# How deep to cut birdmouth and seat of Rafters



## bhollehday (Jan 30, 2015)

Building a open ceiling roof for a 10x12' shed in california using 2x6's, 4:12 pitch, no support trusses only collar ties, double top plate, and a 2x6" ridge board.

My question is when cutting the birdmouth and seat, how deep should the birdmouth be? I have a double top plate so If it was single top plate I would cut the seat cut so its at 3.5inches wide and little over an inch deep, but seems like you want the bird mouth to overlap a little of the second top plate as well, so should I go deeper as seen in the attached?

Also Ive got 4 framed walls up and no siding or roof. I plan on putting top plate on, putting diagnols across the inside of the walls to keep square, maybe throw a couple of peices of siding on the corners, then start putting the roof up. Anyone have any better tips or objections? Also any tips for collar ties? How long do they need to be?

Thanks


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## ront02769 (Nov 28, 2008)

I would just cut it wherever it naturally falls....since the double top plate is doubtless double nailed with like sixteen penny nails down into the bottom top plate over every stud, hence going a half inch into the stud also. Ron


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## ron45 (Feb 25, 2014)

Hope this helps..

https://www.youtube.com/watch?v=lr4NwLx_ctk


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## woodworkbykirk (Sep 25, 2011)

having the birdsmouth deep enough for it to lap down to the first plate of the double is redundant. in fact it can actually make it so it wont pass inspection if your require one. standard practic is to have a seat cut that is no less than 1 3/4" or to not exceed 1/3 of what the plumb cut angle is on the rafter stock.. i.e if your plumb cut at the ridge is 7-3/8" = a vertical cut of 2-7/16"


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## ron45 (Feb 25, 2014)

Here's a just in caser.........

https://www.youtube.com/watch?t=167&v=fBxcx6YKz54


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## bhollehday (Jan 30, 2015)

ront02769 said:


> I would just cut it wherever it naturally falls....since the double top plate is doubtless double nailed with like sixteen penny nails down into the bottom top plate over every stud, hence going a half inch into the stud also. Ron


Where it naturally falls? Im just debating on the depth of the "heel cut". Should I cut it deep (but not past 1/3 rule of the 5.5") or cut it so the seat cut is 3.5" and comes flush with the inside of the wall (which leaves a little over 1inch deep on the heel cut) what do you mean by naturally falls?

Or should I just cut the dam thing Im probaly worrying about it too much :huh:


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## bhollehday (Jan 30, 2015)

woodworkbykirk said:


> having the birdsmouth deep enough for it to lap down to the first plate of the double is redundant. in fact it can actually make it so it wont pass inspection if your require one. standard practic is to have a seat cut that is no less than 1 3/4" or to not exceed 1/3 of what the plumb cut angle is on the rafter stock.. i.e if your plumb cut at the ridge is 7-3/8" = a vertical cut of 2-7/16"


That's exactly what I needed! Thanks a lot!


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## woodworkbykirk (Sep 25, 2011)

no worries at all. bettet to build to code than to have to tear it apart and start from scratch.. just make sure you check with what your local codes are first


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## ron45 (Feb 25, 2014)

Fellas, don't make it harder then it has to be...
If you follow the steps/rules to the method used you will always have a sound build that meets or exceeds the codes.
With that said, there are only two ways to cut a rafter. The right way and the wrong way.
Each method used has steps and rules, deviate from any portion and you have just cut the rafter the wrong way.

In my opinion the video in post #5 is the best method used, I only wish I could have explained it that good.


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## woodworkbykirk (Sep 25, 2011)

how about posting a video that actually has sound. and the guy in the video overcuts his birds mouth which weakens the rafter.. its a big no no.. finish the cut with a handsaw or jigsaw


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## bhollehday (Jan 30, 2015)

Good tip thank you. The sound is good btw it's just mono and only left or right I was trippin to trying to figure out how he's going to make a video with no sound haha


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