# Determining pitch and birdsmouth cuts



## ktee (Aug 21, 2011)

My building I'm constructing is 12 ft wide, shed roof. The front wall is full 10' studs(plus the 3 plates) The back wall is 8' common(92 5/8") studs. I'm not using ceiling joists. I'm having a hard time figuring the pitch and how to cut the birdsmouth for the 2x6 rafters. Please help this novice builder. I want a 2'overhang on both front and back. Thanks.


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## kwikfishron (Mar 11, 2010)

Welcome to the forum.

You can just hold a piece of rafter stock up against the two walls where you want the rafter positioned and “scribe” the birds mouth. You can then transfer the plumb cut of the BM to the plumb cut of the rafter tails. Then use that first rafter for a pattern to cut the rest. 

You can build the entire thing without ever having to know what the pitch is.


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## ktee (Aug 21, 2011)

Thank you, I appreciate the info and the welcome. I've been lurking for a long time and have learned a lot. I'm just a wannabe carpenter, who is having a great time building a small passive solar building. You have solved what I thought was going to be a big problem, the math was beyond me! Thanks again!


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## kwikfishron (Mar 11, 2010)

Glad to help, sometimes the best solutions are the simplest ones.

Good luck with the rest of your solar project. Post some pictures in the “project showcase” section if you like. I’m sure your solar building would interest many.


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## Marbledust (Jun 26, 2010)

FYI,

put the rafter on top of the plates...use a 2 foot level and pencil in the vert. lines on the rafter..determine the notch depth...use a square to mark horizontal cut


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## ktee (Aug 21, 2011)

Thanks! I'm so glad I posted this question here. I had lost sleep over this!


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## adam_withrow (Aug 29, 2011)

in the future, just compare rise to run. in your case, you have 2' of rise in 12' of run. 

sooooooooooo....


reduce that number so your run is 12" and you've got your common pitch.

for example, a 6/12 pitch roof rises 6 inches for every 12 inches the roof runs.

in your case, and you got lucky with your dimensions, you have a 2/12 pitch.

that means you use the 2 common mark on your speed square.

thennnnnnnn....

find the complimentary angle to that (subtract actual degrees from 90) and make your line from the stop point on the first line to the point where the actual degree number causes the two lines to intersect.

so 2 common is 10 degrees (ish) and the complimentary angle to that is 80 degrees.

OR you can just use your framing square and do a 90 off of your first line.


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## sixeightten (Feb 10, 2009)

Your pitch will be about a 2.25/12 if you make both birdsmouths the same height. 10' 41/2" minus 8' 1 1/8" equals about 27 3/8". If the walls are truly 12' outside to outside, this will be very close.


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## ktee (Aug 21, 2011)

Finally got a picture to post. Thanks for all the advice and the knowledge I've gained from popping in here for the past couple of years. 
http://www.diychatroom.com/members/ktee-124470/albums/camp-house/


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## adam_withrow (Aug 29, 2011)

that's coooooool!

=)


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