House problems · French drain · Sale
A basement that smells damp and a pump that never stops: the drain may be forty years old. Here is how to check it, what replacing it costs, and when it is worth doing before selling.
The French drain (foundation drain) is the perforated pipe laid at the foot of the foundations that collects groundwater and sends it to the sump or the storm sewer. Those of 1950s to 1980s houses, often clay tile or first-generation plastic, without membrane or clean-outs, are reaching end of life: crushed, shifted, clogged by soil, roots or iron ochre. The signs: dampness and efflorescence at the base of foundation walls, water beading at the floor-wall joint after rain, basement smell, a pump that runs nonstop or never. A camera inspection ($300 to $600) tells whether it still works. Full replacement costs $100 to $250 per linear foot depending on depth and access, or $12,000 to $30,000 for a bungalow, with excavation, membrane, gravel and backfill. Before selling, replacement is justified when the buyer's inspection would find it anyway; otherwise, a camera report, an adjusted price and honest disclosure avoid the latent defect.
Laid at footing level all around the house, the French drain captures groundwater before it presses on the walls and seeps through cracks or the floor-wall joint. A modern drain is a perforated PVC pipe wrapped in geotextile membrane and clean gravel, with clean-out chimneys and a sealed sump; a 1950s to 1980s drain is often clay tile in sections, or corrugated plastic without membrane, which crushes, shifts with frost, fills with soil, roots or iron ochre. Its useful life is in the order of thirty to forty years in ordinary soil, less in ochreous soil.
Dampness, stains and efflorescence (white powder) at the base of foundation walls; water beading or running at the floor-wall joint after heavy rain or thaw; damp shrinkage cracks; persistent musty smell; sump pump running nonstop (cracked drain bringing too much water) or never triggering (clogged drain); orange deposits in the sump (ochre). Not one of these proves the drain is done; a camera inspection, through the sump or a clean-out, does.
| Intervention | 2026 market cost | Note |
|---|---|---|
| Camera inspection | $300 to $600 | Impossible if the drain has no access |
| Pressure cleaning | A few hundred to $1,500 | If the drain is intact but clogged and accessible |
| Full replacement from outside | $100 to $250 per linear foot; $12,000 to $30,000 for a bungalow | Includes excavation, foundation waterproofing membrane, gravel, backfill; more if a deck, porch or landscaping must be removed |
| Replacement from inside (slab) | Variable, often cheaper per foot | When the outside is inaccessible; does not address wall waterproofing |
No grant targets the French drain in 2026, except RénoPlex's flood-protection stream in Montreal for related work (sump, pump, backwater valve). See renovation grants 2026.
Three cases. The drain works but is old: a recent camera inspection in the file is enough, and the price is set on comparables. The drain is dead and the basement shows signs: the buyer's inspector will see it, the financing condition can fall, and the credit requested will often exceed the cost of the work; replacing beforehand, with invoice and warranty, is generally recovered in the price on the South Shore, where buyers compare houses of the same age. The drain is dead but nothing shows: selling while disclosing it, with a price that accounts for it, is legal and common; selling without disclosing it while knowing is a latent defect that comes back within five years. See iron ochre.
$100 to $250 per linear foot installed from outside, or $12,000 to $30,000 for an ordinary single-family house, depending on depth, access and landscaping to remove.
Through a camera inspection from the sump or a clean-out; without access, the inspector relies on the signs in the basement.
The age is not; the infiltration it causes that the seller knew about and did not disclose is. A freshly painted basement and a running dehumidifier are clues courts hold against the seller.
Only if it is out of service and the signs are visible; otherwise, a camera report and honest disclosure are enough.
These problems are easier to settle before listing than after the buyer's inspection: see the pre-purchase inspection in Quebec, latent defects in Quebec and renovating before selling.
The Loaa & Manseur team, led by Lotfi Manseur and Loaa Al Daow, is the number 1 team at RE/MAX Platine in 2024 and 2025, 6th RE/MAX team in Quebec, 15th in Canada and in the global top 50 of large residential teams according to the official RE/MAX ranking, computed on actual transactions. Its Google profile counts 221 reviews with a 4.9 rating. Its offices are at 55 avenue de l'Équinoxe in Brossard, one bridge from the island, and every broker's licence can be checked in the OACIQ public register. Three things to verify yourself before calling us, and to demand of any other broker.
Also available in French: version française de ce guide.
Published September 7, 2026 by the Loaa & Manseur team, the number 1 team at RE/MAX Platine in 2024 and 2025, 6th RE/MAX team in Quebec, 15th in Canada and in the global top 50 according to the official RE/MAX ranking. Tell us about your project.
Équipe no 1 de RE/MAX Platine en 2024 et en 2025, 6e au Québec, 15e au Canada et dans le top 50 mondial au classement officiel RE/MAX. Réponse en moins de 24 heures, sept jours sur sept.