Need some help on a carpentry project.

I am building a shed in my backyard and I have gotten to a point where I am struggling to get the right angle on my rafters. I am building a simple gable roof with a 8" overhang with a standard plumb cut. The shed is 96" wide outside edge to outside edge. I want a 5/12 pitch on the roof and will be using a standard 2 x 6 as the ridge beam.

I am struggling with the birdsmouth cuts and the ridge rise. The depth and dimensions throws me all off. I am going to use 2 x 4's as rafters since it is just a shed and will be plenty strong for my needs. Does anyone have a program or the knowledge to fill in the blanks on these dimensions.

Let me know if I am missing any needed measurements. Thanks and hope someone can help.

 

Shed so far...

 

Check with OZ-T. He is a carpentry ninja.

Alternatively, it as all geometry calculations for triangles. If you know the height and width (the L part of the triangle), you can determine the length of the hypotenuse (the longest side(s) fotht triangle, your rafter length). Google geometry (or carpentry) calculators, and you should be off and running. Once you have all three sides, you can calculate all angles.

To determine roof pitch, you can look up recommended pitches and work from there, too.

 

I thought about simulating the the ridge beam. I can get that done. But is there a trick to getting the birdsmouth right? I can always trial and error. If I dont have exact dims by this weekend I will do that method. Just thinking I could get dims, and cut all the rafters at once and knock it out real quick.

OZ-T where are you???

 

oh ozzy oz where are you?!

 

http://www.pole-barn.info/roof-rafter-calculations.html

I can also fill in the blanks, but I'm kinda busy atm.

angle is 22.6 degrees

 

I think that gets me close...would the angle of the heel cut be the same as the end plumb cut?

Here's what I got from that site:
Overall Rafter Length: 4 ft 11 7/8"
Ridge to Wall Length: 4 ft 3 3/16" (would this be the dims from the peak to the birdsmouth?)

 

Someone feel free to correct me if I pooched the screw...

p.s. Generally you make the seat cut of the birdsmouth as wide as the member it's sitting on, but the 3-1/2" here cuts into the rafter quite a bit so I cut it to 3" in my example. If you make the seat cut 3-1/2" the heel cut becomes 1-7/16" instead of 1-1/4".

 

What is the width of your exterior wall framing ? 2x4 or 2x6 ?

 

I'll assume you framed your exterior walls with 2x4 .

Layout a 22.5 degree plumb cut at the top and cut it .

Hook your tape onto the long point of the angle and measure down the top of the rafter 51 1/8 , draw another plumb line the same as the one on the top , this represents the exterior wall line .

Continue measuring down the top of the rafter and make another plumb line at 59 3/4 , this is the total length of rafter including the 8" overhang .

To cut the birdsmouth , draw a line square to your plumb line you marked representing the exterior wall , the level leg of the birdsmouth should be 3 1/2" . Do not over cut .

I'll post a pic , hang on

 

96" outside width with 2x4's.

Thanks

 

I'll check in here if you have some more questions

Are you putting plywood on the frame ?

 

this shit is so confusing...

*trying to learn for future referance..*

 

X2, Learn something new everyday!

 

You guys are a huge help. I am going to decipher all this info tonight after work and draw up some lines on a 2 x 4. I will shout back if I get stuck. Thanks again. This is a huge help.

 

Yes plywood for the roof, tar paper then regular asphalt shingles.

 

I meant the walls .

 

I will use some cheap 4 x 8 siding more than likely...Menards usually has it for $15 a sheet or so. I am going to paint it the color of my house so I want it to be pretty decent stuff.

 

yeah some pretty useful info here

 

You may want to over size the birdsmouth by the siding sheeting + a hair so that you don't need to notch around all the rafter tails .

I can explain this if needed , but won't confuse the issue if you don't want to do that .