Houzz Logo Print

Why does is a roof rafter birds mouth cut depth limited to 1/4?

dont tread
3 months ago

IRC limits birdsmouth depth cut to 1/4 the thickness of a roof rafter or it creates a weak point. How exactly is there a weak point?

Say you have a 2 x 8 rafter and a 2 x 6 wall, some would think it would make more sense to have a wide birdsmouth cut so more surface contact is made with the rafter and top plate - however IRC says this makes weakpoint. How is this a weakpoint? If there is no rafter tail would there still be a 1/4 depth limit?

Comments (10)