Stick built attic framing

How do you like this birds mouth? 10 YO home. One rafter was split from top to bottom.

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Not sure why the framer elected to cut the tail of the rafter to the size of a 2x4 or 2x6 but the seat cut is fine. The fact that it does not have a plumb cut to make a notch is not necessary…much like trusses, it just makes installing a little bit more of a pain since you can slide the plumb cut up tight to the top plate.

If you feel the tail of the rafter has been slightly compromised then a carpenter can simply sister another tail next to the existing tail.

Missed it by that much!
Oh the bird mouth has to go tight into the top plate.

Very unconventional. The only reason I can see for this is to get more insulation over the top plate. I would not say it was wrong unles you are calling into question the plumb cut. They over cut it and will need repair.

My understanding on this is that the birds mouth keeps it secured at the top plate. Your picture shows very unconventional building practice. I would call it out since more than 1/3 has been removed to provide a birds mouth, it was over cut and put in the wrong place. This to me shows the stick framed roof even though very strong design was not built by a professional framer. I would want to see collar ties on every rafter for this one.

There is no birds mouth on a truss… what keeps it secure are proper nails at the seat cut. The birds mouth does help with installation when you are pulling them in place.

The only issue I see is what I pointed out earlier…the plumb cut looks like it went to far up thereby possibly weakening the tail section (overhang).
Simple fix, just sister a 2x4 onto it.

Collar ties are not necessary for every rafter…every 48" will suffice.

On a side note it looks like this rafter is a 2x10…which means the ridge board should be at least a 2x12 (one inch nominal actually)…maybe even greater depending on the pitch of the roof… I suspect the pitch is a 10/12 or greater looking at the end of the tail.


For one thing it is not a 2x10 but a 2x6. The reason I would recommend collar ties is until they got the proper repairs. As for the comment on a birds mouth. Correct as it is not cut properly and even if it was moved back to secured position it still will not pass.

I wonder why the seat wasn’t level cut out to the tail. And, I agree with Jeffery. If over cutting and splitting is problematic, sister them.

Betcha a strawberry shake that its not a 2x6 rafter but a 2x10 whose tail was cut as a 2x4…:mrgreen:

Collar ties have nothing to with it…the purpose of a collar tie is for uplift…not downward forces…I will betcha a banana split on that one. :wink:


Wrong. Look at pic #2 with the tape measure!

Also… I agree completely with Jeff’s opinion.

Opps! you are right, that’s what I get for posting before having breakfast. I multiplied by three but was thinking 1 1/2 inches not 3 and since you mentioned this where is that in

I referred it to a licensed and competent GC for repair as deemed appropriate and reminded them that structural work requires a permit. Like I said before, one rafter was splice lengthwise in half the entire length.

Do I get a strawberry shake out of it…:mrgreen:

As a builder I have built hundreds of homes and have cut thousands of rafters… I better know what a 2x10 looks like and how to install them. :slight_smile:



You win the Strawberry Shake!!! so you are the one cutting those rafters wrong. LOL

I think they were attempting a raised heal truss.
Look at the saw cut. It goes another 2" into the rafter or truss.
Very pour rough carpentry skills.
Or good beer.:wink: