A few Q's: Roof Pitch, Sheathing...

[762]

In designing my coop, I am wondering if the minimum 3-12 pitch is sufficient for a lean-to style coop (no A-frame). The coop will either be 8 or 12' wide (sides) and 12' long (front/rear). Roof will slope from front to back. It will be located in a small grove of trees, and a gutter will run along the rear. It will be on approx 3' stilts (depending on the ground slope), and the coop itself will be 6' tall (additional height in front for the roof...2' for 3/12 pitch on 8' wide coop). So with that in mind, the front is already over 11' high. We don't get a lot of snow. ONCE in awhile we can get 8-12 inches but it is super rare. Usually a couple of 3" snows per year if we are lucky. Will most likely be using a metal roof. With a metal roof is sheathing required? I've seen a lot of folks use...I dunno...stringers? Just horizontal 1x4s spaced out...looks like very 16-24 inches.

I am in a pretty hot, humid climate (Central Virginia). We get cold days but usually the winter temps stay in the 40s or higher and overnight temps the 20s or higher. There are exceptions but as a rule, our winters are MILD.

That being said, for the walls of the coop, I've seen folks just do T1-11 siding straight over the framing. I've seen some folks just do sheathing and paint it. And I've seen sheathing topped with siding.

In the end, the coop is about functionality and not looks. I like some of the Carolina Coops ideas but good grief, I certainly don't need mine to look like a residential home. I need it to be well-built and well-protected. If siding on top of sheathing helps with that, fine. If siding is enough, fine. I know how to properly caulk and paint exteriors, so the wood will be protected.

Not sure if it matters, but the run will also be a lean-to butted up against the front of the coop below the top venting (pitch angle opposite of coop's), and will be covered but completely open air from side to side. The run will extend well past the 12' width of the coop...probably another 20'.

 

[perkolator]

I don't have snow but I'd guess that pitch will be sufficient, just make sure to frame it to handle the snow load. Keep in mind most off-the-shelf roof panels are up to 12ft length, so that may determine your dimensions if you were trying to do that 12ft mentioned and put a roof over it. Adding extra sheet materials is up to you and your budget, personally I am in the "it's just a chicken coop" mentality and would skip it.

My coop has a corrugated metal roof installed directly over purlins without any sheathing underneath - I felt no need to add extra weight and cost. I did choose to cover over the sheathing on the coop structure, for aesthetics mainly and also because I used OSB plywood instead of something like ACX plywood or sheet siding that has more moisture-resistance.

Good luck with the build!

 

[aart]

I am wondering if the minimum 3-12 pitch is sufficient for a lean-to style coop

Will be fine for rain runoff.
My house is 3/12.

That being said, for the walls of the coop, I've seen folks just do T1-11 siding straight over the framing. I've seen some folks just do sheathing and paint it. And I've seen sheathing topped with siding.

That will be fine.

 

[saysfaa]

The reason warranties require at least minimum slope is so the water runs off fast enough to not puddle in low spots or behind fasteners. And to shoot off the edge instead of hugging the edges around under the panel and getting the wood under the roof wet.

3:12 is what warranties require (there may be other requirements). Anyway, it can work but doesn't leave much margin for things like installation errors. If you are also going with minimum rafters/purlins it can still work but you may need to be more careful to get them all straight than you otherwise would need to be.

Have you considered making the back wall a little shorter instead of the front wall taller? You may never notice the loss of headspace if you have a roost across the back wall. Or if you were planning 8' walls.

A steeper roof should improve air flow also but it might be abundant enough anyway to not matter.

Sheathing under a metal roof is not needed for support. It is sometimes used so the roof doesn't rain inside due to condensation. Not all metal roofs will rain inside; it depends on climate and probably other things. I don't know much about when it does and doesn't other than the basics (warm, moist air hitting cold roof). There are other, less expensive, options than sheathing under the metal panels even in climates/conditions that it is a problem. The best commercial builder of sheds in this area uses a very, very thin layer of closed cell foam insulation on the underside of the roof panels. I think the foam is attached to the roof panel but I'm not sure. Anyway, it goes over the purlins too.

 

[AnnPann]

Sheathing under a metal roof is not needed for support. It is sometimes used so the roof doesn't rain inside due to condensation. Not all metal roofs will rain inside; it depends on climate and probably other things. I don't know much about when it does and doesn't other than the basics (warm, moist air hitting cold roof). There are other, less expensive, options than sheathing under the metal panels even in climates/conditions that it is a problem. The best commercial builder of sheds in this area uses a very, very thin layer of closed cell foam insulation on the underside of the roof panels. I think the foam is attached to the roof panel but I'm not sure. Anyway, it goes over the purlins too.

I am in the process of building a new coop with a sloped metal roof. I took a gamble on the condensation in order to save $, and not sure yet it was a good one. Build is still underway, and we had an unusually cold rainy day for this time of year, then it cleared overnight. Next morning, I had some condensation dripping into the coop/run. It wasn't exactly "raining", but I could see the mulch below was wet where it had fallen. It's way too late to go back and add plywood, so I'm monitoring and if it gets bad enough to be an issue, I'll have to figure out a way to run something between purlins to absorb or divert the drips.

