How can I get rid of the smell of damp concrete in my studio?

I have been working without success on the smell in my 12' x 14' studio for 5 months, so I really hope someone can help me. I can put my nose right up to the walls and the ceiling and the outlets and not smell anything. But when I put my nose right to the floor I smell the dank, musty, yucky smell of damp, dank concrete. The place reeks of it, I can't work in it. I smelled it last October when I was looking to buy the house, I told the inspector about it but he could not smell anything. Everyone can smell something when they open the door, some people can tolerate it but I can't. As soon as you open the door it just overwhelms you.

What I have done so far:

1. Had two peg board walls removed and replaced with chipboard, because that was what the other walls were made of. I had assumed at that time that the smell was mold coming from the pegboard. At that time I looked at the insulation inside the studs and it was fine. It smelled so good with that new chip board up that I thought the problem had been solved.
2. In preparation for painting I caulked the ceiling, around the windows, and up against the floors where it meets the walls.
3. Painted 3 coats of Kills primer on all the walls.
4. Painted 2 coats of very good quality semi-gloss paint on all the walls.
5. I scraped off all of the existing paint that was on the floor. It was peeling in places which is what led me to think the smell was coming from the concrete.
6. Washed the floor with a de-greaser.
7. Washed the floor with sulphuric acid, and rinsed it about 30 times.
8. Painted the floor with 3 coats of special paint made for concrete basements to act as a waterproofer.
9. Painted 2 coats of sealer on top.
10. I called the previous owner who confirmed that the studio's monolithic slab was poured without a vapor barrier because code didn't call for it, because no one was going to spend the night there or live in it. He never noticed the smell.
11. In all this time I have run the A/C non-stop, with the windows open, with the windows closed, with no effect. I have even run the heater for a few days. I have cleaned the A/C over and over, there is nothing to clean and the smell is not coming from there.

Is there anything I can put on the floor to effectively seal the smell from getting into the air? Why didn't all those coats of concrete paint and sealer do it?

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Ninzerbean (author) 1 year ago

Update as of 2016: To anyone else with this problem I should say that with the help of canusksgirl and Spycor Building Products the problem was solved. I bought the more expensive of the two products Spycor sells for this sort of thing and followed their directions. I put a fake (but it fools everyone) distressed wood floor that comes on a 12' wide roll over all of the Spycor stuff (plastic, dimpled product, plywood etc) and the smell is gone, it was gone as soon as I installed the Spycor product. It's been over 3 years now and I should have come back before now and say that the problem has been solved. I really love walking through the door now, I never take for granted that it smells wonderful.

Good to hear!

heating245 years ago
I would agree with canucksgirl. Dehumidfier may help eliminate the smell on your floor.
canucksgirl5 years ago
If your dimensions are accurate (which I assume they are), then the previous owner should have obtained a permit to build this (as any "accessory structure" over 120 sq feet requires a permit in Jasper County). I would be very surprised if a vapor barrier was not required for the concrete slab, for 3 reasons. The first, is that its usually recommended for a monolithic slab. The second, it appears that your town is in the "FEMA Floodplain" which may or may not impose additional rules, and lastly is due to the type of soil you have (which is listed as sandy loam over clay loam, that has poor drainage).

Without a vapor barrier the concrete is sitting directly on crushed rock (if properly installed), and when the water table increases, the moisture soaks into the concrete which is more porous than the clay base. If there's no crushed rock, the water issue would be undoubtably worse. Sealing the concrete can help in some cases, but it will never solve a water drainage issue.

As far as the regulations, your county does have some pretty strict rules, so whether you investigate that, its up to you, but any further work is suppose to require a permit.

Some options you have is to dig a trench about 3-4 feet down around the perimeter, add crushed rock and PVC drainage pipe (wrapped in a filter sock to prevent clogging) with a "T" connection leading downgrade and as far away from the building as you can. Cover the pipe with more crushed rock and cover with soil, so that any excess water is diverted away from the slab.

A gutter system around the roofline would also be a good idea with a downspout carrying the water downgrade and far enough away.

Also adding a roof vent (with or without an exhaust fan) would help, especially if you notice the inside gets hotter and more humid than outside. The musty smell can easily be found in structures with poor ventilation. Additionally, running a dehumidifier can help.

As far as the smell, you can clean with a vinegar/water solution (1:5) as it neutralizes odors, (or sprinkle damp areas with baking soda and sweep up the next day), but the best method is to control the source of the problem which I believe is a drainage issue coupled with a lack of a vapor barrier.
Ninzerbean (author)  canucksgirl5 years ago
I'm in Beaufort County actually, the line between Jasper and Beaufort is really ziggy. But no matter, there is a thing about not having to put a vapor barrier down if the space is not for living - think garage. The rules, if they were followed or not is moot at this point. I bought the house as is. I had it inspected. I thought I could deal with the smell by taking down the peg board. I was wrong.

I am one of those people who never turns the A/C off, so a roof vent will not help. I have to find a way to block the smell from the source.

