New Shop With High Moisture Issues

luv2wrench · Mar 18, 2012

just got done putting up a new 75x50 Steel building. There is always alot of moisture in the building and a moldy smell sometimes. The building is super air tight and full concrete and insulation. They footings are the styrofoam forms type and floor is 6 inch concrete with rebar. There is no heat installed yet. Need some ideas on how to get rid of the moisture problem.

Under each vehicle, the concrete is almost pooling water. Tractors are almost wet to the touch at times.

I work everyday and i m only in the shop at night and not everyday. Has a 20x16 door and an entry door. No windows.

I m sure if i was retired and home all day long with door open everday it wouldn"t have this problem.

I plan to add more insulation and finish the inside of the building this spring. A wood stove and overhead radiant heat will be installed summer or fall. Gunna add some windows or some type above the front door to aid in air movement. Certain type of Fans? Ideas on windows??

Do you guys have any sugguestions?? Help!!! Cant stand the musty smell any more. Thanks guys.

dlplost · Mar 18, 2012

Didn't put a vapor barrier under the concrete did ya?
Put a SEALER on the concrete, just clean it good first.

dlplost · Mar 18, 2012

And add some ventilation, big room lots of stagnent air for condensation as the temprature changes from day to night.

luv2wrench · Mar 18, 2012

a Contractor did all the work. is that a norm when doing this work?

plastic goes down first, then sand and rebar? why just under vehicles??

luv2wrench · Mar 18, 2012

This concrete has been down for a year and a half. still wet under or coming through?

dlplost · Mar 18, 2012

"plastic goes down first, then sand and rebar?"
Yes
"why just under vehicles??"
they block what little air flow there is, prevents evaporation.

paul · Mar 18, 2012

I put up a simple shell a few years ago, vented eves, gaps around the sliding doors on each end, etc. Nothing insulated, certainly not at all air tight. 40% concrete floor, 60% gravel.

It was mighty wet in there the first spring, I was quite disappointed. Metal was damp to the touch all over.

Been a lot better the next 2 springs, took a while for the wood and concrete to back out. We had 4 days of fog, very high humidity, and it was just a little humid in there this spring, nothing like that 1st year.

With yours all sealed up tight, you must have a much worse deal. You need those doors open. You need the wind to blow through, move that dampness out.

I think it will be better in following years, and with heat added will make it much better. But - I'm kinda guessing, my building isn't like yours so not a good example I suppose?

--->Paul

dlplost · Mar 18, 2012

probly mostly coming up thru from the ground.
I'd expect condensaton from the air too that's a lot of air in that size building.
We have a high water table here and have the same problem.
Sealing the concrete and get some air flow should help with most of it.

Anonymous-0 · Mar 18, 2012

How old is it??? Could it still be the moisture coming out of the curing concrete?

Dalet · Mar 18, 2012

This time of year the floor is going to be wet from condensation. Keep the doors open for a day or two.

luv2wrench · Mar 18, 2012

I hope it gets better. makes me sick after the 75K it took. Not even working in the shop yet with tools. just storage so far for tractors and trucks and some other "treasurers". Cant image what tools would be like at this point.

The older i get, the better my hind sight is.

gotta be 0/20 by now

luv2wrench · Mar 18, 2012

thank you for your advise. gunna look into sealer. never had much luck with them. I do a ton of mechanic work. chemicals always on the floor and have made other forms of sealer turn into glue and sticky tacky. lots of oil and grease and brake cleaner gunna be all over the floor.

big jt · Mar 18, 2012

Well I have a dehumidifier running year round in my shop.

It does get a little musty in August when I am working around the local show and not spending much time in the shop, and it is high moisture year.

Dehumidifier also helps keep it cooler in the summer.

jt

504 · Mar 18, 2012

Hot air and cold concrete with no air movement means wet. You must get some air moving through that building.

PJH · Mar 18, 2012

My shop is nowhere as large as yours, but it is pretty well insulated. I go out in the morning and it's dry inside. These warm days, I open all the windows and turn on the attic fan as soon as I go out. Pretty soon, the floor is sweating. If I don't turn on that attic fan, it stays dry. Not sure if there's a "fix" for that, unless I move everything to Arizona, and that ain't gonna happen. By the way - my floor has a heavy layer of plastic under it, if that matters to anyone.

Paul

tjdub · Mar 19, 2012

> A wood stove and overhead radiant heat will be installed summer or fall.

There's no moisture problem that a wood stove can't solve. Well, unless your moisture problem is that it's so dry that your sinuses are cracking and bleeding.

Anyway, I think that having no heat this winter is your biggest issue. If you had heat in there you would have been pulling moisture out of the ground under your slab all winter long and wouldn't have the saturation now that the air warmed up.

ss55 · Mar 19, 2012

Where are you located? That happens every year here in Minnesota. The first spring blast of warm, moist air condenses on the surace of anything that is still cold, especially stones, concrete and metal. It's best to either leave buildings closed up to keep the moist air out, or fully open them to warm them above the dewpoint as fast as possible.

