[dneisler]

Ok, I just had me a new workshop built. 30 x 40 x 10 with double bubble insulation. My Problem is...my floors are constantly wet. I want to keep my tools from rusting as well. My mill is nice a shiny and I want to keep it that way. I been told it is due to humidity. I am in NE Texas.

So would a humidifier solve my issues? What should I do?
This is not a full time shop, just evenings and weekends.

[eaglezsoar]

You would need a dehumidifier.
I had a similar problem with my new building and discovered that no vapor barrier was
placed under the building and the ground water was causing the high humidity. I raised my
12' by 20' building so that air could circulate under it. Your building is too large too do that.
Somehow you need to figure out how to ventilate the bottom of the building so that the ground moisture does not penetrate through the floor. If your floor is a concrete slab, then I would see a professional about what you can do too seal it and stop the moisture.

[dneisler]

Yeap it is concrete, about 2 weeks old 4" slab of it. I was told that the slab was cooler than the dew point, and I needed to make sure it was above the dew point and it would stop.

[eaglezsoar]

A dehumidifier would help, but it would probably take multiple units to dehumidify the air
with such a large space. If the ground (concrete) being cooler than the dew point is
truly the problem then I am not sure what can be done aside from insulating the concrete
somehow. One idea that comes to mind would be to put down 1" foam board and plywood over that using tapcons but that would be awfully expensive. I would contact someone in the concrete business and ask what your options are.

Regards!

[tlfamm]

There is no magic available (unless someone has developed a system for pumping expanding foam under the slab). You can:

1. jackhammer the slab and have the job re-done correctly (concrete poured _over_ rigid foam insulation and vapor-barrier)

2. build a false-floor over the slab (with a vapor-barrier and insulation between slab & false floor)

3. Run sufficient dehumidifiers to control the problem. The energy costs of running dehumidifiers will likely add considerably to the electrical bill, though ventilation, even passive ventilation, can help reduce the load & cost of mechanical dehumidification somewhat. There are probably industrial-sized dehumidifier systems that may be more efficient than running multiple household units, but their cost will likely be prohibitive.

Household dehumidifiers sold by big-box stores are very close to complete junk; a better choice is the Santa Fe brand (made in USA, by the way). They are more energy-efficient than most similar-size units, but they are not inexpensive:

http://www.thermastor.com/Santa-Fe/

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It's frustrating to see that even in the 21'st century contractors are still pouring uninsulated (enclosed) concrete slabs in humid locations. It's a simple equation, as old as time: cold surface + moist air = condensation. Enclose the whole system (as in a building), and you've basically created a cloud-chamber - and, I just happen to have one of my own:



My garage slab (poured over 60 years ago) is not insulated either: one humid day I walked in and was horrified to see that my anvil was covered in water-droplets so large that it looked like it had just rained in my shop (droplets on the order of 5/16" diameter).



================================================== ========


Personally, I would build a false-floor: whether it is just plywood over insulation, or plywood over structural members + insulation, would be dictated by the weight of whatever is stored, or brought into the shop. And obviously, vapor-barrier and treated-lumber to be used as necessary - but not overused: no sense exposing humans to the treatment chemicals unnecessarily.

[tlfamm]

eaglezsoar wrote:

>>>>Somehow you need to figure out how to ventilate the bottom of the building so that the ground moisture does not penetrate through the floor. If your floor is a concrete slab, then I would see a professional about what you can do too seal it and stop the moisture.


That prompts me to pose a question to the OP:

Is the major source of moisture in your shop atmospheric, ground-moisture evaporating through the slab, or both?

If ground-moisture plays any role in your problem, then ventilation (active or passive) can help lower the humdity in your shop - but, the presence of significant atmospheric moisture can render ventilation ineffective.

========================


If your situation is anything like mine (I have moisture problems in both my shop and basement), then ground-moisture is a constant problem, while atmospheric moisture is a seasonal problem of finite duration. In my case, ventilation alone can reduce the in-structure moisture significantly - until the atmospheric moisture rises. Then mechanical dehumidification is required (for maybe two or three months out of the year) - as I write this, my Santa Fe dehumidifier is humming away.

To make things _really_ perverse for me, in the winter (New England), atmospheric moisture is locked-up in the frozen ground, and houses have to be _humidified_ to compensate.

========================

Some of the options I mentioned in my previous post can be combined together: EG, a partial false-floor (wherever practical/desirable), combined with mechanical dehumidification - which might include dehumidifier(s) running overnight, replaced with ventilation (passive or active) during the day . The choices are heavily influenced by the source, or sources, of your moisture problem.

