Moisture problem in new shop!

[iublue]

Was the concrete ever sealed?

No. I thought that was mostly to prevent the concrete getting stained by oil, etc.
Maybe they make a sealer that would also act as a moisture barrier.
That is if the moisture is coming through the concrete!

[Roly]

Rust -oleum makes a moisture sealant for concrete.  I have no idea how good it works.   https://www.rustoleum.com/product-catalo...ing-sealer.   It goes into the concrete and seals not just on top.   Used under epoxy coatings.   Roly

[Admiral]

That is if the moisture is coming through the concrete!

I think that's the only rational source.  The plastic idea is an excellent suggestion and will likely tell the origin tale.  Then becomes the quesiton of sealing the slab, expoxy may be that answer but who knows, you have to research that a bit.

Otherwise, I feel for your frustration, good luck with finding a solution.

[MNice]

Is the heater vented? If not, that’s a big part of the problem. I run a ceiling fan 24/7, live in MN and have zero problem in my 24x24 shop heated with vented gas unit heater.

[Cabinet Monkey]

Who designed / specified this shop build ?

Was it inspected by an authority or private engineer ?

You do know that water vapor is an entirely different animal from water. Right ???

Your issue is your slab, plain and simple.    Propane ain’t helping, and your dehumidifier is clearly undersized for  your volume.  Along the lines of big game hunting with a squirtgun.

Do the test, and start looking for companies that apply commercial vapor barriers on floors.  Your issue is not all that unique.

[iublue]

Is the heater vented?  If not, that’s a big part of the problem. I run a ceiling fan 24/7, live in MN and have zero problem in my 24x24 shop heated with vented  gas unit heater.

I heat and cool with a mini-split or AKA an air source heat pump.
No venting required.

Thanks for the reply

[iublue]

Who designed / specified this shop build ?

Was it inspected by an authority or private engineer ?

You do know that water vapor is an entirely different animal from water. Right ???

Your issue is your slab, plain and simple.    Propane ain’t helping, and your dehumidifier is clearly undersized for  your volume.  Along the lines of big game hunting with a squirtgun.

Do the test, and start looking for companies that apply commercial vapor barriers on floors.  Your issue is not all that unique.

The metal building people designed the building. 

No inspection here after the foundation.

Obviously water and water vapor act differently but even if there is significant water vapor under the slab it would need a certain amount of vapor pressure to force it to migrate through the slab.  It is hard for me to see why there would be vapor pressure under the slab.

I will do the test and it will probably indicate that the slab is the problem.  I could seal some of the slab but I am not going to move all the benches and equipment just to seal the concrete.

I have not used LP for over a year.  I have a mini-split for AC and heat.  Even with the mini-split running during last summer, the RH did not get under 50%, IIRC. Maybe using foam concrete forms for the stem walls in the foundation plays a factor. I will probably never know the exact cause!

Thanks for the response.

[iublue]

I think that's the only rational source.  The plastic idea is an excellent suggestion and will likely tell the origin tale.  Then becomes the quesiton of sealing the slab, expoxy may be that answer but who knows, you have to research that a bit.

Otherwise, I feel for your frustration, good luck with finding a solution.

Thanks,

I will post the outcome of my test.

[Alan S]

Water doesn't need applied pressure to go slowly through concrete.  Capillary action drives it through -- the same thing that takes water from the ground and brings it to the tops of the trees.

The plastic test sounds a good idea.  I hope an epoxy coating does the trick.

[Bach1750]

You might want to try drilling a few 1" diameter holes at grade on the low side of your foundation.  If your area has a high water table, that could force water within your foundation upward toward your slab... like an upside down tub.  If you provide an outlet for it, a kind of relief valve, that might help with your problem.  

Sounds frustrating, hope you can work it out.