How to remove leveling compound under carpet

Q. My wife and I bought a duplex in January. It may have been built as storage for a greenhouse/florist, which would explain why it is built with a shed roof (single slope roof I've heard referred to as a "flounder house"). The unit is two stories, about 500 square feet and with a full basement. Our upstairs tenant moved out in February and we had to have a contractor screw down the floor boards, as there were two layers of 3-inch planks on top of one another and set down parallel to one another.

Now the downstairs tenant has moved out and we need to replace the carpet, as they said it wasn't new when they moved in 17 years ago! When I took up a piece of carpet to see what was underneath, I found an old foam pad (Omalon system 350), and underneath that, something that looks like cement. Our contractor speculated that it could be cement mixed with gypsum. To me, it looks like maybe someone tried to smooth it out with plaster!

The reason I say that is it's white and when I knock on it, in places it has that hollow sound that plaster can have (which I don't think is a good sign!). Looking at the back of this floor from the basement, it looks like wood, so it seems that whatever this is was poured and added over wood.

Hopefully that gives you enough background information. Now my questions. First, the Omalon foam pad seems to have been glued down for about a foot around the edges of the room and at the seems. It wasn't until after I took up the pad with a plastic scraper that I thought about asbestos in the glue/mastic used to hold the foam down. I know you can't guarantee one way or another, but I just wondered if you might have an idea of what might have been used as an adhesive. Or perhaps you'd recommend I find someone like an environmental engineer to come and check it out?

My other questions are about the subfloor. As you can see from the attached pictures, it looks like cement and "plaster." I believe the trowel marks are from the glue for the carpet pad. The cement is pitted in places, and in there is some crumbling. The plan is to put down a pad and carpet, but I'm not sure how important it is for the surface to be smooth. If so, should I scrape the loose stuff and fill with something? The floor isn't very level and I'm sure the pad will mitigate small divots. Finally, in some places where the floor meets the wall, there is a gap. I think that should be filled in, but I'm not sure with what. Many thanks.

A. The whitish compound you see is a gypsum-based filler used to fill in the gaps between the wood boards you see from the basement and to level the surface before laying the pad and carpet. It needs to be scraped off, as it is not a sound material and it disintegrates easily, as you have found out. It does not contain asbestos from what my flooring expert friend told me.

The adhesive used to glue the Omalon pad should come up with the removal of the leveling material if, as I assume, it was applied over it. But if not, you can soften it with a hair dryer or heat gun and scrape it off with a broad-blade putty knife.

If the hair dryer does not take care of the adhesive removal, you may want to try pouring boiling water on a small area at a time, scrape the softened adhesive and move to the next spot - a couple of square feet at a time.

But, with a wood base underneath, you would have to be very careful not to use too much water in order not to damage the wood subfloor and to wipe as much of it as you can as soon as the adhesive is scraped off.

It is probably best to avoid this method unless the wood base is as sturdy as the one you found on the second floor.

Once the adhesive and the leveling compound have been successfully removed, have a cement-based product such as Ardex or equivalent applied to level the floor surface and fill in the gaps on the perimeter.

Q. Six years ago we purchased a "walk in" condo in New Haven, Connecticut. It is a rental for our son (yes he is paying rent!). The building is about 100 years old. It was converted into eight condos 25-plus years ago. This is the basement condo with an inside entrance and also has an entrance from the outside.

In the first few months of his living there, we noticed the brick is crumbling on the basement wall facing what would be the front yard. After putting in a dehumidifier, the crumbling stopped. Other brick walls in other parts of the condo, both painted and unpainted, were not crumbling.

We basically left it as is for the past six years. Now with his departure next summer, we are looking to sell the condo and need to do something about the wall. Is there a way to patch these walls where it would not crumble in the future? Is there also a way to give it the brick look that it had?

A. The damage your photos show is caused by moisture. It appears as if the grade outside this wall facing the front yard may be too flat or negative (slanting toward the building), which allows moisture to collect and seep against that wall.

The wall's waterproofing, if any was attempted, has not successfully kept the moisture out and the bricks have absorbed the moisture, which caused disintegration of the bricks, the mortar and the face coating that was applied over the bricks.

For a longer lasting repair, but not an absolute cure that would require expensive exterior repairs, correct any grade deficiencies in order for the soil to dry. This will require raising the grade to direct water away from the foundation and encouraging a healthy stand of grass to draw moisture out of the ground.

A mason should be able to scrape all loose stuff from the bricks, perform the necessary tuck-pointing and face repairs of the damaged bricks and apply a coating to match the existing. Hopefully, there will be no need to replace bricks that are too badly damaged.

Interesting follow up from an Illinois reader: "Your article in the Daily Herald's Sunday, Sept. 24, edition mentions problems with "black specs" in the water supply. That reader is on city water in Massachusetts, while I live about 30 miles west of Chicago and am on septic and a well. Nevertheless, the chemistry of water that comes out of the ground is often the same in many places. In my case, the well water contains both iron and sulfur compounds, but also a critter (an anaerobic bacteria) that mediates certain chemical reactions. Being anaerobic, it does not use oxygen but instead lives on sulfur. The result is hydrogen sulfide, the gas that smells like rotten eggs. But that then reacts with the iron to produce one of the forms of iron sulfide, i.e. black particles. Some are so fine they just turn the water gray, and others can build up to the size of a grain of sand.

"If left to collect in a drain pipe, this combination will, over years, set up like concrete and cannot be removed. Another characteristic is that, in a water pipe that often does not get heavy flow, the heavy iron sulfide will build up in the bottom of the pipe. Then, if an occasion arises when the water flow is greatly increased, some of the "black stuff" will be swept out with it.

"In your article, the questioner mentioned the water company using a chemical that appears to have been designed to reduce the adhesion of deposits along the pipes, and so could have dislodged iron sulfide deposits. If this is the case, the problem should reduce with time. In the meantime, however, the statistical variation in overall water use during the day can sweep out some of these deposits when net water flow hits a high.

"In my case, I now have a solution: I chlorinate my well with a couple of bottles of bleach twice a year to kill of the critters down there. That then prevents the chemical reactions which produce iron sulfide."

• Henri de Marne, a former remodeling contractor turned columnist and consultant, is the author of "About the House with Henri de Marne" (Upper Access Publishing). He continues to take questions from readers for this column and his website, www.henridemarne.com. Email questions to aboutthehouse@gmavt.net.