# My shop has mildew -help



## BamaCummins (Aug 10, 2008)

I built a shop, 24×24, on a concrete slab, fully insulated, with metal on the outside and roof. I don't use all the time, so in the summer sees little use. I use a electric space heater in the winter time.

I guess the summer heat, with no ventilation going, I must be setting up humidity off and on, some tools have rusted and see mold buildup and smell. What is the best way for me to control this, get the right ventilation to prevent? Thought about ventilating with a fan to the outside, but maybe all I need is a dehumidifier.

Thanks


----------



## jonah (May 15, 2009)

If you aren't conditioning the space, you need more ventilation. The tricky part is going to be keeping condensation out of the insulation during periods of temperature change.


----------



## unbob (Mar 10, 2013)

I watched a pro crew cleaning up mold, they used SimpleGreen. I was told not to use bleach.
Mold is really bad for you be sure to clean it up, and do what you have to stop it from growing.


----------



## BamaCummins (Aug 10, 2008)

I wonder what the cost would be just to condition all the time just like your house? Since it is a small space, would need a small unit, costs might not be too bad per month


----------



## BillWhite (Jul 23, 2007)

Didja ever think about a stupid old fan?
Air circulation goes a LONG way.
Bill


----------



## BamaCummins (Aug 10, 2008)

> Didja ever think about a stupid old fan?
> Air circulation goes a LONG way.
> Bill
> 
> ...


----------



## BurlyBob (Mar 13, 2012)

You might consider an epoxy floor coating. After I did mine concrete floor I noticed a very obvious level of humidity in my shop. I chose a light color, yellow. It really added to the brightness of the shop and has made clean up easier. I can't speak to getting rid mold. I just know the epoxy floor coating really reduce the humidity in my garage.


----------



## WhyMe (Feb 15, 2014)

Did you place a vapor barrier below the concrete? I have a small detached garage/shop built years ago and putting down a vapor barrier just wasn't done. So during summer months when needed I run a window AC unit while I'm out there working and the rest of the time there is a dehumidifier running. It's a 70 pint and I have to empty it about once a week. It's amazing how much better it feels with just the dehumidifier running. I don't try to keep it like a desert environment but keep the humidity down to 60-65 percent. Seeing our humidity runs around 80 to 90 percent during the summer 65 percent feels good.


----------



## papadan (Mar 6, 2009)

Put a couple wall vents in at ground level on one end of the building and an exhaust fan at the top middle of the other end.


----------



## BamaCummins (Aug 10, 2008)

Definitely put vapor barrier down. 


> Did you place a vapor barrier below the concrete? I have a small detached garage/shop built years ago and putting down a vapor barrier just wasn t done. So during summer months when needed I run a window AC unit while I m out there working and the rest of the time there is a dehumidifier running. It s a 70 pint and I have to empty it about once a week. It s amazing how much better it feels with just the dehumidifier running. I don t try to keep it like a desert environment but keep the humidity down to 60-65 percent. Seeing our humidity runs around 80 to 90 percent during the summer 65 percent feels good.
> 
> - WhyMe


----------



## Kazooman (Jan 20, 2013)

Too late for a vapor barrier under the pad, but the epoxy coating that was suggested might help a lot. I agree with several others that ventilation is the key here. Get some air moving. If ventilation is not enough to remove the problem, then you will have to go in with the suggested Lysol or bleach treatments to kill off what is currently present.

When I moved in to my present house (built new on spec) I had a bunch of stuff in the basement and then the rains came. While the grading was enough to run the water away from the foundation, a heavy rain would soak in and the water table would rise above the bottoms of the window wells. You could watch then fill up like an aquarium. That led to water in the basement and I had an amazing bloom of mildew. I had some old golf clubs with leather wrapped grips in a bag that was standing upright. Pull a club and see a grip covered with green. Amazing. I had to nuke everything in the basement with Lysol and bleach, but it did cure the problem. I solved the rising water problem with silicone caulk on the windows and later by adding an addition and fixing the problem for good.


----------



## rustfever (May 3, 2009)

A complete vapor barrier under the concrete is necessary. An added epoxy 'vapor barrier' on top of the concrete is a waste of money and effort. Try to move more air using vents low on the walls and in the ceiling/roof.


