Recommended plywood thickness with a metal roof?

[Rachela]

Those who have installed metal roofing, what is general ya good plywood thickness for support and to keep condensation issues away?

 

[DougVC]

For under the roof? I just put 2x4 across the trusses and attached the steel roof to those. No need for plywood.

 

[ColoradoPip]

I used 3/8" for that. It was marked sheathing. I recycled it from shipping pallets/boxes.

Details are in my build thread
https://www.backyardchickens.com/threads/trailer-coop-build-pic-heavy.1345994/

 

[Rachela]

Okay thanks all lots to consider. My understanding is plywood helps with condensation issues.

 

[neo71665]

Down south I'd use about 1/2 inch but I don't have to worry about snow loads.

 

[ColoradoPip]

Okay thanks all lots to consider. My understanding is plywood helps with condensation issues.

That's why I did it. Many do not. Based on my reading, it is recommended but not required, FWIW

I think a range of factors play into condensation, flock size, coop size and arrangement, temps, humidity, etc. I weighed these variables and knew I did not want to fix it later, so I went with sheathing. Helps it was free!

 

[Rachela]

That's why I did it. Many do not. Based on my reading, it is recommended but not required, FWIW

I think a range of factors play into condensation, flock size, coop size and arrangement, temps, humidity, etc. I weighed these variables and knew I did not want to fix it later, so I went with sheathing. Helps it was free!

Which thickness did you use. Looks like you get snow too?

 

[Acre4Me]

If you are going to use plywood, make a traditional roof with shingles. We built elevated/walk-in coop, put plywood/shingle roof on that. Extending from both sides of the coop is corrugated metal roofing over the run. At the north end, the barn has a window, so we have clear corrugated panels at that point to still allow light into the coop. The roof is all the same height, just different materials.

 

[mowin]

I used 19/16 OSB sheathing. I wanted the extra rigidity the sheathing gives to the coop, and to handle snow load and condensation. My old home had a semi open carport, just the front was open. It would often drip from the underside of the roof due to condensation.

 

[ColoradoPip]

Which thickness did you use. Looks like you get snow too?

See my earlier post...

I used 3/8" for that. It was marked sheathing. I recycled it from shipping pallets/boxes.

Details are in my build thread
https://www.backyardchickens.com/threads/trailer-coop-build-pic-heavy.1345994/

My biggest concern are the 2-3ft, crazy wet and heavy, March snow storms that we sometimes get. Therefore I built the rafters very solid (probably overkill) with hurricane ties and proper 16" spacing. Nothing is bringing that roof down!

I also used a cathedral style roofing techniques, using a ridge beam versus a ridge board, providing even more stability and putting ~75% of the weight dispersal into the beam and walls instead of the rafters.

So in the end, with only 25% of the weight being on the rafters, add to that I did the 16" spacing and have a ton of rafters solidly built and hung properly (right amount of nails, using the right ties, etc.), I could use thin sheathing because it only serves a couple of purposes:

1) moisture barrier
2) helps distribute weight across the rafters more evenly
3) provided a nice surface to attach the purlins

I used rafters, sheathing, purlins, felt, then metal. Primarily because when condensation occurs, and it will, I do not have to worry even a little bit about it. Not only is there air circulating under the metal (because of the purlins) to assist in drying but any drips are then caught by the felt. If by chance (because I reuse a lot of materials so things have holes in them) it drips, then the plywood catches that.

Nothing gets in from above!!

I detail this all out with pictures in my trailer thread, might take a bit of digging to find which page has the right pics but they are there. It's very easy, I have no carpentry skills and had never built anything before.

Good luck