This morning my (25 year-old) garage was 51 degrees and dry, the concreete floor temperature was probably still in the 40's. Outside air was mid 60's with a 61 degree dewpoint. As soon as I opended the doors everything inside the garage started sweating because it was all colder than the fresh air's dewpoint.

I left all the doors open, during the day the temperature rose into the mid 70's and the dewpoint stayed at 61. As things in the garage warmed above the dewpoint they dried off again, including the concrete floor. Stepping stones on the north side of the garage were still wet this evening, there was ice over them until Wednesday so that ground is still colder than the dewpoint.

I try to leave tools that I'm not using in their cabinets, drawers and tool boxes to keep them dry in this weather. Any unprotected steel rusts quickly this time of year. Once temperatures equalize above the dewpoint the condensation problems go away.

Dave in Tx · Mar 19, 2012

Just built a 50 x50 this summer. I used radiant barrier insulation and plastic under the floor. Radiant barrier insulation six foot strip around the outside edge under the floor. Air tight also, and never have a moistier problem. We have had lots of rain and huge temp swings this spring. Only problem with mine is it needs to be about an acre in size.

showcrop · Mar 19, 2012

Hard to know much about your situation not knowing what part of the country you are in. My building is 40 x50 x 17 in southern NH and is fairly tight and insulated. ANYTHING of any mass that is cold is going to suck the moisture out of the air when warmer moisture laden air comes along, regardless of ventilation. My tractors in my OPEN unheated barn will drip moisture under those conditions. My enclosed shop is heated all winter to about 38-42 degrees. except for the inner room that stays at about 50. If you raise the temp of that iron by 25 degrees it will be a far more rare passing air mass that will result in condensation. Put a little heat in there and don't bother your self about lack of vapor barrier under the 'crete.

Dachshund · Mar 19, 2012

You need vents in the roof, too, or at least the gable ends. Seal the floor, and get some cross ventilation going. People always forget that "air tight" is never a GOOD thing.

Billy NY · Mar 19, 2012

Probably a good idea to seal the slab, if no vapor barrier, the link below has a bunch of good quality products for concrete, look at the sealants.
Euclid Chemical Company

nateinia · Mar 19, 2012

I agree with 504. If you have asteel frame building for a shop you have no attic. You need constant air moving from a ceiling fan(s) to dry up your condition. Crack open the big door while you are at work this will make a natural draft and help with the problem.

David G · Mar 19, 2012

I do not think adding insulation is prudent until you solve the moisture issue.

Did you put vapor barrier under concrete floor?

JRSutton · Mar 19, 2012

I'm curious whether or not you put a vapor barrier down before pouring concrete?

And when you say insulated, did you do rigid foam sheets under the concrete?

Also wondering how long the concrete has been there.

I agree with what others have said - a wood stove will dry it out no matter how wet it is.
Of course, that only helps during what are usually pretty dry months anyways.

Ventilation is the most important factor. Simply put, you need to get the wet air out, and drier air in.

And of course, with ventilation, you can only get as dry as the outside air allows.

So if you want to be totally dry all the time, you need to get fancy with some kind of climate control system.

MSD · Mar 19, 2012

A new concrete slab that size has a lot moisture in it yet. We run in to the same problem building houses in the fall or winter. Takes a long time to dry it down and with the spring temp. changes, the floor is going to sweat as long as it is cooler than the air temp. Works just like the dehumidifier you run in your house. Warm moist air meets cold surface and condenses on cold surfaces.

donjr · Mar 19, 2012

Built a quonset years ago and it's always sweated, just from moisture in the atmosphere. I put vents in each end, and leave the door cracked a foot or so, and the air moves through so it doesn't sweat so much.

Ferd · Mar 19, 2012

We do a lot of concrete tilt up warehouse buildings and concrete will give off moisture for a log time - a couple years or more. Any building - especially new ones - that are tightly sealed with doors closed and no air movement will have condensation. Roof vents will go a long ways to reducing the problem and any time you can have the big door open will help a lot. For a temporary measure, you may put a couple large portable fans in to circulate the air which will make a big difference.

Texasmark1 · Mar 19, 2012

Absolutely. I always put a vapor barrier between the concrete and dirt and vent the roof. My last shop was 30 x 50 and had two 10' peak vents to get rid of the water. Additonally, I usually insulate the roof to keep condensation from dripping off the purlins on everything in sight. On really humid days where a temp inversion is coming about....interior is cold from the night before, and the incoming air is warmer, a lot of sweating goes on. Keeping the outside air at bay (keeping the big doors closed helps) but by the next day things are nice and dry.

Running a fire in there burns air and a lot of times generates a lot of moisture that the heat drives out of the air; not necessarily good. If you are going to do the fire, vent so that the moist air can escape. Then your heat money will be effective. BTDT

Mark

luv2wrench · Mar 19, 2012

i m located in Nebraska

luv2wrench · Mar 19, 2012

thank you for the link.

New Shop With High Moisture Issues

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