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QUESTION -- I hadn't been in my basement for a while, and when I went down there today, it was evident that there had been a fair amount of water towards one end.
The water is all dried up now, but there seems to be some sort of white crystalline growth on and between some of the tiles where the water had been, but not everywhere. What might this be, and what do I need to do to clean it up?
ANSWER -- Moisture intrusion into homes, particularly basements is the No. 1 complaint of homeowners, according to several surveys done over the years. It is not uncommon to have a small amount of seepage into basements, particularly on older homes this time of year. If the seepage is a small amount only seen in the spring, which drains toward the floor drain and disappears, it may of little consequence. Also, the white crystalline powder you are seeing is also of little concern and is harmless and I will offer some advice on cleaning as well as using this powder to gauge the level of concern.
When water comes in contact with concrete, particularly in areas with cracks or deterioration to the surface finish, it can produce the powdery substance you are seeing. This is properly known as efflorescence and is simply minerals and salts leeching out from the concrete. The water sitting on your concrete floor from the leaky basement will dissolve some of these minerals in the concrete so that they migrate to the surface with the water. Once the water evaporates, these minerals will precipitate out in a white crystalline form that remains on the surface of the floor. They do not normally contain any hazardous chemicals, but can be quite messy or slippery if present in sufficient quantity.
Cleaning up a small amount of this efflorescence may be done simply by sweeping or vacuuming of the whitish powder. If this does not complete the job, mopping with a damp mop or wet cloth will remove excess material, but quick drying of the excess water with rags or towels may be required to prevent its return. Opening basement windows to ventilate the area after mopping will also help dry the damp concrete and help prevent new deposits.
While the efflorescence itself is of little concern, the root cause, which is moisture intrusion, may point to significant problems or concerns. If the concrete basement walls and floors are unfinished and have minimal storage, there should be little to worry about. If the foundation walls are insulated, covered with wood framing or wall coverings then the water may lead to more serious issues if the leakage is ongoing. Mould can develop inside an insulated wall or on drywall or panelling that is in contact with water on the floor. Wet drywall is an excellent medium for mould growth, and may become mouldy in a very short time if it is allowed to remain wet. Also, cardboard boxes sitting on a damp concrete floor will not quickly dry after sitting in a puddle and will be covered with mould in short order. For this reason, drywall and wall coverings should be checked, especially near the bottom, for moisture stains and damage that may be a sign of further problems. This wall sheathing should be cut to remain at least two to three centimetres above the concrete floor slab.
Mould in damp basements is a growing concern with our homes becoming tighter with less air changes per day. Poorly ventilated basements will inhibit drying of wet building materials, so avoid excess storage in small areas and allow interior basement doors to remain open during the daytime for better air circulation. Also, running the furnace fan on continuous low speed will help move the air in the home and help dry any damp areas. As previously stated, open your basement windows on warm spring days, like those we are currently experiencing, to help remove excess moisture trapped over the long winter months.
The final item to address is the root cause of the foundation wall seepage. This may be caused by a number of factors, but there are several regular maintenance items that may require attention that will significantly reduce the potential for seepage. The first item to check is the downspouts on the exterior of the home. Nine times out of 10, when I see evidence of moisture in a basement it is inside the area where the downspout discharges at the exterior of the home. If extensions are not installed on the downspouts that divert water one to two metres from the foundation wall, leakage is highly likely, especially during the spring melt and heavy summer rainstorms. This excess water will find its way to any small crack or opening in the concrete and leak inside, if enough is present.
Grading of soil away from the foundation wall is the next item to check and the majority of homes require some remediation in this area. If there are depressions in the landscaping and soil adjacent to your home's foundation, water pooling is likely. Again, water pooling up against the foundation walls may find its way inside. Check regularly and top up the grading around the home with fresh soil and grass seed to prevent low areas that may allow pooling or rainwater.
Efflorescence in your basement may not be a problem, in itself, but may be a signal that further maintenance or repairs are necessary to maintain a dry basement and healthy indoor air quality.
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