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Discussion Forum

Mold in Carpet on Slab Foundation

Tyre | Posted in General Discussion on July 21, 2005 12:07pm

Hi Folks,

I’ve been searching through previous posts, and I’m getting some good ideas on how to approach my problem, but if anyone has additional insight, I’d be grateful.

Our master bedroom is carpeted, and we’re planning to replace the carpet soon. In one particular corner (along an outside wall) next to the closet, the carpet stinks, and in the past we’ve seen mold on the walls. The original house is 50+ years old, and the addition, which includes the master bedroom, is 30+ years old. The original home has a crawlspace, but the addition sits on a slab. A few months ago we replaced the old window with a new double-paned window, and that seems to have helped – we’re not seeing much, if any, mold lately. However, this carpet smell is bad, and I want to fix any moisture issue(s) before installing the new carpet. From what I’ve read here, my plan is:

1. laying down some plastic under the carpet for a day or 2 to determine if any moisture is seeping up from the foundation;
2. checking the relative humidity might help;
3. rip out the carpet;
4. clean any mold and examine the state of the subfloor;
5. dry out the floor with dehumidifier

I don’t know if there is a vapor barrier between the slab and the subfloor. Should I tear out the subfloor and put a VB in place, possibly on top of a sealant? Some posters have also suggested plastic-backed plywood.

I’m in Southern California, and the winter was quite a wet one for us. Plus, the house has some design issues. There are no rain gutters on any of the addition – I plan to put some in. Along the master bedroom exterior wall, I don’t think that the ground is very well graded, so water may pool along the slab (planning to address this as well).

Any ideas? Sorry for the lengthy post. Thanks.

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Replies

  1. DANL | Jul 21, 2005 12:39am | #1

    As I was reading your post I was thinking of the interlocking squares of plywood with the plastic waffles on the bottom (for the life of me, cannot remember what they're called, but I've seen them at places like Home Depot). That would at least keep the carpet up out of any wetness. Nonetheless, you should find the source of the dampness and eliminate it. New window may help--what about roof; is it draining away from house (is ground graded to slope away)?

    1. Tyre | Jul 21, 2005 01:16am | #3

      Hi Danno,You helped me out with my post on Cupped Hardwood Flooring several weeks ago. I almost mentioned that post, since this is all related, but decided that this current post was already too long.Thanks for the plywood/plastic tip, I'll look for it. Does that mean you suggest replacing the subfloor? The roof exceeds the wall by about 18" (maybe 24"), but because I'm suspicious of the ground outside the exterior wall, I'm going to hang gutters (of course, some of the wood is rotted, but that's another post...) The ground is covered with gravel, and I suspect the grade is not away from the wall. In the future we may pave it, but I'm planning to install some drainage next to the wall. A friend of mine recommended a product called Akwadrain, which he said worked nicely during some of the recent hurricane-related weather in his area.

      1. DANL | Jul 21, 2005 03:44am | #5

        It sort of worries me when people actually follow any advice I give, but if it worked, all the better! Since the carpet is toast anyway, I'd pull up the nast corner for starters and see how bad the subfloor is. If it is damp, rotten, or smells, I'd investigate further and consider taking it out too.

        Definately get the water coming off the roof away from the house and installing any sort of drainage system to keep water from the foundation would be good. A while back a guy wrote about a shallow trench he lined with an impermeable membrane and sloped it away; that might work for you. In any case, grading away from the foundation would help too. No sense in replacing the carpet and/or the subfloor if the cause of the problem isn't taken care of. The moldy smell is bad enough, but the dampness (and the mold) isn't healthy for you or the house.

        What you proposed in the numbered bullets in your first post makes sense. Your idea of taping plastic sheeting down to the concrete slab to see if water is comeing through from below or condensing from above is a good start. A floor on sleepers or that sytem I mentioned earlier (usually used in basements) might work. In any case, I would get the water away from the house, then look into the repairs.

        1. Tyre | Jul 21, 2005 08:44am | #7

          Thanks again for the advice, Danno. I've only briefly pulled up the carpet, but I recall that there was some type of subfloor. I plan to check again by the end of the week. And I agree completely - no sense in new carpet if the underlying (sorry, bad pun) issue isn't addressed. I live near the beach, so while we don't get much rain (except sometimes during the winter), we do get a lot of marine layer weather. Unfortunately, this side of the house doesn't really dry out well, so fixing the drainage problems are crucial.

      2. User avater
        BillHartmann | Jul 21, 2005 03:50am | #6

        Just what is the construction in that area.You indicated that it is a slab. And usually carpet (and pad) is laid right over the slab, no sub-floor.I wonder if that had been a garage and it was 6" or so below the rest of the house and sleepers where added?

        1. Tyre | Jul 21, 2005 08:56am | #8

          Bill,Actually, our garage sits in the front of the lot. The home was extended back into the lot about 30 years ago, and the owners decided to pour a slab foundation that butts up against the original crawlspace. At least, this is what I can assess from getting under the house. When I pulled up the carpet, I recall that there was a subfloor, but I didn't really examine it closely. I hope to pull up the carpet this weekend, if not sooner, and get a better picture of what's going on (now that I've got a better understanding of the topic, thanks to this forum). Unfortunately, I forgot to put down the plastic to test for moisture tonight, but maybe tomorrow. Anyway, I'm confident that this room was always the master bedroom, never a garage. That doesn't mean that it was built correctly, though.Thanks

          1. mbdyer | Jul 21, 2005 11:58pm | #9

            Solving the water infiltration problem is definitely key.  You mentioned that that side of the house doesn't dry out very well.   This may indicate a problem with the siding there.  One water gets in and then two it doesn't evaporate quickly.  That wall may need a residing soon, with extra water resisitant barrier and the siding stood off from the wall so that it can breath (as in cedar shingles), even if its T-111.  If the walls are stuccoed, then you may get away with a super thorough caulking and crack filling.  Check the roofing above, make sure the water is shed into the gutters without running behind and then behind the fasia and siding.   Depending on how long you've been in the house, if the dampness is from a scent marking cat, it must have been one helluva cat!

