Question: I want to replace the tiles in a basement room on the north side of my house in south Winnipeg. The house was built in 1963 and the tiles were laid in the early 1980s using some kind of black glue. Some of the tiles are lifting or broken and there are white crystals forming under some. I vacuum up the crystals but they start to reform within a week. The clean-out for the sewer line is also in this room and a lot of crystals form in that area. I read this efflorescence is due to moisture under the floor. I had water coming into the basement on the south and east sides, probably because the weeping tiles were not draining well on those sides of the house. Last summer, I had the foundation repaired on the south and east sides from the outside. The foundation was patched, coated, received new weeping tiles and the space was filled with gravel. The weeping tiles on those two sides work really well now.
I’m wondering if the efflorescence in the room on the north side indicates I should have the same type of foundation work done on that side of the house? Both my neighbour and I have downspouts that drain near my northwest corner, with mine draining seven feet from the house. What type of flooring should I use or should I paint the floor? Should I go with a subfloor? I want a floor that is easy to mop. What kind of preparation should be done in advance?
Thanks, Jo-Anne Tabachek
Answer: Installation of flooring over top of a concrete basement floor normally poses several challenges, especially when there is a history of moisture, like in your home. Repairing the foundation damp-proofing and weeping tiles should ensure the efflorescence is minimized in the future, and give you more choice in the floor covering selection.
You are absolutely correct that the presence of efflorescence on the floor in your basement is an indication of moisture. It may indeed be coming from the soil beneath the concrete floor slab, but also may be due to periodic seepage through the foundation walls or the joint between the two. No matter what the exact location of the excessive moisture intrusion, proper exterior foundation repairs should eliminate the issue. The most important part of the repair may be replacement of older blocked or damaged weeping tiles with a new plastic drainage system. These corrugated pipes have small perforations that collect excessive ground water and channel it to the sewer or a sump. Collecting that water should also prevent seepage and excess moisture in the soil around the home and under the floor slab.
Since you have seen the positive results of the repairs in the other portion of your home, you should definitely have the rest of the foundation repaired if you plan to have a dry surface for your new flooring.
The choice of flooring and subfloor for the north portion of your basement floor should depend on the intended use of the area. Since you have specified you would like the flooring to be easily mopped, I assume you are using this area as a laundry or utility room.
If that is the case, a subfloor is not recommended, as it may be affected by frequent mopping, unless you use solid vinyl sheet flooring. The concern would be water seeping between the joints of any other type of flooring and wetting the surface of the subfloor, which is normally some type of wood-based material. Even if that type of subflooring is treated to make it more moisture resistant, it still may swell or become damaged if frequently wetted.
To allow installation of flooring directly over the concrete slab, you may have some significant preparation to do, ahead of time. Because a fair number of the older vinyl tiles are loose, damaged or missing they would all have to be removed. This may involve prying them off the concrete with a flat shovel or flooring scraper. Care should be taken to minimize damaging or scraping the surface of the old tiles as they may contain asbestos. If they can be removed with minimal effort, excessive efflorescence should then be remove by vacuum, sweeping, and damp mopping. While that job may require considerable elbow grease and will be messy, cleaning the adhesive beneath may be even more difficult. You may find much of the old, black adhesive may come off with the tiles and the white crystalline efflorescence, but there still could be quite a bit remaining after. You may have to remove this remaining layer to allow proper adhesion of new adhesive. Paint thinner or other solvents may be required for that job, which should only be done in a well-ventilated area.
If you are successful in removing most of the older adhesive, it should be sealed with an appropriate primer before painting, but that may be difficult to accomplish. Solid vinyl sheet flooring may be a better option for a surface that will stand up to constant mopping, without the need to completely remove the sticky black residue.
You could also use newer interlocking plank vinyl flooring but it may not stand up to regular wet mopping. Because that style of flooring has interlocking seams, prolonged wetting may cause the seams to lift or separate if water leaks through from the surface.
Professional foundation repairs on the exterior of your home will ensure continued problems with efflorescence and basement moisture are eliminated or minimized before replacing your flooring. Using solid vinyl flooring materials without a wooden subfloor may be your best choice, not because of basement moisture but to allow frequent wet mopping. Other floor coverings may not withstand the continual wetting from the mop and may create a similar situation to what you have now.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the past president of the Canadian Association of Home & Property Inspectors — Manitoba (cahpi.mb.ca). Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at trainedeye.ca.
trainedeye@iname.com
