What it is
A perimeter drain, also called drain tile or weeping tile, is a pipe laid beside the footings in a bed of drain rock. It collects water from the soil around the foundation and carries it to the storm sewer, a sump or a rock pit. Older homes may have clay tile sections laid end to end with small gaps, or early fibre pipe that can soften and deform over the decades. Newer systems use perforated plastic pipe, often wrapped in filter fabric, with cleanouts at grade.
Over time, fine soil washes into the pipe, roots grow into joints and perforations, and old tile can shift or break. When the drain can’t carry water away, water builds up against the foundation walls.
Signs to watch for
- Damp walls, water at the base of basement walls, or white mineral deposits called efflorescence
- A musty smell in the basement or crawlspace
- Downspouts that empty against the foundation, or ground that slopes toward the house
- Soggy patches or standing water next to the walls after rain
Why it matters
A failing drain usually shows itself slowly, as dampness and staining, and then as water on the floor in a heavy rain. Replacing a perimeter drain means excavating around the house, so it’s a major project and one to know about before you remove subjects. A camera scan shows whether the drain is open, partly blocked or broken, and flushing can clear a drain that is silted up but intact.
What to do
- Older homes, or any home with signs of moisture: before subject removal, have a drainage contractor scan the drain with a camera and flush it.
- Newer homes: a scan and flush in the first few months gives you a baseline.
- Every year: keep gutters and downspouts clear and the ground sloping away from the walls.
What our inspection covers
Outside, we look at grading, gutters, downspouts and any cleanouts. Inside, we check foundation walls, floors and the crawlspace for staining, efflorescence and dampness, using a moisture meter and thermal imaging on finished walls. We can’t see the buried drain or run a camera through it, and a dry spell can hide a problem that only shows in heavy rain.
Inspecting an older house? Book an inspection, and read how we approach character and heritage homes.
Reviewed October 26, 2026 by Nick Hawley, Watch House Inspections. General information, not advice about a particular home.