Questions and answers
Plain answers to what Etobicoke homeowners ask about wet basements, grouped by topic.
Causes
Why did my basement start leaking after decades of being dry?
Usually because something outside changed slowly: the original weeping tile silted up, the ground settled so it now slopes toward the house, a downspout extension went missing, or a new driveway or patio sends water to the wall.
What is the white powder on my basement wall?
Efflorescence — mineral salts left behind when water passes through concrete or block and evaporates. It is harmless in itself, but it proves water is moving through that wall.
Is a damp, musty smell a waterproofing problem?
Not always. In summer, warm humid air condenses on cool basement walls and pipes. Tape a square of plastic to the wall for two days: moisture on the room side is condensation, moisture behind the plastic is coming through the wall.
Does waterproofing paint work?
It holds back dampness for a while on a wall with very light seepage. It does not stop water under pressure: the water lifts the paint off in blisters and sheets.
Methods and cost
What decides the price of a waterproofing job?
The length of wall treated, the depth to the footing, whether a machine can reach it, and what has to be removed and reinstated — decks, paving, planting or finished interior walls.
Is interior waterproofing a “band-aid”?
No. It is a permanent drainage system, and for some walls it is the only practical one. What it does not do is keep the wall itself dry, which matters for deteriorating block foundations.
Can I waterproof only one wall?
Yes. Both interior and exterior systems are installed along the walls that leak. The quote states exactly which lengths of wall are included.
Do I need a permit?
Permit requirements depend on the work. Ask the City of Toronto’s building division about plumbing work such as a backwater valve; the subsidy program separately requires that the installer holds a City of Toronto business licence.
Storms, thaw and the sewer
Why does my basement leak during a winter thaw?
The top layer of soil thaws and fills with meltwater while the ground below is still frozen, so the water cannot drain down. It runs sideways to the foundation instead. Ice in downspouts makes it worse by sending roof water straight down the wall.
What is the difference between a flood from rain and a sewer backup?
Rain and groundwater come through walls, cracks, the floor-wall joint or the slab, and the water is fairly clean. A sewer backup comes out of drains and fixtures, and the water is grey and smells. They need different repairs and are often treated differently by insurers.
Should I report basement flooding to the City?
Yes. The City of Toronto asks residents to report basement flooding by calling 311 or using 311 online.
Living with the work
Do I have to move out during the work?
No. Interior work is confined to the basement and exterior work to the yard. Water and power stay on except for short, announced interruptions.
Will mould go away once the basement is dry?
Mould stops growing when the moisture is gone, but what is already there has to be cleaned off or the affected drywall and insulation replaced. Large areas are a job for a mould remediation company.
When can I finish the basement after waterproofing?
New concrete over an interior drain needs a few weeks to dry before flooring goes on top. It is sensible to go through one wet season — a spring thaw or a run of heavy storms — before closing the walls in.
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