[tlfamm]

But, perhaps there is a topping-compound or coating that might offer long-term relief. To be even considered, such must exhibit the following:

1. abrasion-resistance
2. long-term adhesion to the underlying (moist) floor
3. long life-span and/or ease of reapplication
4. effective moisture-barrier


It is doubtful that _anything_ sold in a home-center would qualify (and anything that won't last a decade or more would certainly not interest me personally: who wants yet another maintenance cycle to be bound to, especially for a shop-floor?) A reliable product is not going to be inexpensive, and it may require professional application - possibly including a muriatic-acid etch of the concrete before application. But if such a product exists, it could eliminate the fixed-cost of running mechanical dehumidification/ventilation, or the complexity & drawbacks of a false-floor. (Coatings can't help with atmospheric moisture, however)


I have worked with a product produced by this company:

http://www.conproco.com/selectionchartcrpHOR.htm


The product is so incredible, I bring it up for its own sake, even though it is not a moisture barrier. It is a concrete-topping compound, one that is an order of magnitude more durable than the home-center equivalent:

http://www.conproco.com/ConproOneShot.htm

It is intended to provide a high-grade finish for rough-finished concrete. It dries _rock-hard_ (reminds me of ceramic tile), but can be troweled to a feather-edge. It is expensive: a 35-lb bag (covers 10-12 sq feet to a 1/8" depth) costs about $50. For the intended purpose, it is superb.


I don't see a product on their web-site that jumps out at me - but maybe they have something appropriate for the OP's moisture problem ...

Any coating system that will deliver sufficient, long-lived performance will certainly bring tears to the purchaser's eyes - but a long-term, maintenance-free coating does have its advantages.

----------------------------

The problem under discussion is entirely man-made: 100$ worth of heavy-mil plastic, possibly $300-$400 of extra site-prep, and there would be no moisture problem. Add (a guess), $800-$1000 of rigid-foam insulation, and there would be no condensation problem. That $1500 amount that might have been spent on the front end will very likely not be enough to purchase long-term relief on the back end.

[Sea_en_see]

No A/C? That would solve your humidity problem.

[dneisler]

Well the last two days it has been dry. I am sure mine is not completely curred yet, so I may be jumping the gun some. It has only been down 14 days now.

[pfred2]

Others have fixed their humidity problem by running an oscillating fan to circulate the air. The solution can be as simple as that.

[kawazuki]

Well the last two days it has been dry. I am sure mine is not completely curred yet, so I may be jumping the gun some. It has only been down 14 days now.

I think you've hit the nail on the head there! Average rule of thumb is that concrete dries at the rate of at least 1" / month, obviously without a damp proof membrane below the slab it may never fully dry!
NOTE : DRYs not cures, the two are independent of each other - concrete will cure submerged under water!

[packrat]

No one mentioned roof vents, what kind and how many do you have?

But it will settle down as the slab cures. If it has a vapor barrier between it and ground, the time will take longer to dry out. Every chance you get the doors should be open, to allow air circulation.

cary

[pfred2]

Technically you're not even supposed to walk on a new slab for a month (not that anyone actually waits).

So yeah, you're jumping the gun a bit there.

[pfred2]

Every chance you get the doors should be open, to allow air circulation.

Actually for the highest ultimate concrete strength you should let it cure as slowly as possible. Concrete is is like a crystal and the more it grows the stronger it sets.

Sometimes sprinklers are even used on concrete to keep it wet longer to promote structure in it. Though more often a product is sprayed onto the concrete surface to seal it in a process called "curing". Thats always good overtime there!

[Zygoat]

http://www.homedepot.com/h_d1/N-5yc1...atalogId=10053

that will seal the concrete. they have it in bulk sizes as well to save a little on the cost. if it is coming from the ground that should solve the problem. (wait for it to cure) then you need a de-humidifier. to dry the air. one should work. just has to be the proper size.

bigger pack http://www.homedepot.com/webapp/wcs/...atalogId=10053

"professional" http://www.homedepot.com/webapp/wcs/...atalogId=10053

[pfred2]

Actually this is what should have been done:

http://www.askthebuilder.com/B50_Con...lingTips.shtml

[dneisler]

No, roof vents. I was on a strict budget. Is there something recommended cheap? I was thinking I did't want/need any as I was trying to keep the humidity out.

No one mentioned roof vents, what kind and how many do you have?

But it will settle down as the slab cures. If it has a vapor barrier between it and ground, the time will take longer to dry out. Every chance you get the doors should be open, to allow air circulation.

cary

[ViperTX]

Donald,

Do you have any pics of your building?

Was a vapor barrier put down, before the concrete was poured?

Do you have any drawings of your foundation? Footings?, etc.

Thanks,

Paul

[dneisler]

No. It is just a pole barn. They build the building first, and then poor the concreate. No footings, just fiber reinforced concrete. Guess I got what I paid for. $2750 for a 30 x 40 x 4" slab. I do know they put down 4 loads of premium dirt, 1 load of sand and then they poured the concrete.

[arizonavideo]

For a home shop 4" should be fine. Did they add break lines?

The epoxy coatings would be a nice touch but many sealers could be used to keep it dry inside.

I live in AZ so I don't see any moisture problems, you can put a slab just about anywhere and it will remain dry.