1 Answer

Creo Developments CS Ltd

Rating: 5 out of 5

Trowbridge

As a rule of thumb a birds mouth notch on a rafter should be no less than one third of the timber width and no more than half. So for example; on a 4x2" (100x50mm) the deepest point of the birds mouth notch where the plumb and seat cuts meet should be at least aprox. 33mm in from the underside edge of the rafter, and certainly no more than 50mm. You will find this gives you a good surface area seat cut for fixing into wall plate, whilst maintaining good strength structurally down to the eaves. Hope that helps.

Answered24 January 2015