How can I set up a mildew-free workout space in my unfinished basement?

February 13, 2012 8:32 PM

I want to use my unfinished basement as a workout space and have laid down some interlocking foam tiles on the bare concrete floor. However, the floor under the tiles has started showing mildew after a few weeks in place. How can I set up a comfortable workout space in a typically humid but not wet basement without having to lift the tiles every couple of months to scrub out the mildew?

* My workout space is about 8 feet by 8 feet, with enough space for floor exercises at one end and a weight bench at the other end of the tiles. I could keep the tiles under the bench all the time (removing them as needed for cleaning) and lay down the free tiles only when I work out. Or I could just give up on tiles beneath the bench, although that would make the transitions for some exercises awkward.

* Would laying down a plastic sheet between floor and tiles help or hurt? I have seen plastic bags left on the floor for a long period also start showing mildew.

* I cannot afford to put in any permanent flooring yet. I need a relatively simple and cheap solution. If the only real solution is real flooring, I guess I'm scrubbing the floor periodically. (I've removed other areas of mildew with cleaner, bleach and elbow grease.)

posted by wexford_arts to Home & Garden (13 answers total)

Dehumidifier, perhaps?
posted by Madamina at 8:35 PM on February 13, 2012

You have a perfectly typical condition which is moisture coming up through the floor that condenses on any cool surface above it. If you are getting mildew it also indicates that there is some sort of minute organic material presence on either the slab or the surface above it, or getting in from the edges.

Pretty much anything you do will be dealing with this issue. Particularly when you go to put in permanent flooring you'll want to be quite aware of it. In theory you could scrub the area with a very light chlorox mix (5%) and then put down a fresh clean heavy plastic sheet and tape the edges. You'll still get moisture underneath, but if you can keep the area free of contamination it should just stay as moisture and be controlled by the plastic.

That's probably the best you can do and it is in a way a half measure as you are trying to use a thin piece of plastic against the force of water.

As an aside, a dehumidifier won't address this situation as it deals with latent moisture in the air, and you are dealing with diffusion through the slab. Additionally, anything insulating the floor (like that foam or future flooring) is actually accelerating the problem by slightly lowering the floor surface temperature and allowing more condensation.
posted by meinvt at 8:47 PM on February 13, 2012

I assume it's mildewing because moisture is occasionally seeping up through the concrete? Maybe you could seal the floor (or just that patch of floor?) with a paint designed for the purpose.
posted by hattifattener at 8:50 PM on February 13, 2012

Use a product like dri-core to allow your floor to dry and not trap humidity beneath your mats. It's around $1.75 a square foot which may be out of your price range.
posted by Mitheral at 9:04 PM on February 13, 2012

ok, its a lot of work but a long term solution will be to build a 'deck' frame out of treated wood, than work out on top of that. Build it like you would a mudsill on top of foundation. Put down a vapor barrier between the wood perimeter and joists and the concrete (only, not the entire area covered by the deck-there should only be the vapor barrier directly between the concrete and wood contact). Put in a full perimeter than joists about every 16" On center. Than put in either trex or cedar decking over that. You want to leave a gap between the slats on the deck so the area underneath can breathe and you don't get trapped moisture there. It will probably last a good long while (like 10 or 15 years). I would use 2x4 of treated lumber for the everything in contact with the floor and than cedar decking on top for your workout platform. Mostly because cedar smells good and that will help with the musty gym smell. Trex (or some kind of composite decking material) will last longer and be stronger but it will be slick when you sweat on it or moisture condenses and it won't have any mildew fighting properties like cedar or redwood will. this won't be cheap but it will be cool and you will get a decent workout just building it(my workout these days is an hour or two everyday after work framing in and building a shower)
posted by bartonlong at 9:48 PM on February 13, 2012

The easiest way that occurs to me is to cut slits in some of your pads so that you can slide them under your bench without having to pick it up, and then roll up, pick up, or lean the pads against a wall when you are not working out.

If you're using those thin 'jigsaw' type mats that interlock you could use gaffer tape to secure them together so instead of picking up a bunch of individual tiles you're only picking up 2-4 larger 'pads.'
posted by Th!nk at 12:36 AM on February 14, 2012

bartonlong has the right approach there, I believe. You need to get some space between the concrete and what's on top of it.
posted by RustyBrooks at 7:53 AM on February 14, 2012

You could construct a pulley system to raise the pads to the ceiling when you're not working out. You would probably attach the pads together to form one large pad.
posted by jander03 at 8:10 AM on February 14, 2012

You need airflow. You could build a floating floor as suggested but you could also try commercial kitchen flooring like these rubber mats. If you need to lay on the floor to do exercises just roll out maybe a closed-cell foam pad and yoga mat over the top and put it away after.
posted by amanda at 8:59 AM on February 14, 2012

Dricore is what you're looking for. You could easily assemble a small subfloor area on top of which you can then put your foam tiles. Easy and relatively affordable. I've used DRIcore in my basement and it works great.
posted by bluefrog at 9:26 AM on February 14, 2012

Lots of great answers, thanks! I won't be using them all, but here's how I will probably rank my choices:

1) Immediate and free: Cleaning up, then moving the tiles back in only when needed is pretty straightforward. I can do that now.

2) Short term: I can try a heavy sheet of plastic as a vapor barrier, but OTOH, this may not be enough to guard against moisture between it and the concrete, even if the mildew is warded off.

2) Medium term: I'll check prices of a rubber kitchen mat (or similar interlocking tiles) as well as DRIcore . The DRIcore is about $7 per sheet (regular price) and it may go on sale, so while it's pricier than my ideal solution, it's still not too bad, and it could be the first step to properly finishing my basement.

QUESTION about the rubber mat: The rubber kitchen mat is probably cheaper, but could it still allow some moisture to waft up between openings / seep through the rubber to my foam tiles so that I may still get mildew?

QUESTION about DRIcore : The installation instructions require about 1/4 inch clearance from walls and obstacles. I'm presuming that because it isn't nailed down or abutted to the walls, it would work just fine as a freestanding surface (maybe 6' x 8') in my basement. It shouldn't shift around after being properly levelled and shimmed (where needed), right?

bartonlong, thanks for the detailed answer, but I don't think that I have the expertise to create a custom platform like that. It's a great description, though, so hopefully someone else will be able to use that for their basement.
posted by wexford_arts at 4:26 PM on February 14, 2012

Dricore is a floating floor product which means you need that 1/4" of space to allow the floor to expand without buckling. It might move around a bit if placed away from walls, nothing a bit of duct tape or a few dabs of silicone wouldn't fix.
posted by Mitheral at 12:40 PM on February 16, 2012

Thanks, Mitheral!
posted by wexford_arts at 11:47 PM on February 19, 2012