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Question DetailsAsked on 8/21/2013

What type of contractor should I hire for waterproofing a 3rd car garage floor for a home gym?

We went all out and made a home gym in our third car garage, unfortunately we did NOT waterproof the floor before laying down foam exercise mats and moisture puddled underneath then "mold" came up between the cracks. After saving up and purchasing new mats, we tore up the old mats, treated the floor with Drylok (after the necessary cleaning and prepping) and put the new flooring down. Apparently we didn't do a good enough job and we have the mold and moisture back again! I'm thinking we need to hire someone to remove the Drylok we put down and treat the floor but what kind of contractor does that kind of work? And what kind of work is it exactly - waterproofing?

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Voted Best Answer

Waterproofing is the category, and your case as it stands now is hopeless. Hate to be the bearer of bad news, but if your floor is that wet, you are not going to use waterprooofing compounds to solve the moisture problem enough to be able to lay waterproof mats on it and not have mold problems. Good luck - I think the only guaranteed solution to absolutely avoid the problem, which would be very pricey, would be either a new slab with built-in plastic full positive vapor barrier, or a false floor over the concrete with power ventilated airspace under it.

A good portion of your problem might well be condensation of air moisture at the cold concrete interface, in addition to moisture coming up through the slab, so while an impervious waterproofing plastic sheet over the slab and bonded to the walls and a dehumidifier in the room running continually MIGHT make it satisfactory, I really do not think you will ever be able to get rid of the moisture problem that way.

To avoid ridiculous cost, I would look at how to get around the problem - a dehumidifier or ventilation fan at floor level (like a 20" portable fan) certainly to start with, but if in a garage you are having a lot of air changes with the outside air, so during humid days you will still have the condensation problem. I do not know what your exercise mats look like, but if you can put a few wood pallets in a corner or build a wood frame that holds them 6 inches or so off the floor and allows airflow all around when not in use, then for an hour or two exercise period or so I don't think you would have a problem, being sure to store the mats so what was the floor side is up while in storage, to air.

If these are not just a few gymnastics-type roll out mats that can be be easily rolled up after every use, then I can only see a few other alternatives which MIGHT work - from those I have the least confidence in to the most - just happened to fallthat way:

1) spray a mildewcide on the slab and lay down a heavy duty vapor barrier like 8-12 mil visqueen fastened with batten boards all around the edge of the slab and lay the mats over that, though you will still get water between the visqueen and slab and might get mold over time,

2) lay out a gym floor mat (used to protect wood basketball floors during gym period) under your mats, and take it up and dry it as often as possible, or move it around every few days if it only covers a portion of your 3rd car slab at a time, or

3) One quick and dirty solution - buy a box of 6 mil visqueen and lay it down under the mats, then say weekly or so take it all up and move it to a different area (if there is room) to let the first area dry, then toss it and bleach scrub the floor when it starts showing mold, though that is not a very pro-active solution.

4) get some soft plastic (not fabric) mesh geotextile drainage fabric (also called geoweb or geomesh) like this at your building supply store or geotextile jobber -

There are also laminate and carpet flooring underlayments that look like this - you would need one that is soft so it does not poke holes in your mats, is open in all directions or even better with a solid vapor barrier on the top, so the moisture under the mats can evaporate into the surrounding room - keep open to air on all 4 sides. Make sure it is plastic with no fibers to grow mold or foam to hold moisture. It might help to run a fan in the area, maybe on a timer, for a few hours a day directed at the web/mat layer to promote evaporation.

5) I don't know how big an area you have mat covered, but you could easily build an elevated exercise platform using treated wood and exterior grade or roof sheathing plywood or particle board, then dehumidify or ventilate the area and, if necessary, run a fan on a timer (preferably an every hour one rather than one a day) to ventilate the area under the false floor. If you don't care about looks, you could whip up a quick one of treated 2x4's and plywood - the key is provide airspace, so something like a 2x4 grid on edge with a grid of 2x4's laying flat over the top or dadoed into the base ones would leave air space all ways and take the springiness out of the overlying 1/2" plywood, otherwise one layer of 2x4's laying flat and covered with 3/4" plywood, then your mats. For additional moisture protection for the mats you could put a layer of 6 mill or heavier visqueen over the 2x4's before you put on the plywood. For normal mat exercise 2' spacing should be good, for vigorous exercise or gymnastics I would screw the plywood to the 2x4's rather than nailing, and space at 1 foot intervals. Be sure NOT to put a solid edge around it, because you need free air flow under it.

Answered 6 years ago by LCD

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