Concrete Grinding & Surface Prep, Collingwood

Nearly every coating failure we are called to look at is a preparation failure, not a product failure. The coating is fine. It simply never bonded to anything.

Grinding versus acid etching

A residential garage slab is usually power-trowelled, which closes and densifies the surface to a hard, almost polished skin. That skin is what a coating has to grip. Acid etching — the method in every hardware store kit — barely opens it, and it leaves salts behind that then have to be neutralised and rinsed, in a garage with no floor drain, in a region where the rinse water is going onto your driveway.

Diamond grinding removes the trowelled skin mechanically and leaves a measurable profile — the industry scale is CSP 1 through 9, and a thin polyaspartic or epoxy build wants CSP 2 to 3. We grind with dust collection at the tool, so the garage does not need re-cleaning afterwards and the silica ends up in a filter rather than in the air.

What a CSP 2 to 3 profile feels like under your hand

You can check this yourself, and it is worth doing before anybody opens a pail. A correctly ground slab has the tooth of fine sandpaper. A slab that has been acid-etched and called ready still feels like a finished floor. If you can run a palm across it and it feels smooth, nothing is going to hold on to it.

The moisture test, and why it happens before the quote

Concrete is not waterproof. A slab poured straight onto grade without an intact vapour barrier wicks groundwater up and pushes it out of the surface as vapour, continuously. Seal a coating over that and the vapour has nowhere to go, so it collects at the bond line and lifts the floor off in sheets. It can look perfect for a year first, which is the cruel part.

This is a live issue around here rather than a theoretical one, because vapour barriers under residential slabs were not standard practice for a long time. The floors it catches most often:

• Older cottages and garages on the sand at Wasaga Beach, where the water table is high and moves.
• Anything built close to the shoreline at Meaford or along the bay, for the same reason by a different route.
• Pre-1980 slabs generally, including the detached garages behind the older streets in Collingwood.
• Rural outbuildings of unknown age, where there is frequently nothing under the concrete at all.

We test with calcium chloride or an in-slab relative humidity probe, and we read it before quoting, because the result changes the job. A slab over the threshold needs a moisture-mitigating primer underneath the system. That is a real line item and a real cost — it is not an upsell, and you should see it on the quote rather than meet it on the day.

Control joints

The saw-cut lines in your slab are there so the concrete cracks where somebody chose rather than at random. They are still moving. Filling them flush and coating straight over is the standard shortcut, and the joint reappears as a split in the coating within a couple of seasons. They get filled with a flexible polyurea and honoured, not erased.