Question: We live in Laurier, Man., about 270 kilometres northwest of Winnipeg. Our house is 12 years old. We are having trouble deciding how to finish our basement floor in the main area, which is about 700 square feet. Along the outside walls, some white crystals have formed. We aren’t sure what it is, but this will affect how we finish the floor. We had thought of getting the floor stained and sealed. We saw some Flexiplanks at the Winnipeg Home & Garden show and wondered if that would work, as they are easily installed and are not fixed or glued to the floor. I’m not sure how durable or practical that flooring would be.
If you could advise us of the best way to take care of this problem, it would be appreciated.
— Valerie Van Damme
Answer: The problem you are seeing on your basement floor is a common one and should not be a big issue in regards to new flooring. Your choice of flooring that is not secured is a good one for basements and should be quite practical for your purposes.
Choosing the right flooring for basements can pose several challenges. The most concerning issues apply to flooring that will be applied directly over concrete. Because concrete can be cooler than the surrounding area, condensation is a concern, even in an otherwise dry basement. This can occur after installing flooring, as the new surface material may allow warm air from the room to seep into the small space beneath the flooring. If this air cools past the dew point, because of the lower temperature of the concrete, condensation is likely. If the flooring has a means to let this moisture out, there should be little problem. But if the floor coverings restrict good air circulation, this moisture may remain long enough to cause concerns.
The least concerning of the issues surrounding this type of condensation is the formation of the "white crystals" you have identified. These are simply efflorescence — minerals leaching out from the concrete itself. This can occur if moisture is coming through the floor slab from below, but also from surface condensation. This may be what you are seeing, as you have described it being around the perimeter of the room. This is likely because of poor insulation and air sealing of the walls inside the foundation, or minor condensation if the walls are bare. This salty powder is generally harmless and can be removed by vacuuming or sweeping.
The only issue with the efflorescence is that it may make it more difficult for flooring adhesive to adhere to the concrete. For that reason, picking a floor covering that does not have to be glued down is a better choice. That way, you don’t have to worry about the adhesive letting go and your flooring lifting, buckling or becoming damaged if it pulls up off the slab. Also, if there is some leakage from a water heater, washer, heating or cooling condensate line, sump-pump pipe or floor drain, it is easier to pull up and repair the flooring than try to unglue permanently secured types.
The other benefit of vinyl plank flooring is the natural resistance to moisture. I am assuming the Flexiplank flooring you have seen is flexible, because it is made of solid vinyl. This relatively new style of floor covering does not have paper backing like many sheet vinyl products and should be solid all the way through. These plastic strips are completely resistant to moisture and normally interlock or click together to give the appearance of one solid component. Because of these properties, a small amount of leakage or condensation should cause little or no damage, which is all too common in basements. If damage does occur to this sturdy type of flooring, individual planks can be removed and replaced without the need to pay for an entirely new floor.
The only potential problem with this style of flooring is the chance of trapping moisture beneath the surface. Since it is plastic, it may prevent warm air leaking underneath, but will also prevent its escape, should any trapped air condense. It will be more likely to trap moisture than other, more breathable surfaces, which could create some efflorescence. Monitoring for the white powder around the edges or working its way up between the planks should allow for periodic cleaning or repairs.
Another method that can be used to help prevent efflorescence from being a nuisance is to install a subfloor, prior to the new flooring. Several manufacturers make a product that is a combination of tongue and groove OSB sheathing, normally in two-foot squares, with a dimpled plastic layer underneath. The idea is that the corrugated plastic layer will protect the wood-based OSB from damage due to condensation, from contact with the cold concrete. At the same time, the grooves or spaces between the dimples will allow a small amount of moisture to drain or evaporate due to increased airflow. The final benefit of this system is that the air space between the dimples, and the plastic layer itself, warms the surface of the subfloor by preventing direct contact with the cold concrete below. The vinyl plank flooring could be installed over top of this thin subfloor, making an excellent finished product, which should be warmer than if installed directly over the floor slab.
Simple removal of minor efflorescence on your basement floor with a vacuum or broom should allow installation of new flooring without much concern, as long as you choose the right material. Adding a subfloor system will also improve comfort, but removable vinyl plank flooring will be a good choice, regardless, for the various reasons presented.
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.