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pfisch 11-30-2008 07:42 PM

basement issues - tile, mastic, moisture
Good evening folks. Thanks in advance for listening.

My basement has some issues. Ultimately, my question will be "What should I do with my basement floor?", but it's a little more complicated than that.

Let me start with a brief summary of what's going on and then I'll hit you with some more specifics.

-My house is a 1940's colonial with a concrete block foundation.
-About two-thirds of the basement is carpeted (with a pad underneath), and the remainder is concrete.
-Underneath the carpet pad is 9x9 tile.
-Underneath the tile is a black mastic.
-The basement got wet one time in the two years that I've owned the house (crazy rain storm when the ground was frozen solid).
-In the summertime my dehumidifier runs pretty much nonstop.
-It looks like the previous owner may have had the basement finished at some point and then tore most of it out.

Now that you've got the picture......

At the beginning of the summer I forgot to turn on the dehumidifier and the high level of humidity caused a musty smell and I found mold growing on the underside of a shelf (a couple inches above the concrete floor). I got a mold test at HD and shipped the specimen off to a laboratory. The results showed mold, but none of the "bad mold" and the mold that did exist was not excessive.

I started removing the carpet and pad because I suspected they were retaining moisture and driving up the humidity.

That's when I found the tile. After a quick search on the web I found that it was likely asbestos containing tile and mastic. My best guess is that the tile is from the 60's or 70's, but cannot be sure. I contacted an abatement specialist and he told me to get both the tile and mastic tested. Based on everything I've read, I expected the results to come back positive for asbestos, but to my surprise the test was NEGATIVE.

The carpet must go, and much of the tile is chipped and in pretty bad shape. I don't think I can leave it there.

The asbestos test was negative, but I must admit I'm a little skeptical. Anyhow, I decided to start taking up some of the tile (wearing a respirator). Some of the tiles come up easy, but the vast majority of them take a LOT of effort and end up breaking into lots of tiny little pieces. The mastic is still there. I have no idea how I'm going to handle that.

I did about 1/10th of the basement...tough going so far. I think I need to step back and get a game plan and some solid advice before I get in any deeper.

In the end, I'd like to have a floor covering that could survive a freak storm. I haven't fully researched it yet, but I envision something rubber or plastic.

With that in are some of the questions kicking around in my mind:

Do you trust the results of the asbestos test?
Can I dispose of the tile as if it is clean?
Can the mastic be covered, or does it need to come up?
Can the concrete floor be sealed or does it need to breathe?

So, I've come back around to my original question....

What should I do with my basement floor?

Thanks again for listening.

butlersprints 11-30-2008 08:02 PM

I don't know for sure as to the specifics ,however you may want to wear a mask just in case, tear that stuff up, your already part way into it "git r done", :yes::laughing::thumbup:

Bud Cline 11-30-2008 09:18 PM


Do you trust the results of the asbestos test?
In my experience and with tile of that vintage I would suggest you have the tile and adhesive tested again if asbestos is a big concern for you. The years you mention absolutely did produce products containing asbestos.


Can I dispose of the tile as if it is clean?
As far as I know most all states provide for the means of a homeowner removing and disposing of asbestos -aden flooring products. Check with your local building authorities to see what the rules are in your location.


Can the mastic be covered, or does it need to come up?
The mastic used in those years to install that type of tile can in fact be covered in some cases. Most adhesive manufacturers are going to recommend that you do remove as much of the old adhesive as possible to where there is nothing more than a residue remaining.


Can the concrete floor be sealed or does it need to breathe?

Moisture in concrete floors especially below-grade concrete floors is always subject to moisture migration and should be addressed accordingly. You will hear of miracle products that will seal concrete floors but the truth is all concrete needs the ability to breath and to allow for natural evaporation of moisture from below.

Any topical sealer would likely fail over time and that would lead to even more issues.


What should I do with my basement floor?
That's a question only you can answer. Since the surface is already clad with adhesive it would probably be desirable to cover the floor with something. If moisture is an issue then carpet would be out in my opinion.

You mention rubber or plastic. Though some products in those categories do exist, unless they are 100% adhered to the substrate mold issues under the products could be a future issue.

My recommendation would be ceramic tile. Ceramic tile and some of its adhesives will be compatible with both the concrete subfloor, the existing adhesive residue you will have, and the ongoing moisture. Should you experience yet another water situation the tile could also easily survive such a disaster, even if it happened repeatedly.

Anyway, that's what I can offer with my thirty plus years of working with floor coverings and specializing in ceramic tile.:yes:

pfisch 12-01-2008 06:57 AM

Thanks for your input.

I don't have any experience with ceramic tile, but it sounds like a perfectly acceptable solution to me (and more importantly, my wife).

I think the floor is pretty flat, but will the mastic cause a problem if I need to use a floor leveling compound?

Bud Cline 12-01-2008 07:37 AM

It is very important to get the old mastic scraped away to nothing more than a residue. Then there are high strength thinset tile mortars available that can be used over previous cut-back adhesives.

Floor levelling compounds can be used but may require a primer. You'll need to check into that possibility based on what products are available in your area.:) For floor repairs I would recommend Mapei's Plani-Patch mixed with their additive.

Floor leveling (planing) products and Self Leveling Compound products should not be confused. There is a big difference between the two.:)

pfisch 12-01-2008 11:57 AM


What would you recommend for scraping away the existing mastic?



Bud Cline 12-01-2008 01:35 PM

We use a 3"-4" wallpaper type scraper with a long handle. The blades are razorblade type blades and do a good job. Turn the scraper over after every three or four passes to keep the blade half way fresh.:) It goes fairly quick.:) Not much fun but do-able.:)

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