Perimeter drains are the perforated pipes buried against the outside of your foundation footing, circling the house below basement floor level. They collect groundwater and carry it away before it presses against the wall. BC's Building Code requires drainage at the bottom of every exterior foundation wall unless it can be shown to be unnecessary. When perimeter drains fail, the evidence shows above ground long before water reaches the basement.
What perimeter drains are supposed to do, in the Code's own numbers
A working perimeter drain is an assembly, not a pipe. Sentence 9.14.3.2.(1) of the BC Building Code sets the pipe itself at not less than 100 mm in diameter, and Sentence 9.14.3.3.(1) requires it to sit on undisturbed or well compacted soil with the top of the pipe below the bottom of the floor slab or the crawl space ground cover (BC Building Code 2018, Section 9.14. Drainage).
The part that decides whether it keeps working is what surrounds it. Sentence 9.14.3.3.(4) requires the top and sides of the pipe to be covered with not less than 150 mm of crushed stone or other coarse clean granular material containing not more than 10% of material that will pass a 4 mm sieve (Section 9.14. Drainage). That 10% limit is the whole design in one number. Fines are what plug a drain, so the Code caps them.
Water gets in through gaps the Code puts there on purpose. Sentence 9.14.3.3.(2) requires drain tile with butt joints to be laid with 6 mm to 10 mm open joints (Section 9.14. Drainage). Those openings are the inlet, and they are also the way silt and fine roots get in once the clean stone around them has been contaminated by soil. A perimeter drain rarely wears out. It fills up.
The seven signs, ordered by what you can check without a contractor
The useful ordering is not severity, it is accessibility. The first four you can check yourself on a wet afternoon. The last three need a look inside the house or inside the pipe.
| What you see | How to check it | What it points at |
|---|---|---|
| Water standing in a window well | Look during or just after heavy rain. Water should not sit. | The strongest single sign. The Code requires every window well to be drained to footing level. |
| Pooling against the foundation | Walk the full perimeter in the rain, not after it dries. | Surface water is not being shed, and whatever reaches the footing has nowhere to go. |
| Ground that stays soggy for days | Press a screwdriver into the lawn beside the wall two days after rain. | Saturated soil against the wall. Dense marine clay under much of Greater Victoria holds it there. |
| Nothing running at the outlet | Find the discharge point and watch it during a downpour. | A loop that collects water but never delivers it is blocked somewhere between the two. |
| Efflorescence or dark tide lines inside | Check the bottom 600 mm of basement or crawl space walls. | Water has been moving through the foundation long enough to leave mineral residue behind. |
| A crack that weeps only in wet weather | Mark a dry crack with tape, then look again mid storm. | Hydrostatic pressure building against the wall, which is the pressure the drain exists to relieve. |
| A drain scope that finds silt, roots or a break | A camera run through the loop, usually at a cleanout. | Direct evidence rather than inference. This is what a buyer or an insurer will ask for. |
Why the window well is the sign worth trusting most
Because it is the one the Code answers directly. Sentence 9.14.6.3.(1) requires that every window well be drained to the footing level or other suitable location, and Sentence 9.14.6.1.(1) requires the site to be graded so water will not accumulate at or near the building (Section 9.14. Drainage).
So a window well holding water is not ambiguous the way a musty smell is. It is a built drainage path that has stopped draining, a few feet from the foundation, at the exact depth the perimeter loop runs. Most of the other six signs have a competing explanation. This one has very few.
What every other list of signs leaves out
The common assumption is that a failing perimeter drain is an old pipe at the end of its life. A large share of failures in older Greater Victoria houses are something else entirely: surface water being fed into a pipe that was never permitted to carry it.
The BC Building Code Appeal Board ruled on exactly this. In decision #1226, a driveway's two area drains had been connected into the house's perimeter drainage system. The Board found that foundation perimeter drains are perforated subsoil drainage pipes which cannot form part of a storm drainage system, and that the area drains had to be connected to the storm sewer in approved solid pipe instead (BCAB #1226, Area Drains, December 18, 1990).
The Code treats roof water the same way. Article 9.26.18.2. requires that where downspouts are provided and are not connected to a sewer, extensions carry rainwater away from the building (BC Building Code 2018, Section 9.26). A downspout discharging into the subsoil loop is sending a roof's worth of silted surface water through 6 mm openings designed for slow groundwater seepage.
This matters for what you do next. If the drains are silted because a downspout or a driveway drain has been feeding them, replacing the pipe without separating those inputs buys a new drain that fails the same way.
What to rule out before concluding the drains have failed
Water in a basement or crawl space is an indicator of a missing, clogged or broken drain pipe, and it also has other causes. The US Department of Energy's builder guidance is blunt about the order of operations: replacement is labour intensive and involves excavating the perimeter to the footing, so before committing to it, confirm that gutters and downspouts are installed and working, that there are no plumbing leaks below, that there are no cracks or gaps giving water a path through the wall, that the final grade slopes away from the foundation, and that patios, walkways and driveways slope away from the house (Footing Drain Pipe, Building America Solution Center).
The same guidance sets the target for where the water is supposed to end up: collected drainage should leave in unperforated pipe and discharge above grade at least 10 feet from the foundation, or to a drywell, an approved storm sewer, or a sump (Footing Drain Pipe). BC's own rule is stricter about drywells, which Sentence 9.14.5.3.(2) places not less than 5 m from the building foundation (Section 9.14. Drainage). An outlet that dumps against the wall recirculates the problem no matter how good the pipe is.
What confirming it actually takes
Two or more signs together is the threshold where guessing stops being useful. Confirmation means a camera run through the loop, which shows whether the pipe is silted, root filled, crushed, disconnected or simply absent. A Metro Vancouver plumbing firm publishes $250 to $500 for that camera inspection, often credited toward the work (HYDROPRO Plumbing, Perimeter Drain Cost by Scope, 2026). That is the number that decides whether the rest of the conversation is a section repair or the whole perimeter.
It is also worth knowing that an absent drain is not automatically a defect. Sentence 9.14.2.1.(1) requires foundation wall drainage unless it can be shown to be unnecessary (Section 9.14. Drainage), and a house on free draining granular ground can legitimately have none. A scope that finds no pipe is the start of a question, not the end of one.
So what do you do now?
- One sign, and it is surface water. Fix the grading, the downspout extensions and the driveway drainage first. That is the cheapest test there is, and the Appeal Board decision above explains why those inputs do not belong in the loop.
- Standing water in a window well, or two or more signs together. Get the loop scoped before anyone quotes you. If it comes back silted or broken, you are looking at perimeter drain replacement, in whole or in part.
- Wet ground and a soggy yard, but a sound foundation. The problem may be surface and shallow groundwater rather than the foundation loop, which is what French drain installation addresses. The two are different pipes doing different jobs, set out in French drain vs perimeter drain.
- Damp, musty air and cupping floors above. The moisture is coming from below and the fix usually starts with crawl space drainage rather than the perimeter.
If you want a second read on what you are seeing, send us the details and a few photos and we will tell you which of the four you are probably in.
Estimates vary by property. Book a site assessment for a scope and price specific to your home. Foundation drainage problems require an on-site inspection to diagnose.
Sources
- BC Building Code 2018, Division B, Section 9.14. Drainage (Province of British Columbia, 2018)
- BC Building Code 2018, Division B, Section 9.26 (Province of British Columbia, 2018)
- BCAB #1226, Area Drains (BC Building Code Appeal Board, December 18, 1990)
- Footing Drain Pipe (Building America Solution Center, US Department of Energy)
- Perimeter Drain Cost by Scope (HYDROPRO Plumbing, 2026)