Coop wall hight???

[mowin]

Whether your coop is a walk-in or a step-up you will want to stand straight in it. At the peak to be sure but also at a or close to the sidewalls.

The front wall will be 8' high. The back wall will be 6'. I'm only 5'8", so I've got a few inches to spare, lol.

 

[aart]

I'd sheath it to stop condensation.

Ditto Dat^^^

I don't have any condensation problems in my coop or my shed. Pretty humid environment here.

Not cold there tho, that's what does it.

 

[mowin]

Ditto Dat^^^

Not cold there tho, that's what does it.

So it's in the cooler/colder months that I'll get condensation. Sounds like it would be a good idea to sheeth first, then perlings, finally metal roofing.

 

[aart]

So it's in the cooler/colder months that I'll get condensation. Sounds like it would be a good idea to sheeth first, then perlings, finally metal roofing.

If you sheath the rafters you don't need purlins.
Condensation is formed when one side of roof is cold and the other is exposed to warmer moist air.

I get condensation even on 1x sheathing with tar paper and asphalt shingles during winter thaws here. Roof is north facing and has a foot of snow on it and inside and outside humidity was near 100% during 38°F temps with rain.

 

[imnukensc]

If you sheath the rafters you don't need purlins.
Condensation is formed when one side of roof is cold and the other is exposed to warmer moist air.

I get condensation even on 1x sheathing with tar paper and asphalt shingles during winter thaws here. Roof is north facing and has a foot of snow on it and inside and outside humidity was near 100% during 38°F temps with rain.

View attachment 1687697

How cold is cold? It gets cold here---at least we think so. Be that as it may, how is condensation forming on wood as shown in your picture any better than condensation forming on galvanized metal? As you said, condensation forms when one side of the roof is cold and the other side is exposed to warm moist air. Pretty sure the temperature differential between the 2 sides of 26 gauge galvalume is a lot less than 1 inch thick planks with tar paper and shingles.

 

[mowin]

If you sheath the rafters you don't need purlins.
Condensation is formed when one side of roof is cold and the other is exposed to warmer moist air.

I get condensation even on 1x sheathing with tar paper and asphalt shingles during winter thaws here. Roof is north facing and has a foot of snow on it and inside and outside humidity was near 100% during 38°F temps with rain.

View attachment 1687697

Makes sense. Metal roofing is corrugated. Plenty of airflow. I am thinking of lining the sheeting with tar paper or ice and water before installing the tin.

 

[aart]

How cold is cold? It gets cold here---at least we think so.

Before that pic was taken and the snow got that deep,
it was single digit temps for days on end.

Either you'll have it happen or you won't,
there's no hard number numbers(that I know of),
but in colder climes(NY & MI, not SC) it's best to prevent it on metal roofing.

 

[Ridgerunner]

In Arkansas in the spring I got enough condensation on my metal roof with no sheathing that it was a pretty steady drip. The rest of the year it wasn't much of a problem. Those darn foggy spring mornings.

Condensation forms when a surface is cooler than the air temperature. The more moisture in the air and the cooler the surface is the more condensation you get. Metal will cool off faster than wood but you can still get some condensation on wood. The space between the metal and wood acts as insulation.

The bottom line is that you can get a lot more condensation on bare metal versus metal with sheathing.

 

[rosemarythyme]

Metal roofs are prone to gathering condensation. You really don't want it dripping back down. Better to put the sheathing in, I don't think it's a massive additional cost to do so.

 

[mowin]

Metal roofs are prone to gathering condensation. You really don't want it dripping back down. Better to put the sheathing in, I don't think it's a massive additional cost to do so.

Cost is minimal. 2 1/2 sheets of ply, and some tar paper.