roof angle

[AriLovesChickens]

Clueless newbie construction question...

According to the plan for this coop, it is 54" inches on the front side and 43" on the back. But I can't see any angles on the ends of the side frames. Is it possible to just put the sides together and hammer on the roof section, without cutting any angles??

 

[MadChickensVT]

Looks like they notched the rafters over the front wall. It's hard to see the others. Can you post a link?

 

[AriLovesChickens]

I don't think any of the other pictures are any better, but it's from here:
http://thetanglednest.com/2010/02/our-urban-chicken-coop-plan/

 

[MadChickensVT]

Yeah, hard to tell. It's not too big so the loads won't be much, it shouldn't need the joints to be perfect. Care to share why you don't want to cut an angle?

 

[AriLovesChickens]

It's not that I don't. I'm just trying to figure out how to make this, with no construction knowledge whatsoever. I'm trying to get all the board sizes and angles from looking at that picture (and the limited plan link down the page). Any advice is appreciated!

 

[MadChickensVT]

You can cut the boards slightly longer than needed, place them behind the board they are joining, and trace the angle with a pencil. That's how I did my rafters.

Or if you want to do the math, figure out your rise and your run, meaning how much the height increases and how long the horizontal is.

Then plug those numbers into a right triangle calculator, like the one here http://www.csgnetwork.com/righttricalc.html

Tracing the angle is much more reliable because things can be off a little bit from the math.

 

[wyododge]

If you would like to frame with angles, this is the long hand method.

a2+b2=c2

A= 54-43
B= depth of coop
C=Length of roof section from front to back.

The cut on the top of the post is Parrallel with the hypotenuse or Leg C.

That angle can be found by the following:

A = difference in height from between front and back of coop. We'll call this the short leg = 9"
B= Depth of coop We'll call this the long leg
C=the roof or hypotenuse.

The angle where the roof touches the front wall is a
The angle where the roof touches the rear wall is b

If you imagine you coop is built as a square with a triangle on top creating the roof angle, this is the triangle we are figuring the angles for.

The value of angle a = sin (opposite(A)/hypotenuse(C)).

If your coop were 48" deep, this is what we would be looking at...

A=9", B=48"

We are looking for C, a, b.

C=the square root of (9(squared) + 48(squared) = 48.84"
a=Sin(9/48.84)=10.62*
b = 90 - 10.62* or 79.38

The value of angle b= angle a - 90*. The angles inside a right triangle must = 180*.

Now we have all the angles of your roof triangle. The angle of the cut on the post(s), will be the value of angle (a) swept up from horizontal, or the value of angle (b) swept up from vertical. It is the same for both posts.

You can also use rise run.

Rise is 9" run is 48" so 9/48 or 4.5/24 or 2.25/12, pretty close to 2/12 pitch. If you have not cut anything yet, use the 2/12 value to frame your end walls. In essence, let the roof slope dictate the wall heights. It should be less than an inch difference.

Always use math to frame a roof and walls if you want them to be square and true. It ALWAYS works. Just make sure to take your time, always measure from the same point of reference (i.e outside of timbers or inside of timbers), and double check your measurements. After you have calculated your angles, and have your boards marked, clamp a straight edge on it and make sure it looks right. When it looks good, frame to your marks and everything will fall right in line, because it has to. Math does not lie.

The only place I run things long is rafters, and that is because I like to make sure the over hang planned on is enough, or possibly to much.

And you said you would never use that algebra crap in the real world!!! HA!

HAPPY FRAMMING!!!!

 

[AriLovesChickens]

Algebra, I liked. Geometry, not so much! That's geometry! Thanks, I'll try to digest it tomorrow.

 

[Mac in Wisco]

Quote:
Yes, it looks like the rafter is notched to fit on the top plate of the front wall, the middle stud has had the top trimmed to make a saddle for the rafter. I'd guess that the back is probably notched too, since they did it on the front.