There is nothing to clean either, the floor was so clean and properly prepared before I put the concrete waterproofing paint down you could have licked it. Now it is really beautiful to look at, the 2 coats of sealer make it so shiny, but there is nothing to clean, there is no way to clean the smell away. It is absorbing the damp from the ground, the smell permeates the coats of paint and sealer.

The trench idea won't help because I still have the whole area under the house that the slab is using to absorb the damp and release it into the air in the studio.

Water from above is not the problem either, we had a long dry spell this summer, the ground on the surface was like sand, dry sand. but underneath it is damp.

I thought if anyone was going to be able to solve this it would be you, and I thank you for trying, and it is obvious you have done a good amount of work on my behalf, but none of your ideas will work. I have great ventilation - 3 windows and a ceiling fan, and an air conditioner. Even if I leave the door open too with the windows open, the ceiling fan going, the a/c going, you can't escape the overwhelming smell when you step over the threshold.
Sorry for the late reply...

The only other option I can suggest is to create a thermal break and vapor barrier above the slab. You can do this with a 'dimpled plastic (polyethylene) membrane'. Its basically high density polyethylene with dimples on one side and a "cupped" surface on the other. It IS completely waterproof (when installed correctly) AND completely air tight (meaning no water vapor and odors can pass through). It differs from a simple polyethylene sheet in that the dimples create insulating air pockets. The vapor pressure is also equalized under the membrane (and above), eliminating condensation and slows (but won't stop) water seepage through the slab.

You would install the product directly (dimple side down) over the concrete (no glue or fasteners) as close to the walls as possible, sealing the seams with an approved moisture proof tape, and using sealant around the perimeter (some suggest silicone, some suggest low expanding spray foam). Once the membrane is installed and sealed you have a few flooring choices. Laminates can be installed directly over the membrane (with the recommended underlayment). Vinyl flooring will require a layer of plywood, but you'd need to use tongue and grove because you cannot use screws or nails (as it will create holes in the membrane). Tile (like ceramic) can be installed, but you'd have to remove all of the coating you put on the concrete, because the membrane used with tile is applied with thinset mortar directly to the concrete (and likely won't adhere to your coating). A cheaper method is to lay T & G over the membrane and just paint the plywood.

Overall the DIY installation is easy, its relatively fast to do, it isn't super expensive and if you were to have some major water issues in the future, everything could easily be pulled up and the membrane reused after the problem was solved. IMO, its your next best option to a perimeter drainage (weeping) system and installing gutters and downspouts.
Ninzerbean (author)  canucksgirl5 years ago
You are the best you know. Why isn't there the option any longer of saying which is the best answer? Did I post this in the wrong area in the forums? I hardly ever go here. Anyway...

When you say to lay T & G over the membrane and paint the plywood what do you mean? Why would I paint the plywood? Does there have to be plywood under the T & G? Can't the T &G go right over the membrane?

I have had two floors in the main house done with engineered T & G wood since I moved here and it was quite expensive compared to laminate. It looks great though. A builder friend and I thought about that, but before we did anything I wanted to hear what the Instructables community would say.

Oh Oh! I think I know what you mean now - you are saying to use a T & G plywood as my floor over the membrane! Oh I get it. But because I am getting old and decrepit my feet hurt a lot. I don't want to stand on anything hard any more, so could I put down the T & G plywood and put a carpet pad and carpet down? I have one bedroom left to get rid of the carpet in and I could use that carpet.
Thank you a thousand thank times.
You are too kind. The patch wasn't necessary, but I thank you for it. That was very nice of you. :-) As for the "best answer" option it is only in the Q & A section. The regular "community forum" pages don't have answer options (I guess because not every post is a question?)

So yes, hehe, I did mean T & G plywood over the membrane (but I only mentioned painting it as a cost effective option for your studio, versus adding more flooring expenses). Carpet and padding can most certainly be installed over the membrane, HOWEVER, carpet should be stretched and secured with tack strips which requires plywood between the membrane and the carpeting.

If you refer to the image I added you'll see what the membrane actually looks like. Since you cannot put holes into the membrane (with nails or screws), the only way a tack strip can be installed is onto T & G plywood.

If you install the carpet without a stretcher and tack strips, it will leave the carpet susceptible to wrinkling and movement (as the stretcher and tack strips are meant to keep the carpet tight to the subfloor); and if you use tack strips on the concrete or through the membrane, it will no longer be air or watertight (thus defeating the whole point of this).

You should also notice the vapor barrier (from the wall) in the image. When you put the manufacture recommended sealer around the perimeter (for the membrane), you do so below the vapor barrier sheet. Then the vapor barrier goes on top of the membrane. Its best to use the membrane sealing tape to secure the vapor barrier on top as well, as it will improve the air and water tightness of the seal. For your studio (where no barrier appears to be), you should consider adding it in the same fashion and seal it to the base of the walls. That way if any moisture (or vapor) is traveling up the sides, it will NOT permeate the room. The additional cost would be minimal as the amount you need to cover the concrete sides isn't very much, but is worth the effort.

