Roof construction help please

[MACCanadianCoop]

Hi everyone, I need some input from those with construction know-how. I'm building a walk in coop with a sloped roof, front to back, to mitigate snow removal. The coop is 81 inches (6 3/4 feet) deep and the front wall will be approximately 92 inches (7 2/3 feet) high. I want a 6 inch overhang at the back (that side is protected by trees) and a 2 foot overhang at the front.

My question is how high do I need the back wall to get the right slope?

 

[3KillerBs]

I can't help you, but I know who can.

@U_Stormcrow @aart

I see that you're in Canada. What are the standard lumber dimensions there? It's always easier to work with those than to have to make a ton of cuts.

 

[U_Stormcrow]

Simple Geometry.

How big do you want your roof material sheet to be?
Alternatively, what slope do you want?

You have offered two "X" to determine, and we can't solve one without the other.

I'll make a picture in a moment to illustrate.

 

[U_Stormcrow]

Give me one "X", and its easy to solve for any other.

 

[MACCanadianCoop]

I can't help you, but I know who can.

@U_Stormcrow @aart

I see that you're in Canada. What are the standard lumber dimensions there? It's always easier to work with those than to have to make a ton of cuts.

Same as anywhere else?

 

[MACCanadianCoop]

Simple Geometry.

How big do you want your roof material sheet to be?
Alternatively, what slope do you want?

You have offered two "X" to determine, and we can't solve one without the other.

I'll make a picture in a moment to illustrate.

I know the overal length of the roof depends on the slope x the depth of the base. But I don't know how to determine what angle of slope I need. I'm not educated in construction jargon, so I don't know how to translate the information I'm finding on the net

 

[U_Stormcrow]

Examples:

Let's say "X" the roof measurement is 10' Because of fthe shelf 10' panels are at least somewhat available, as is 10' lumber.

If the Base is 9.25' and the Hypotenuse is 10', then "Y", the total elevation (height) of the roof is the square root of (100 {that is, 10^2} - 85.5625 {that is, 9.25 ^2}). Solved, that's the square root of 14.4375, or 3.7997' (almost 3' 10").

That doesn't tell you how tall the back wall is, of course. That's 7.67' - "Z"
However, since the slope is constant, we know that "Z" must equal (6.75 {Depth of Shed} / 9.25 {total depth of structure including overhangs}) * 3.7997 {Y}. That's 2.772' Call it 2' 9". If the Front wall is 7' 8", and the back wall is 2' 9" shorter, then the back wall is 4' 11".

Simple. and for what its worth, that's approximately a 5/12 pitch, which is quite common in roofing construction.

 

[MACCanadianCoop]

Ok, so if I do a 5/12 pitch (5 inches of height for every 12 inches if length, yes?) then how high should my back wall be please?

 

[U_Stormcrow]

Ok, so if I do a 5/12 pitch (5 inches of height for every 12 inches if length, yes?) then how high should my back wall be please?

4' 11", as I calculated above.

 

[MACCanadianCoop]

4' 11", as I calculated above.

Oh, I got it. At first i thought 9.75 refered to Base of the coop but I see now that's length of roof. Thank you!!