Metal Roof questions... 2019.

[Jstpssng]

^^^
My shed 100 miles north of you is metal on strapping nailed to wooden rafters; everything in it got ruined the first spring I used it due to condensation.

 

[BoylermanCT]

Condensation problems can't just be due to lack of ventilation. I have an open air chicken run with a metal roof on 1x4 purlins on 2x6 rafters, and I frequently get drips in the morning coming down from condensation. I could not add more ventilation if I wanted to - 3 of the 4 walls are completely open with the roof being held up by 4x4 posts.

 

[3Ts]

I'll suggest the metal roof attached directly to purlins and then a 2-3 inch layer of spray foam on the underside. This will 1) eliminate rain from condensation and 2) make the roof a lot quieter during a rain or hail storm. Not sure about the effect on leaks. The spray foam is essentially a polyurethane glue so should glue the screws to the roof and help it seal better.

I have a steel frame pole barn with metal purlins 4' apart and the R panel roofing attached directly to that. The roof inside is about 3" spray foam and I have no condensation and it muffles the rain noise significantly. I do have a 20' porch without the spray foam so I have a comparison. I'd do the spray foam again.

 

[Jstpssng]

^^^^^^
Do you have any problems with mice or ants getting into the spray foam? I had 2” blue styrofoam and the mice destroyed it. Another shed had 1” foam board between the subfloor and plywood on top and the ants go into that. They also destroyed a pile of foam insulation I had stacked up for future use.

 

[tcreeley]

^^^
My shed 100 miles north of you is metal on strapping nailed to wooden rafters; everything in it got ruined the first spring I used it due to condensation.

30 x 30 on gravel, two horses - soffits under eaves 1st and 2nd floor, gable vents both ends, cupola eave vents Metal is on 2x4's on rafters.

The windows are always closed, horse door is always open.

Nothing fancy. We store hay on the 2nd floor. Hay bales stored in the spare stall will mold if left over the winter from being close to the ground moisture. There is never any condensation anywhere in the building. I think it is the ventilation and air flow that prevents condensation.