          2. Tyre | Jul 22, 2005 12:43am | #10

            My suspicion is that this side of the house doesn't dry out well. Actually, I should qualify that: I believe that this portion of this side of the house doesn't dry out well. Toward the front of the house on this side, the house gets much more sun exposure, and the ground is paved and designed for better drainage.The exterior walls are stucco. I'm not following you on how to caulk the walls, can you clarify? Filling the cracks seems straightforward. I think that cat was in our previous home, but I may be mixed up - need to check with my wife for the official record.Thanks again for the help.

          3. mbdyer | Jul 23, 2005 11:32pm | #11

            Go over the wall with a close eye.  Look at the top edge of the stucco, corners, windows, anything protuding.  Caulk all the seams with the best exterior caulk you can get except along the ground, let that alone to let any drips out.  If there are any cracks you could caulk them as well but a stucco pro would know a better solution, probably some sort of mortar mix; scratch the crack open, fill in new stucco, etc.  Not really my field.  Is there plumbing in the wall?  A leaky pipe joint perhaps?

          4. Tyre | Jul 24, 2005 07:13am | #14

            Awesome, many thanks for the clarification. I don't believe that there is any plumbing in the wall, but I should check again (no, don't make me go into the attic). I just noticed some mold again on an endtable in the bedroom (right next to the main problem area), so the problem hasn't gone away of its own accord. I've yet to put down the plastic under the carpet, here's hoping that I can do it tomorrow.Thanks again.

    2. immrfxit | Jul 24, 2005 03:08pm | #18

      The 2' x 2' square panels are called DRIcore, and are available at the Home Depot for about $5.50 each.

  2. mbdyer | Jul 21, 2005 01:04am | #2

    I know I'll catch hell for this but...carpet is an evil funk sponge that soaks up all the goop living things ooze and stews it and brews until stains your socks when you walk across the squishing carpet.   Rip it out, floor the room with wood, tile, bamboo, floating laminate, asphalt whatever.  Throw down a throw carpet(sic) or area rug that you can easily remove to clean or toss.  You stated that the dampness in the corner has abated but is still pungeunt; did you run out of whiskey or has a pet passed away?

    1. Tyre | Jul 21, 2005 01:24am | #4

      You may catch hell for the post, but not from me. I would be happy to put down some hard flooring, but my wife wants carpet in the bedroom. However, depending upon what I find when I rip up the carpet, I may try to convince her otherwise. Plus, not that you would know, a few weeks ago I posted on cupped hardwood flooring, which I would venture is related to the moisture problem that I'm having with the carpet. No pets, and I don't drink whiskey (usually), so I'm sticking with my mold story. Although, now that you mention it, I'm trying to recall if the previous owner had a cat...Thanks

    2. User avater
      rjw | Jul 24, 2005 12:16am | #12

      >>I know I'll catch hell for this but...carpet is an evil funk sponge that soaks up all the goop living things ooze and stews it and brews until stains your socks when you walk across the squishing carpet. I'm with you.I'm convinvced I read advice at the EPA's mold pages a couple of years ago recommending against carpet in basements for that reason, but when I went back to confirm and log it, I couldn't find it.SO, watch your 6 for the American Association of Sellers of Carpet (ASSCARP) <G,D&R>

      View Image

      Sojourners: Christians for Justice and Peace

  3. billyg | Jul 24, 2005 05:20am | #13

    You're on the right track with your fixes to keep the water away from the slab.  If your wife wants carpet on a cement slab I would put some 1 inch XPS or EPS foam panels on the floor and screw two layers of 1/2 inch plywood over the foam.  The first layer of plywood is screwed through the foam to the slab using Tapcons.  The second layer of plywood is laid perpendicular to the first layer and is screwed just to the plywood, not to the slab.  Check out the basement article by Andy Engel in a recent FHB (or search Breaktime for follow-up comments).  It will cure a lot of your stinky-carpet-on-a-slab problems and make the room more comfortable.

    Be sure to implement your other fixes as well.

    Billy

    1. Tyre | Jul 24, 2005 07:45am | #15

      Thanks for the detailed information and the vote of confidence, Billy. Very helpful. I plan to search for the FHB article shortly, and then I'm off to the store tomorrow morning.

      1. msm | Jul 24, 2005 08:21am | #16

        tell your wife that it's not just a guy thing to want to put down flooring other than carpet. i'm trying to convince my husband to get rid of even the rugs in most rooms. all the advice sounds great, but with the history of mildew in this area, i would not want carpeting down again. maybe , as mentioned, mats or area rugs, but never again carpet.

        1. Tyre | Jul 24, 2005 08:42am | #17

          I'll go wake her up now to tell her ;-) Actually, she only wants carpet in the master bedroom - unfortunately, it's the worst room in the house with regard to moisture, etc. And to be fair, until my buddy steered me to this forum, I knew less-than-zero about flooring/carpet. Ignorance is bliss...Thanks

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