----------



## Kazooman (Jan 20, 2013)

> A complete vapor barrier under the concrete is necessary. An added epoxy vapor barrier on top of the concrete is a waste of money and effort. Try to move more air using vents low on the walls and in the ceiling/roof.
> 
> - rustfever


Just curious, out of a total lack of in depth knowledge on the subject. What is the difference, in the final result, of a vapor barrier under the concrete pad and an impermeable vapor barrier on top of the concrete pad? Epoxy would shut down the moisture 100%. The only difference I can see, at first glance, is some effect on the concrete itself. No moisture above the pad with a good vapor barrier versus no moisture above the pad with an epoxy coating. Is there a difference?


----------



## builtinbkyn (Oct 29, 2015)

The vapor barrier is a heck of a lot cheaper than the epoxy coating. Also easier to apply. Will the epoxy work? Sure as long as the concrete stays as one piece. If it develops cracks, then there's the potential for moisture penetration. The cracks can be sealed as long as there's nothing concealing them.


----------



## rustfever (May 3, 2009)

A concrete vapor barrier is a system. It reguires a layer of drain rock, vapor barrier [ie: Visqueen or similar], and then a layer of sand. Over which the concrete is carefully placed. If moisture is allowed to migrate into the concrete, then all is lost. Epoxy may help for a few days/weeks/month, but will fail. Money lost.

I spent 40 years as a professional concrete contractor, dealing with all level of high-teck concrete for business and industry. I have been paid mega $$ in the restoration of improperly place concrete and vapor barriers.

Pay me now or pay me X-times later.


----------



## IHRedRules (May 11, 2014)

Once you clean up the mold, use a simple dehumidifier and keep an eye on the humidity. I bet that will fix your problem.


----------



## BamaCummins (Aug 10, 2008)

Thanks for all the ideas, now another one. It looks like if I went with a right sized dehumidifier, I'm out about $250. If I installed a mini-ductless ac unit, about $700-900. 2 1/2 times the costs, but I get a conditioned space year round. Never considered before because I'm not out there every day, but knowing this is my goal down the road, maybe this is money better spent? Any thoughts?


----------



## kelvancra (May 4, 2010)

Don't forget, there are some very good concrete sealers out there and they are a fraction as expensive as epoxy.

Now that I moved from the Northwet to the opposite side of the hills (I-5 Corridor to North Central Washington), moisture is no longer an issue. I still have my Sears dehumidifier. I allows me to set it to different levels and I can either empty the container or run a hose. It's a humidity grabbing beast and worth a consideration.

I made the mistake of not drying my car well enough once, while living on the coast. The mildew smell popped up pretty quick. However, a single visit to Eastern Washington on a hot summer day solved the problem. Apparently, having the windows rolled up cooked the contents of the car well enough the smell left and never came back.

Now I know to run the dehumidifier, if I have to shampoo the carpet floors of a rig.


----------



## kelvancra (May 4, 2010)

All my ramblings, above, aside, I'd vote for making the place comfortable. It's kind of like buying a really good saw, after making do with an under powered, low accuracy homeowner version. You find yourself jumping in to projects that, before, seemed daunting without a second thought.


----------



## FancyShoes (Aug 31, 2014)

I used a dehumidifier and it helped get rid of the mold problem. But yes a small ac system will do the same, and probably use slightly more electricity, so you would not being paying much more over the long term adding a ac system.


----------



## sawdustdad (Dec 23, 2015)

A window air conditioner will cost about the same as a dehumidifier to run, so might as well cool the space. Both will remove moisture. The dehumidifier dumps the heat into the room, the air conditioner dumps the heat outside.


----------



## Ocelot (Mar 6, 2011)

Also, don't try to dry green lumber in your shop.

(Sorry, I know it's an old thread but I just was reading it and had to say that. I had a friend you put a lot of green lumber in his basement and had a problem.)


----------



## ArtMann (Mar 1, 2016)

Based on the original poster's chosen name, I suspect I live in the same environment. I had the same problem in my new well insulated 24 X 36 shop with concrete floor. The problem went away when I installed air conditioning. Even with the thermostat set at 80 in the summer, it keeps the humidity low enough so it isn't a problem.


----------



## BamaCummins (Aug 10, 2008)

Problem solved, I put in a mini split ac unit, and absolutely love it, should have done it years ago, and doesn't costs that much to run. bought the unit for $500, so good all around.


----------



## EricFai (Sep 30, 2018)

The concrete will wick up the moisture in the ground and as it moves through the concrete it will cause an expoxy coating to blister.

Best bet is to run a dehumidifier, or ensure that you have a cross ventalation for the building.

I am planning on a shop with a evaluated floor, basically a deck with avantech on the floor. The plans are to insulate the floor. But I will have to put in a vapor barrier down first with about 2" of gravel. Sides will be open so I will have a cross ventalation under the floor.


----------