Finally, before any installation, climatize the materials in the room they will be installed for about 24 hours. This ensures that everything has adjusted to the room and you'll be less likely to have any material expansion/contraction issues. For all rolled products, you may also want to unroll them (if possible) during this process to prevent curling of the materials when you try and make them flat.
Ninzerbean (author)  canucksgirl5 years ago
I went to Lowe's but they did not have the polyethylene liner with the dimples. They actually thought I meant bubble wrap. I bought some 6 mill plastic. I am going to try making a shell of sorts in the room, sealed up the wall a few inches. I am going to use Duct tape because I checked out the tape they had for this purpose at Lowes and I know that after you let Duct tape sit for 12 -24 hours it is very tight. I use it for making my silk screens. The tape at Lowes was not very sticky feeling. I can't let ANY air escape. I am going to try this as soon as I can get some strong guys to help me move a huge chest of 50 drawers from an old hardware store that is in the studio that I cannot move my self. Even after I take out the 50 bins in it it is beyond heavy.

Then, if that has helped a good amount, I will go ahead with the plywood, the T &G. It sure does not look as nice as the stuff in that photo above. But at least they have it. I have to buy it in 4 x 8 sheets. I wish there was an alternative. Such as planks but then we are talking a lot of money for real wood and that goes back to my feet - I can't stand around on hardwood. It's as hard as concrete to me.

I think you may be thinking I am doing this backwards - I sort of am. I figure that if the 6 mill plastic makes a difference then I can do without special ordering the dimpled material. I won't be starting this project this week so if you think it is really really wrong you have plenty of time to stop me.

Unlike a basement where this application is often used, the studio does not have concrete walls. It is just a building that sits on a monolithic slab of concrete. Any you would think that when I put my nose up to the outlet covers I would be smelling the wet concrete smell from the area inside the walls where my special paint and sealer could not reach - but oddly I can not. That is a puzzle to me.

Thank you 1,000 more times.
First off, it sounds like you talked to a clueless employee at Lowe's… According to one of the major manufacturers (DELTA) for the dimpled polyethylene membrane, DELTA-FL can be ordered from any Lowe's store in South Carolina. Alternatively, its also available from the SPYCOR Building Products website (I think their prices will be better than Lowe's).

Now, should you use 6 mil poly on your floor? Probably not.
Since I don't want to leave you confused let me explain a few things…

Ground water is under hydrostatic pressure and moves toward lower pressure areas (like the air above ground). Water vapor works in the same way in that its attracted to drier areas just like warmer air wants to travel toward colder air. If there was a lot of water in the ground you would eventually see it on the slab (because there's no barrier to stop it), but in this case its just a constant movement of water vapor that's evaporating. Over time this process has caused odors because the concrete slab doesn't get a chance to dry out and its probably caused some mold or organism growth within the pores of the slab.

If you were to put the poly sheeting on the concrete slab you would reduce the water vapor from passing through (which is good), but when that water is unable to evaporate, condensation occurs and eventually mold and fungi grows and you get an even worse smell (not good). The use of your AC is also affecting this process in that the warmer water vapor in the ground is attracted to the colder air above because there is nothing to insulate the two.

With the dimpled poly membrane, only part of the surface sits on the concrete, leaving an air space between the flooring above and the concrete slab below. The air in between is insulating the two temperatures, thus stopping the formation of condensation. The water vapor is also able to dissipate in this air pocket by moving laterally and when there's an excess, it can "breathe" through the concrete on the perimeter walls. (This is also why you want to add a barrier to the concrete sides, and why there should always be a barrier between the wood framing and the concrete). In normal concrete slab installations, the vapor barrier and the crushed rock basically work the same way.

The only method that I know of to use the 6 mil poly would be to install rigid foam insulation above it and then the T & G plywood and then the carpet and padding. The rigid foam would have to have a good R-Value to ensure that its insulating enough to reduce problems in the slab and you would have to spray foam the perimeter and tape all joints to ensure a good seal. This method would work, but isn't ideal. It may also end up being too thick of an installation for your floor, which would force you to adjust your door height if there is not enough clearance at the bottom (so measure everything out first!)

In either case, I would advise you not to put holes in the poly sheet or in the membrane with any installation methods that suggest using TapCon (or other) Screws to secure the T & G Plywood. Although I would recommend the Delta-FL, they do suggest screws with silicone on the plywood, but in my opinion, its a huge mistake, because it lowers the effectiveness of the barrier by relying on the silicone. I suspect that its recommended more for below ground installations and in climates with colder winters and warmer inside temperatures to prevent any expansion/contraction of the plywood (but they don't specify this). So to avoid any potential problems, it would be best to leave a small perimeter gap to allow for expansion. This shouldn't have any effect on the carpeting and would still give you ample room to use tack strips and to finish off the edging with some baseboard moldings. In your studio, it would be best to use a plastic molding (versus wood or MDF) as you can install it to the concrete sides with the correct adhesive. These moldings not only look exactly the same, but they tend to be a lot cheaper.
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