New coop roof question.... need help ?!?!?!

No worries. It appears you want to raise the roof 12 inches over a span of 4 feet? That is a 12" / 48" or 4/12 pitch roof. The angles of your cuts will be 18 1/2 degrees. For each foot of span, the rafters will be 12.65 inches, or in your case, roughly 50 5/8 inches to the outside of each wall. If you want to add overhang......say 6 inches or so, add that to the overall length of your rafters. (6 inches top and bottom would be 12 inches overall, so 12" plus 50 5/8" = 62 5/8").

If you want to make this easy on yourself, head off to the nearest hardware store and buy yourself a Swanson's Speed Square. Get a Swanson's that has the little blue book with it. All you need to know is in there, including the table that gives you the angles and rafter lengths, along with instructions on how to layout and cut a birdsmouth rafter joint. Easy once you know how to do it.......but so is brain surgery!

You can cut the overall length with a chop saw, but may need either a skillsaw, jigsaw or handsaw to do the birdsmouth cuts.

I gotta say.....once anyone has struggled with making these relatively easy cuts......easy in comparison to a complicated hip roof.........you will walk away with a new found respect for a house framer. They do it every day and make it look easy. It's not.

 

Something I’ll add is to make sure you use appropriate hardware to attach the roof material, rafters, and purlins. Don’t let the terminology worry you, use appropriate hardware for what you are attaching. When you attach the roofing material (whether metal, wood, or plastic) use screws or ribbed nails long enough to grip well. Screws really grip well. If attaching wood to wood, use either screws or nails long enough to grip well. Use ribbed nails if you use nails. I lost a roof on a loafing shed that was here when I moved in because they used 2-1/2” smooth nails to attach the rafters to the purlins. A strong wind blew it off. A section 12’ x 8’ flew over 200 feet, hit the ground and bounced over my cars. It landed in my front yard on the opposite side of the house from the coop. No damage to cars or house. I was lucky.

People tend to think only of the main materials they use but connections are just as important.

 

I need to make a correction. A roof with 12" rise over a 48" span has a rise of 3 inches per foot of run, not 4 [ (12/48)* 12 = 3]. *

So on a rafter table, you would use the 3" rise numbers.......cut angle of 14 degrees and 12.37 (12 3/8") per foot of run. So with a 4' run (48" to the outside of each top plate) the rafter cut would be 49 1/2 inches, plus whatever extra you want to add for overhang. (I used 6" over hangs, so I added a foot to each of mine, leaving me with scrap from an 8' - 2x4. If you used 4" or 5" overhangs, you could probably get two rafters from a single 10' - 2 x 4) with almost no scrap left after your cuts.)

* I should have remembered this.....I just cut about 5 of them to this angle and this length for the scratch shed on the Woods house I just built. Hell to get old.

BTW, 3" rise per foot of run is a good angle and slope to use on a monoslope, shed style roof.

I too had a speed square I got from Ace Hardware. The Swanson's has different and better markings for doing rafter cuts, and comes packaged with the Little Bue Book with instructions on how to make these cuts and the table of angles, rafter lengths, etc. The square is free......the thing of value is the Little Blue Book. If you know what you are doing, you can also mark your rafter cuts with a standard carpenters framing square, which is a truly amazing tool also.......if you know what you are doing.

 

I'll second this notion. All the box stores sell hurricane clips, which are light in weight and do not cost very much. The strength they add to a rafter joint is impressive. For the cost, I'd suggest most of us home builders consider using them. The Woods hen house I built just went through a violent thunderstorm, with enough straight line wind to flatten a patch of sweet corn adjacent to the house. It shrugged it off with no worries......but I built it so it would.

 

That is pretty much exactly how I did mine......T1-11 siding and shingles over plywood roof. I used white shingles, which reflect the sunlight and seem to be cooler in upper 90 degree heat. Also, shingles and plywood roof do not sweat and drip moisture like a metal roof does. If you did use metal roofing, put an insulation barrier down beneath it.

On T1-11 siding, quality seems iffy compared to the last time I used it (for a dog house), but now that it is up, it looks better. It is getting a bad rap regarding rot and weathering and likely for a good reason......it is tough to paint correctly. If you don't care what color it is, you can use an oil base stain on it. But I wanted mine a solid "barn red" to match an adjacent horse barn. That meant an exterior latex paint.

So, checked with a commercial painter friend, and after he was unable to convince me to NOT use T1-11, he suggested an oil base primer.....inside and out, then 2 coats of exterior latex on the outside and a single layer of high gloss white on the inside. BTW, once the panels were cut to fit, and ready to screw into place, I laid them out on saw horses and painted them while horizontal......using a 3/4" nap roller. The siding sucked up the oil base primer at an alarming rate.......about twice as much as the coverage label on the can would suggest. But that also meant I was able to get deep penetration and full coverage, including the edges and most importantly, the joint seams. Those need to be 100% sealed if you don't want rot and you can't get that if you paint it once it is up and vertical.

Tricky stuff to work with if you want it to last.

BTW, for those who might suggest the similar looking 3/8" Smart siding material, I voted against it as it is not "structural". Does not have the structural strength that the 5/8" T1-11 has. It is for all intents and purposes, 5/8" plywood, made to look like siding. The Smart siding is easier to paint and will hold up better, provided it is installed over something structural, such that it is only cosmetic.

 

Agree with all Howard stated. One other choice on siding would be the pre-primed plywood. Very similar to the T1-11 but already primed. That's what I used. Makes painting easier and the primer in the joints and on the edges makes it a bit more user friendly. It's about $4 more per sheet vs the T1-11. I've had no success with the not so very "Smart" siding products. I've tried everything, pre-priming, caulking you name it and still have rot issues. I've replaced it on my shop once and some of it is due again. I find it impossible to seal the edges well enough to prevent water being soaked up.

Dura Temp primed plywood siding

 

@TerryH , in regards to the Smart siding that you used and that failed, was this the treated version?

Thanks,
Ed