Why garage floors dust and how to stop it

That fine grey dust is your concrete breaking down. An epoxy system seals it for good — here is what the process involves.

Sweep a garage, come back a fortnight later and the grey film is back. That dust is not coming in from outside. It is the surface of the concrete itself breaking down, a few microns at a time, every time a tyre turns or a bike stand drags across it.

What is actually happening

A power-floated concrete slab has a thin, weak layer of fines and cement paste at the very top called laitance. It was never meant to be a wearing surface. Traffic abrades it, moisture rising through the slab pushes salts up through it, and the result is a floor that produces dust indefinitely and stains the moment oil or brake fluid touches it.

Why paint from a DIY shop peels

• It is applied over that weak laitance layer, so the paint is only as strong as the crumbly surface underneath it.
• There is no mechanical key — a quick sweep is not preparation.
• Moisture coming up through the slab has nowhere to go and lifts the film from below.
• Hot tyres soften single-pack floor paints and pull them off in patches when you drive out.

What we do instead

Every epoxy floor we lay starts with diamond grinding the slab back to sound concrete and vacuuming it clean. Cracks and pinholes are filled with a resin mortar, then a penetrating primer soaks in and binds the surface. On top of that goes a two-pack epoxy or polyurethane system, usually 400–600 microns, finished either smooth or with an anti-slip aggregate where cars are parked.

Nine times out of ten a failed floor is a preparation failure, not a product failure.

Cost and timescale

A single domestic garage is typically £900–£1,600, a double £1,500–£2,400, both usually done in a day with light foot traffic the next morning and cars back after about three days. Workshops and commercial units are priced per square metre and can include bay markings, walkways and coving.

Worth knowing before you book

If your garage has no damp-proof membrane under the slab, we test the moisture content first and use a damp-tolerant primer — skipping that step is exactly how floors blister a year later. We will also want the garage emptied, because a proper job needs the whole floor clear.

Choosing the right system for the room

• Domestic garage, cars and storage: a two-coat epoxy at around 400 microns, smooth or lightly textured.
• Home gym or hobby room: a polyurethane topcoat, which is more scratch and UV resistant and stays truer in colour.
• Workshop or commercial unit: a higher build system with anti-slip aggregate in traffic routes, plus bay and walkway markings.
• Wet or forklift areas: a screed-type system, several millimetres thick, rather than a coating.

Colours, flakes and markings

Mid grey remains the default because it hides tyre marks and dust better than anything else. Decorative flake systems — a broadcast of coloured chips under a clear coat — are popular for home gyms and hide small imperfections in the slab well. For commercial floors we can lay yellow walkway lines, hatched no-go areas and numbered bays as part of the same visit.

How to look after it

Sweep or vacuum the grit off, mop with warm water and a pH-neutral cleaner, and wipe up oil and brake fluid when you notice it rather than next month. Avoid dragging metal shelving legs across the finish and put a mat under bike stands. Looked after, a properly prepared domestic epoxy floor will still look good in ten years, and it can be re-coated rather than replaced when it finally dulls.