Moisture from condensation can be a major issue in initially poorly thought out pole barns.
Reader MATT in SHAKOPEE writes:
“Hi. I am having issues with moisture in my pole barn. It is getting to the point that mold is starting to show up on the walls and cement floor. The barn is about 28 x 36 with 12 foot walls. It has a service door and two 10 foot over head doors and 4 windows on the south wall. The ceiling is tinned, insulated and has a vapor barrier. The floor is cemented and I am unsure if the floor has a vapor barrier. The walls are not insulated or tinned.
The barn is used for storage right now cars, mowers, tractor, etc. The barn is unheated and sometimes the doors stay shut for one to two weeks. We have gone through and cleaned what seems to be mold off the walls but are unsure on how to stop the moisture issue. Wonder if some kind of exhaust fan would help? Or if you have any suggestions? Any help would be greatly appreciated.”
Mike the Pole Barn Guru writes:
I’d start with trying to eliminate moisture source. If you leave a wrench lying upon your building’s concrete floor for a few days and return and a dark spot appears below where the wrench was placed, your building has no under slab vapor barrier. If this occurs, use a good concrete sealant across floor. This in itself might resolve problems – watch the steel wall siding insides and see if they stay dry after sealing.
If this does not resolve problems, then you need ventilation. I will surmise your building does not have enclosed vented soffits and a vented ridge. Can’t go back and correct lack of overhang issues now, but you can add gable vents – a minimum of 242 square inches net free ventilation area in each endwall with vents located in top half of each gable.
Location of your building should also be examined. If soil around building exhibits signs of being moist, you need to make sure grade will allow water to drain away from building. It may be necessary to trench around building and add a drainage system to move water away from your building. Gutters should drain water sufficiently distant from building as well.
If nothing else works, here’s how to determine power ventilation requirements: https://www.hansenpolebuildings.com/2018/07/my-pole-barn-needs-ventilation/.