So waterproof paint is a scam?

No, and be careful of anyone who says that either. It does a real job — reducing moisture transfer into interior finishes — and the Code asks for something in that role. The problem is that it is sold to people whose actual problem is a failed drain, where it cannot work, because the water is already through the wall by the time it gets there.

A company quoted me interior drainage rather than a coating. Is that different?

Very. An interior drainage system is a channel and a sump inside the footing, not a coating, and BC's Appeal Board has held it may be installed in addition to the exterior drainage the Code requires. That is a separate question and worth reading on its own.

My basement is dry and I want to finish it. What do I need?

That is exactly the situation the interior measure in 9.13.2.5 is written for — a separate interior finish going onto a concrete or masonry wall in contact with soil, or wood members placed against it. Ask the contractor which of the two things they are quoting, because the words get used interchangeably and they are not.

Why does every other page argue about products?

Because most of them are written by companies that sell one. The Code has no product to sell, which is why it starts with the condition of your wall instead.

Someone told me to paint or seal the inside of the basement wall. Does that actually stop the water?

Will sealing the inside of the wall fix it?

Direct answer · reviewed 2026-09-29

Almost every page you will find on this argues about products — whether this coating beats that one. The BC Building Code does not organise it that way at all, and once you see how it does, the question answers itself. Section 9.13 has two separate sets of rules, and what decides which one applies to your wall is not what you buy, it is the state of your drain: the dampproofing rules govern a wall whose perimeter drainage is doing its job, and the waterproofing rules govern a wall with standing water pushing against it. Both of those treatments live on the outside of the wall. What the Code asks for on the inside face is a different job with a different purpose — keeping moisture out of your studs and drywall — and nowhere does it treat an interior coating as the thing that keeps water out of the building.

Conditions and exceptions

This is not an argument that interior work is worthless. Protecting your finishes is a real job and the Code requires it in some cases. It is an argument that it is not the same job as keeping the water out.
If your basement is dry and you are finishing it, the interior measure is exactly what you want. If your basement is wet, it is not.
Nobody can tell you whether your drain is doing its job without a camera in it, and that includes us.

Drain problem assessment

Local evidence

Every figure below is quoted from the source shown or is our labelled estimate. Verified dates are the day we last checked the source; a figure whose check is overdue is withheld rather than shown.

What decides whether you need dampproofing or waterproofing: The state of the drain: the dampproofing rules apply where drainage is provided in accordance with Section 9.14 over and along the entire below-ground portion of the foundation wall, and the waterproofing rules apply where the assembly is subject to hydrostatic pressure; So the honest first question is not which coating to buy, it is whether the drain is doing its job · Hydrostatic pressure means standing water pushing against the wall, not damp; Province of British Columbia (BC Codes) · quoted · verified 2026-09-22
Where dampproofing goes: On the outside: exterior dampproofing shall be applied from finished ground level to the top of the exterior of the footing, on a surface that is clean, dry and free of ice, dust, oil, cracks and loose particles; Which is the same trench a perimeter drain replacement opens — the reason the two jobs are usually quoted together; Province of British Columbia (BC Codes) · quoted · verified 2026-09-22
What the Code asks for on the inside face: Not waterproofing, but protection of the finishes: the interior surface of foundation walls below ground level shall be protected by means that minimize the ingress of moisture into interior spaces where a separate interior finish is applied, or where wood members are placed against the wall; The job of the interior measure is to keep moisture out of your drywall and studs, not to keep water out of the building · Nothing in Section 9.13 treats an interior coating as the thing that excludes water; Province of British Columbia (BC Codes) · quoted · verified 2026-09-22
When waterproofing is actually required: Where hydrostatic pressure occurs, waterproofing is required for assemblies separating interior space from the ground, to prevent the ingress of water into building assemblies and interior spaces; Every material the Code lists for exterior waterproofing is a membrane or a sheet, not a paint; Province of British Columbia (BC Codes) · quoted · verified 2026-09-22

The Code splits this before it mentions a single product

Section 9.13 opens by saying which of its rules apply to what, and the split is the whole answer. The state of the drain: the dampproofing rules apply where drainage is provided in accordance with Section 9.14 over and along the entire below-ground portion of the foundation wall, and the waterproofing rules apply where the assembly is subject to hydrostatic pressure

Read that again slowly, because it inverts the usual conversation. The Code does not offer you dampproofing and waterproofing as two products with different price points. It looks at the wall, asks whether the drainage required by Section 9.14 is there and working, and on that basis decides which rules you are under. Your drain is the input, not the coating.

