Many Melbourne homes sit on a concrete slab hidden under carpet, tiles, timber or vinyl. During a renovation, a common question follows: can that concrete become the finished floor?
In many cases, yes. Polished concrete floors on existing slab surfaces are achievable when the concrete is sound and free of problems that grinding cannot fix. Much depends on the slab itself. Most existing slabs were poured to be covered, not displayed, so their condition decides what kind of finish they can realistically deliver.
The mechanical process of polishing includes the treatment of the slab using a chemical densifier that will toughen up the surface of the slab and then grinding with increasingly finer diamond grinders. A process known as the grind and seal, in which the slab is ground and then sealed, is another type of finish, as are decorative overlays.
A slab poured for polishing is finished with the final look in mind. An older slab laid under floor coverings was not, so the result is harder to predict. Its age, strength and the way it was originally poured all affect how residential polished concrete floors will look once the surface is ground.
Stone exposure is a good example. The aggregate, meaning the stones mixed through the concrete, may be spread unevenly, and you won’t see exactly how it looks until grinding starts. Some homeowners enjoy that variation, while others expect the uniform look of a new build.
Before recommending polished concrete floors on existing slab areas, an experienced installer will inspect the concrete in person. Cracking is a key concern, particularly whether cracks look stable or suggest ongoing movement. Many Melbourne suburbs are built on reactive clay soils that can cause slabs to shift, so this deserves a careful look.
They will also check for residue from old floor coverings. Tile adhesive, carpet glue, paint and old sealers generally need to be ground off, and oil or chemical contamination can cause discolouration that shows through the finish. Tack strip holes, chips, uneven areas and patches from past plumbing or electrical work will be noted too.
Cracks and holes can be filled, but repairs rarely disappear. Filler usually differs in colour and texture from the surrounding concrete, so it stays visible after polishing. In case you desire a uniform look, bring this up before starting any process.
As soon as the slab is ready, a course grinding is done to roughen the surface, and a densifier is put in, followed by fine polishing till the desired gloss level is achieved, from matte to ultra-gloss finish.
Some slabs are too damaged, contaminated or inconsistent to polish well. A grind and seal can bring out the existing character of an older slab, while a decorative coating over the top can give a more uniform finish. A good installer should tell you plainly if polished concrete floors on existing slab areas are unlikely to meet your expectations.
In a renovation, timing matters. Residential polished concrete floors are generally best done after demolition and heavy trades, but before cabinetry and skirting boards go in, so plan early with your builder.
For a family home with kids and/or animals, the polished concrete floor provides a flooring option that is both easy to clean and durable. Concrete flooring could be cold when standing on it in Melbourne’s winter season, making rugs or even a floor warmer advisable.
Peeling up just a tiny part of the carpeting will provide you with an initial look at the slab, but the best information is through an on-site visit. At Urban Concrete Floors, we can conduct a slab assessment for you, advise you about suitable finishes, and even display samples at our Thomastown showroom.
Often, yes. Tile adhesive can usually be ground off, but removing tiles may leave marks, chips or patches. The slab should be assessed after the tiles come up to confirm what finish is realistic.
Often yes, since the cracks can be filled, but the filler would seldom match the existing concrete perfectly. While many people will view this as part of the concrete’s charm, others will opt for a grind-and-seal finish or other decorative finishing.
Yes, especially in areas like living rooms and kitchens. Think about how comfortable it might feel to walk on concrete flooring in bare feet, and discuss slip-resistance issues in wet areas such as bathrooms and laundry rooms.
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