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Ford 9N, 2N & 8N Discussion Forum
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Way OT - How to cut a birdsmouth

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OK-AL

10-27-2003 18:34:38




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OK Guys,

I've added a front porch to my house. I'm in the process of putting a roof on it. But I can't figure out how to measure to cut the birdsmouth for the rafters. Every time I try to cut it, I either get the angle wrong on one end or the birdsmouth angle is wrong, or it ends up too far out.

Any carpenters out there?

Sorry for the off topic, but i've had a very hard day.

Thanks,

OK-AL

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jim

10-27-2003 20:40:27




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 Re: Way OT - How to cut a birdsmouth in reply to OK-AL, 10-27-2003 18:34:38  
Take a look at this as this is what I was trying to explain.
http://www.easyrafters.com/gableshed.htm



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KC

10-27-2003 20:39:31




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 Re: Way OT - How to cut a birdsmouth in reply to OK-AL, 10-27-2003 18:34:38  
For about 10-12 bucks pick up a Swanson Speed square. It comes with a book that explains how to cut hip and common rafters.Every tool box needs one. Good luck



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Colin in WI

10-27-2003 20:27:56




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 Re: Way OT - How to cut a birdsmouth in reply to OK-AL, 10-27-2003 18:34:38  
Try downloading the free trial software from these folks. It's pretty easy to run and gives you everything you need to make your cuts. I have no connection with these folks...just have used it and like it.



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JimNC

10-27-2003 20:15:19




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 Re: Way OT - How to cut a birdsmouth in reply to OK-AL, 10-27-2003 18:34:38  
Hope this helps. This is a page out of a book I have. Its huge so it might take a few minutes to load after you click the link.

Jim



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Kenny

10-27-2003 20:18:46




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 Re: Re: Way OT - How to cut a birdsmouth in reply to JimNC, 10-27-2003 20:15:19  
Excellent !!! JimNC You provided the best Help



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Kenny

10-27-2003 20:06:33




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 Re: Way OT - How to cut a birdsmouth in reply to OK-AL, 10-27-2003 18:34:38  
If you know the Pitch of the Roof your building take framing square & pitch inches on short side & 12" on long side. 4/12 Pitch would be 4" & 12" .
Outside of Square both sides line on bottom of rafter. you can slide it down & cut tail if you figure how much overhang you want.



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Jerry (AL)

10-27-2003 19:47:51




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 Re: Way OT - How to cut a birdsmouth in reply to OK-AL, 10-27-2003 18:34:38  
I'm not a carpenter so I am trying to figure out what a birdsmouth is. I've not heard that term before.



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jim

10-27-2003 19:45:05




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 Re: Way OT - How to cut a birdsmouth in reply to OK-AL, 10-27-2003 18:34:38  
Do you know the pitch of the roof?
Does it drop 4 foot for every 10 feet of run?
How much does it drop in every 10 feet?
Need to know to calculate angle.
Do you have a carpenters square?
Jim



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Nailbender

10-27-2003 21:46:16




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 Re: Re: Way OT - How to cut a birdsmouth in reply to jim, 10-27-2003 19:45:05  
Send me your email address and I will email you a page of rafter lengths for any span or pitch you want. A 4/12 roof on a building 20 ft wide the rafter will be 40" in the peak. 1/2 of building width = 10' X 4" = 40 inches



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OK-AL

10-27-2003 19:52:40




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 Re: Re: Way OT - How to cut a birdsmouth in reply to jim, 10-27-2003 19:45:05  
It's a 4 in 12 pitch. Yes, I have a carpenter's square. Getting the birdsmouth at the right spot on the rafter is a big problem.



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Sam#3

10-29-2003 06:39:16




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 Re: Re: Re: Way OT - How to cut a birdsmouth in reply to OK-AL, 10-27-2003 19:52:40  
The rafter table on the square will give you the 'length of rafter per foot of run.' For 4 in 12 thats 12.65". You must interpolate any fractional foot.



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Jim

10-27-2003 20:31:59




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 Re: Re: Re: Way OT - How to cut a birdsmouth in reply to OK-AL, 10-27-2003 19:52:40  
I hope someone besides me can tell you how to do it but I would put the square on the bottom of the rafter,4" on one leg and 12" on the other leg and this should give you the proper angle.

If you can measure the distance from the center of the roof to inside of the outside wall plate. Important! This measurement must be a horizontal measurement and not along the slope of the roof. On the ground or concrete apron or driveway or floor, strike a straight line the same length that you just measured. From one end of that line draw another line square with that line the same length as the height from the top of the wallplate to the peak. Lay the peak end of the rafter on the end of the short line and rotate the rafter down to the end of the other line. This should give you the location and also the angle to cut the birdsmouth.
I built my own house and (2) pole barns this way and they all came out fine. I am not a carpenter.
There must be an easier way but this is very accurate and my brother in-law who is a carpenter was amazed.
Hope this works O.K.
Jim
Please let us know what happened.

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buck

10-27-2003 20:20:45




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 Re: Re: Re: Way OT - How to cut a birdsmouth in reply to OK-AL, 10-27-2003 19:52:40  

Well since you have a 4/12 pitch lets say that the virtical leg of the birdsmouth will be 2" and the horizontal leg will be 6" (same 4/12 on your square) With the house end of the rafter cut for a proper fit,lay the rafter in place but raise the house end up the 2"(birdmouth vertical) and mark the rafter at the edge of the needed birdsmouth at the outside header. Now use the square at 4/12 to mark the birdsmouth. Should your house end of the rafter happen to be to fit a wall with hangers or ledger board then square that rafter before you make the 12/4 cut and then the scrap wedge can be used to mark the birdsmouth insuring exact angles. Trial fit this rafter and use as pattern. Hope this helps.

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Kenny

10-27-2003 20:15:22




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 Re: Re: Re: Way OT - How to cut a birdsmouth in reply to OK-AL, 10-27-2003 19:52:40  
Use Chalk Line on Floor or Square a couple of 2x4's & lay your rafter on it at correct angle. Measure out from Squared corner to the distance your Porch is deep to outside of wall. This should be where you want cut Birdsmouth. Does this help or do you need more info. ???



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OK-Al

10-29-2003 07:51:20




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 Re: Re: Re: Re: Way OT - How to cut a birdsmouth in reply to Kenny, 10-27-2003 20:15:22  
Thanks to everyone who responded!! I used a couple of your ideas, figured out what I was doing wrong and nailed it!! (Literally).

Really appreciate this board. Has helped me on my 8N many times.

OK-AL



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