So a homeowner standing in a wet basement holding a tin of sealer is holding the answer to a question the Code never asked.

Both treatments go on the outside

On the outside: exterior dampproofing shall be applied from finished ground level to the top of the exterior of the footing, on a surface that is clean, dry and free of ice, dust, oil, cracks and loose particles

That is the same trench a perimeter drain replacement opens, which is why the two jobs are usually quoted together, and why doing the drain without the dampproofing is a missed opportunity that costs the same excavation twice.

And when the wall really is under hydrostatic pressure: Where hydrostatic pressure occurs, waterproofing is required for assemblies separating interior space from the ground, to prevent the ingress of water into building assemblies and interior spaces Every material the Code lists for that is a membrane or a sheet — EPDM, modified bituminous, PVC, hot-applied rubberised asphalt. None of them comes in a tin and none of them is applied from inside a finished basement.

What the Code actually asks for on the inside face

The interior is not ignored. It is just asked to do something else. Not waterproofing, but protection of the finishes: the interior surface of foundation walls below ground level shall be protected by means that minimize the ingress of moisture into interior spaces where a separate interior finish is applied, or where wood members are placed against the wall

Protecting the finishes. Keeping ground moisture out of the drywall and the studs you are about to put against a concrete wall. That is a real requirement and worth doing — on a wall that is already dry.

What it is not is a substitute for the drain. A coating on the inside face is downstream of the water: by the time it is working, the water has already crossed the wall.

The order that saves money

The reason this matters commercially is that the two answers cost about two orders of magnitude apart, and the cheap one is only cheap if it is the right one.

Find out where the water is arriving and when. A wet band along one wall after heavy rain is a drainage story; even damp everywhere with dry walls usually is not.
Get a camera down the perimeter drain before buying anything. Until that has happened, every recommendation you receive is a guess with a price attached.
If the drain has failed, deal with the drain. The dampproofing goes on while the trench is open, at a fraction of what it costs to reopen it later.
If the drain is sound and the basement is dry, then the interior measure is the right purchase — for protecting finishes, which is what it is for.

Questions homeowners ask

So waterproof paint is a scam?: No, and be careful of anyone who says that either. It does a real job — reducing moisture transfer into interior finishes — and the Code asks for something in that role. The problem is that it is sold to people whose actual problem is a failed drain, where it cannot work, because the water is already through the wall by the time it gets there.
A company quoted me interior drainage rather than a coating. Is that different?: Very. An interior drainage system is a channel and a sump inside the footing, not a coating, and BC's Appeal Board has held it may be installed in addition to the exterior drainage the Code requires. That is a separate question and worth reading on its own.
My basement is dry and I want to finish it. What do I need?: That is exactly the situation the interior measure in 9.13.2.5 is written for — a separate interior finish going onto a concrete or masonry wall in contact with soil, or wood members placed against it. Ask the contractor which of the two things they are quoting, because the words get used interchangeably and they are not.
Why does every other page argue about products?: Because most of them are written by companies that sell one. The Code has no product to sell, which is why it starts with the condition of your wall instead.

Your next step

The answer to the coating question depends entirely on whether the drain is doing its job.

Work out whether this is a drainage problem at all

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Sources

British Columbia Building Code 2018, Division B, Section 9.13 — Dampproofing, Waterproofing and Soil Gas Control — Province of British Columbia (BC Codes), accessed 2026-09-29
British Columbia Building Code 2018, Division B, Section 9.14 — Drainage — Province of British Columbia (BC Codes), accessed 2026-09-22

Code and municipal requirements are quoted from the sources above; price ranges are what named local companies publish, and the companies that publish them sell the work. Nothing here is a diagnosis of a particular house: only a camera in your own drain can tell you what is wrong with it. Report a correction.