rafters

[Sifu]

Looking at the notch depths for rafters out of 802.7. It limits notches to 1/6th the depth of the member. Does the 1/6th limit come from the call size of the lumber or does the 1/6th limit get taken from the plumb distance of the rafter in use, allowing a deeper notch? I have never had to look too closely at this provision until now, where some of the locals seem to be pushing the minimums to the limit. Also, I assume the 1/6th limit is correct since the notch is not at the end of the rafter but it does seem restrictive so enlighten me if I have it wrong.

 

[imhotep]

So you are not referring to a 'birdsmouth' cut, but a notch away from the wall?

1/6 d. So for a 2 x 10: d = 9.25" x .16667 = 1.54" notch measured perpendicular to the edge of the member.

 

[Sifu]

Sorry, I am referring to the birdsmouth, it just seems like 1/6 is a lot more restrictive than what I thought.....unless the tail doesn't count and you use the end notch limit of 1/4.

 

[imhotep]

Sorry, I am referring to the birdsmouth, it just seems like 1/6 is a lot more restrictive than what I thought.....unless the tail doesn't count and you use the end notch limit of 1/4.

1/4d at the end (bearing). The tail does not move the notch away from the end (bearing). The tail could be eliminated without affecting how the member resists and transfers the loads.

 

[DRP]

The birdsmouth is not a notch in the sense of this requirement, just as the cut end of a joist is not a notch. It is an angled bearing seatcut. It should not extend inboard of the wall. If a rafter tail extends outboard of the wall there must be 3.5" of wood (measured perp to grain) remaining above the birdsmouth for an overhang of 2' or less.

If it was a problem for the inspector on the jobsite I'd make the rafters bobtails and scab cantilevered tails on.