 

[762]

The reason warranties require at least minimum slope is so the water runs off fast enough to not puddle in low spots or behind fasteners. And to shoot off the edge instead of hugging the edges around under the panel and getting the wood under the roof wet.

3:12 is what warranties require (there may be other requirements). Anyway, it can work but doesn't leave much margin for things like installation errors. If you are also going with minimum rafters/purlins it can still work but you may need to be more careful to get them all straight than you otherwise would need to be.

Have you considered making the back wall a little shorter instead of the front wall taller? You may never notice the loss of headspace if you have a roost across the back wall. Or if you were planning 8' walls.

A steeper roof should improve air flow also but it might be abundant enough anyway to not matter.

Sheathing under a metal roof is not needed for support. It is sometimes used so the roof doesn't rain inside due to condensation. Not all metal roofs will rain inside; it depends on climate and probably other things. I don't know much about when it does and doesn't other than the basics (warm, moist air hitting cold roof). There are other, less expensive, options than sheathing under the metal panels even in climates/conditions that it is a problem. The best commercial builder of sheds in this area uses a very, very thin layer of closed cell foam insulation on the underside of the roof panels. I think the foam is attached to the roof panel but I'm not sure. Anyway, it goes over the purlins too.

Oh yeah...PURLINS. Forgive my lack of vocab...never framed anything before. Built a porch swing, entryway storage bench, cornhole boards. And an outdoor brooder.

Excellent info. I will look into the cell foam...that sounds like the ticket. As far as making the back shorter, I could do that. But I want to be able to get inside easily (human access/clean-out will be from the rear). It seems much easier to frame something a rectangle that's 6' all the way around, and then slap an additional 2' frame on the front (almost the entire 2' will be open ventilation...no windows). So basically for the wall studs I was planning on buying 2x12s and chopping them all in half.

 

[3KillerBs]

Will most likely be using a metal roof. With a metal roof is sheathing required? I've seen a lot of folks use...I dunno...stringers? Just horizontal 1x4s spaced out...looks like very 16-24 inches.

Installing metal roofing over purlins is remarkably easy and very well suited to a chicken coop in a warm climate. @U_Stormcrow helped me with mine when we were building Neuchickenstein.

Build is still underway, and we had an unusually cold rainy day for this time of year, then it cleared overnight. Next morning, I had some condensation dripping into the coop/run. It wasn't exactly "raining", but I could see the mulch below was wet where it had fallen. It's way too late to go back and add plywood, so I'm monitoring and if it gets bad enough to be an issue, I'll have to figure out a way to run something between purlins to absorb or divert the drips.

What's your ventilation look like?

While condensation can be an issue no matter what in certain climates -- requiring a thermal break of some kind under the metal -- the best way to prevent condensation is to have generous ventilation right under the roof so that the warm, moist air rises out of the coop readily.

 

[U_Stormcrow]

Very good advice above. You have largely described the first outbuilding I set on my property, actually. Depending on treecover, you may find some difficulty with the gutters clogging up with leaves that will need periodic maintenance, but other than that, you seem to have it covered.

One further comment - when I built mine, 5/4 x 6 PT "Deck boards" were actually cheaper than decent grade 1x4s, and have the benefit of being "meatier", pressure treated (in case you develop a leak at one of your screws), and wider, so its a little more forgiving if your purlins aren't perfectly true as you install your roof metal. Likely in another aise of the big box store, but definitely worthy of consideration - particularly if their 1x4s look like funny straws or are already splitting while awaiting purchase.

 

[AnnPann]

What's your ventilation look like?

While condensation can be an issue no matter what in certain climates -- requiring a thermal break of some kind under the metal -- the best way to prevent condensation is to have generous ventilation right under the roof so that the warm, moist air rises out of the coop readily.

FANTASTIC at the time I noticed the condensation the other day, as the coop walls aren’t even up yet. And there was a decent breeze.

Once built, there will still be a generous amount of ventilation. Measured in feet, of course - not inches. The entire “ceiling” of the coop is open to the sloped metal roof (which extends on out to the attached/covered run). The front of the coop will not extend up to meet the roof.

But based the fact that it’s the dripping in the current state, I’m researching options on what I can cut/retrofit in between the purlins, as I can only assume it will get worse (and harder to fix later).

Sorry to hijack original posters thread… I should start a “coop build” thread while I finish up the 2nd half of the build (which needs to be done ASAP… the new chicks arrive Tuesday!)

 

[3KillerBs]

But based the fact that it’s the dripping in the current state, I’m researching options on what I can cut/retrofit in between the purlins, as I can only assume it will get worse (and harder to fix later).

Yeah, some climates really do require a thermal break under metal roofing.

And you don't really know until you've tried it. :/