Residential · Below grade
Basement floors move water. Coat them accordingly.
A below-grade slab sits on damp soil with no vapour barrier in older homes. Coat it like a garage and you get blisters within a year. The fix starts with a test, not a product.
The thing that decides everything
Vapour drive, measured before we quote.
Concrete below grade wicks moisture upward from the soil continuously. A coating is a vapour barrier. Put a barrier on a slab pushing more moisture than the primer tolerates and the pressure builds underneath until the film lifts off in discs.
So we measure rather than guess. Relative humidity probes set into the slab (ASTM F2170) and calcium chloride tests (ASTM F1869) give a number, and that number selects the primer.
If the reading is high, the answer changes
High vapour drive means a moisture-mitigating epoxy primer, not a standard one, or occasionally advice to fix drainage before spending money on a floor at all.
| Finding | What it means for the build |
|---|---|
| Low, stable RH | Standard penetrating primer. Normal epoxy or hybrid build, full finish choice available. |
| Elevated RH | Moisture-mitigating primer required before any decorative layer. Adds cost and a day. |
| Efflorescence on the surface | Salts are being carried up and deposited. The slab gets ground and neutralised, and the reading gets checked twice. |
| Damp patches after rain | This is drainage, not flooring. Grading, weeping tile or a sump issue gets addressed first or the floor will fail regardless of primer. |
| Existing tile adhesive or paint | Full mechanical removal. Cutback adhesive in particular has to come off, not be sealed over. |
Room by room
What people are actually coating down there.
Home gym
A hard, sealed surface under rubber tiles or a platform. Easy to clean, no dust from bare concrete, and it survives a dropped plate far better than paint.
Laundry and mechanical
Quartz broadcast for grip when the floor is wet, coved up the wall a few inches so a washer leak stays contained instead of running into the framing.
Workshop
Solid colour or light flake with a chemical-resistant topcoat. Spilled oil, solvent and adhesive wipe up rather than staining into the slab.
Storage and utility
The cheapest useful upgrade in a basement: a sealed floor stops concrete dust from settling on everything stored down there.
Finished rec room
Metallic or fine flake as the actual finished surface, which skips underlay and subfloor entirely and buys back headroom in a low basement.
Legal secondary suite
Worth flagging early: a suite has its own requirements around egress, ceiling height and fire separation. We coat the floor; we do not sign off on the suite.
Where we stop
Three basements we turn down.
- Active water intrusion. If water is coming in, no coating fixes it. It gets trapped underneath and the floor fails while the underlying problem gets worse out of sight.
- A slab that reads far above mitigation range. There is a point where the honest answer is a raised subfloor system rather than a coating.
- Coating over unremovable adhesive or a sound existing tile. If we cannot get to bare, profiled concrete, we cannot promise a bond, so we do not take the job.
Saying this in a quote costs us work occasionally. It costs less than a floor that peels in eighteen months.
Start with a moisture reading.
Tell us the age of the house, the room and what you have noticed on the slab. We will tell you what has to be checked before anything gets quoted.