Grinding is the heavier option, so it is fair to ask whether your floor really needs it. This article is about a repair or replace call: when you can keep the surface you have and repair it with a lighter prep, and when the old coating has to be ground off so the floor can be coated again from a sound base. It is general guidance, and the right answer for your slab depends on a site check.
What grinding replaces and what it repairs
Grinding is mechanical removal of the top of the slab, and it does three jobs at once: it strips old coatings, smooths uneven areas, and opens the concrete pores so a new coating can grip. Recommended Painters WA uses mechanical grinding and profiling to meet coating specifications for epoxy systems, concrete sealing and polishing, and industrial finishes. If your floor needs only one of those jobs, you may not need the full process. If it needs two or more, grinding is usually the sensible route.
When the old surface has to go
Replacing the coating, rather than repairing over it, is necessary when the surface itself will stop a new coating from bonding. The clearest cases are these:
- An old coating that is peeling, blistering or lifting, because a new coat over a failing one will fail the same way.
- A thick or unknown coating layer that has to come off before anything new goes on.
- A slab with noticeable unevenness, where high spots and dips will show through a thin coating.
- A smooth, dense or sealed surface that water will not soak into, which means a coating has nothing to key into.
- A floor going under an epoxy system or industrial coating that has a specified surface profile to meet.
A general rule of thumb: if you can see the problem in the surface, coating over it means you will see it again.
When you can keep the floor and prep lightly
A lighter prep can be enough on a sound, bare, reasonably porous floor that only needs cleaning. Think of a clean internal slab with no previous coating, no oil staining and no visible defects, going under a product that does not call for a mechanical profile. In that case degreasing and cleaning may be all the repair it needs, and grinding would be money spent for little gain.
The catch is that product requirements decide this, not your impression of the floor. Many epoxy and industrial systems specify a surface profile, and a floor that looks fine to the eye can still be too smooth or too contaminated to meet it. Ask whoever is quoting which profile the chosen coating needs and how they will confirm the floor meets it. If the answer is vague, treat that as a warning sign.
How do I know if my concrete floor needs grinding?
Check three things: whether there is an existing coating, whether the surface is level, and whether water soaks in or beads on top. Any coating that is lifting, any visible lumps or dips, or a slick surface where water beads all point towards grinding.
A simple home check is to sprinkle a little water on the slab. Concrete that darkens and absorbs it is generally more open. Concrete that holds the water in beads is sealed or dense and will probably need profiling. This is a rough guide only, not a substitute for a proper inspection. Recommended Painters WA begins each project with a clear site check to choose the right grinding and sanding method for the surface condition, which is the step that turns a guess into a decision.
The cost of skipping it
Skipping grinding when it was needed tends to cost more than doing it. Proper surface preparation reduces coating failure, peeling and early wear, and without it the usual outcome is blistering or peeling, then stripping the failed coating, then the preparation that should have been done at the start. The floor is out of use for each round.
Where the floor is a working one, such as a warehouse, workshop or factory, the stakes rise. Forklift traffic and machinery loads will find a weak bond quickly. For a residential garage the consequence is less dramatic but still familiar: a coating that lifts in patches under tyres, so the epoxy you paid for needs redoing.
Residential, commercial and industrial floors are judged differently
The same slab condition can lead to different decisions depending on how the floor will be used. A garage, patio or indoor concrete floor at home faces everyday wear, so the goal is a clean, level surface that holds epoxy, a sealer or a polished concrete finish. Commercial floors in offices, retail spaces and warehouses face constant traffic, so a marginal bond is less forgivable.
Industrial floors sit at the far end, where thick existing coatings, damaged slabs and specified profiles are common. If you manage a site rather than own a home, ask for the scope in writing, including how much of the existing coating will be removed and what surface result is being targeted. Our page on floor grinding and surface preparation in Perth sets out how these jobs are handled across residential, commercial and industrial spaces.
Questions to ask before you agree to grind, or not to
The quote should explain the reasoning, not just the price. Useful questions include:
- What is the current condition of the floor, and what did you see during the site check?
- Does the coating I have chosen require a specified profile?
- Is grinding needed across the whole floor or only in problem areas?
- How will dust be controlled, especially in an occupied building?
- What happens if grinding reveals a problem that was not visible before?
A provider who recommends grinding should be able to say why, and one who recommends against it should be able to say what they will do instead.
Frequently asked questions
Does a new concrete slab need grinding?
Not always. A new, clean slab may only need cleaning, but a smooth power floated finish can be too dense for some coatings, so check the coating’s requirements before deciding.
Can I just paint over an old floor coating?
Only if the existing coating is sound, firmly bonded and compatible with the new product. If it is peeling or blistering, painting over it carries the failure into the new coat.
Is grinding the same as sanding?
No, although both are used on concrete floors. Recommended Painters WA offers concrete grinding and floor sanding, and the site check is where the method is chosen to suit the surface condition. Grinding is the mechanical process that removes coatings, smooths uneven slabs and opens the pores for epoxy, paints and sealers.
Which kinds of floors does Recommended Painters WA grind?
It covers residential floors such as garages, patios and indoor concrete, along with commercial sites such as offices, retail spaces and warehouses, and industrial facilities such as factories and workshops across Perth.
Related pages
This article draws on the following pages.