Walk into a hardware store and the sealer aisle offers you a dozen tins that all claim to protect concrete. They are not interchangeable. The wrong choice on a driveway means a cloudy, peeling surface in two summers, and stripping a failed topical sealer costs more than sealing the slab properly would have in the first place.
Here is what each type actually does, and which one belongs on which surface.
The one distinction that matters
Every concrete sealer is either a film-forming sealer that sits on top of the slab, or a penetrating sealer that soaks in and reacts inside the pores. Nearly every sealing failure we are called to look at comes from putting a film where a penetrating sealer belonged.
A film gives you gloss, colour enhancement and a surface that is easy to sweep. It also has a service life, because it is a coating, and coatings wear, yellow and eventually peel. When it fails it fails visibly and it has to be stripped.
A penetrating sealer changes nothing about how the slab looks. It cannot peel, because there is no film to detach. It also will not make your exposed aggregate pop, which is usually what people were hoping for.
We have written separately on how long each type really lasts on Sydney stone and concrete. This piece is about choosing between them.
Acrylic
The most common and the cheapest. A thin film, available solvent-based or water-based, usually two to three years on a driveway before it needs recoating.
Solvent-based acrylics give a stronger wet-look and deeper colour enhancement. Water-based are lower odour, less glossy, and much less likely to go white if there is any moisture in the slab.
Good for decorative concrete where appearance is the point — exposed aggregate, stencilled and stamped concrete, coloured oxide slabs.
The weaknesses are real. Acrylic is soft, so tyres mark it, and a car parked on a hot acrylic-sealed driveway can leave the tyre print permanently. It is not resistant to much in the way of chemicals. And in full western sun, which describes a lot of Sydney driveways, it degrades faster than the tin suggests.
Penetrating sealers — silane, siloxane, silicate
These soak into the concrete and react with it. There is no coating, no gloss, no change in appearance, and nothing to peel.
Silanes and siloxanes line the pores and repel water. Water beads and runs off, and the slab stops absorbing salt and moisture. Typical life is five to ten years, considerably longer than any film.
Silicates — lithium, sodium or potassium — react with free lime in the concrete to form additional binder, hardening and densifying the surface rather than waterproofing it. Used on garage and warehouse floors to cut dusting.
For a plain concrete driveway in a coastal Sydney suburb, a silane-siloxane is usually the right answer. It defends against the actual threat, which is salt and water getting into the slab, and it does not have a cosmetic failure mode. Clients who want their driveway to look wet are disappointed by it, and that is the trade.
Polyurethane
A much tougher film than acrylic. Strong abrasion and chemical resistance, high gloss if you want it, five to ten years in service.
It is also unforgiving. Polyurethane does not tolerate moisture in the slab during application, it usually needs a primer, and recoating means proper surface preparation rather than a quick wash and another coat. Aliphatic polyurethane holds its colour in sunlight; aromatic will yellow outdoors, and that distinction is not always made clear on the label.
Right for commercial areas, high-traffic patios and anywhere that will see spills.
Epoxy
Hard, thick, chemical-resistant, and an interior product. Epoxy chalks and yellows badly under UV, so outdoors in Sydney it is the wrong choice unless it is being overcoated with a UV-stable topcoat.
Its place is the garage floor. If you are considering one, the preparation matters more than the product — see concrete cleaning for what has to happen to the slab before any coating goes near it.
What to use where
- Plain concrete driveway, coastal — silane-siloxane penetrating sealer
- Exposed aggregate you want to enhance — solvent-based acrylic, accepting the two to three year recoat
- Stencilled or stamped decorative concrete — acrylic, because the colour is the whole point
- Pool surround — penetrating, always. A film plus wet feet is a slip claim waiting to happen
- Garage floor — silicate densifier, or epoxy if you want the finish
- Commercial or high-traffic paved area — polyurethane
- Heritage or sandstone-adjacent work — penetrating only, and read our note on sealing sandstone first
The preparation is most of the job
Sealer failures are overwhelmingly preparation failures, not product failures.
The slab has to be properly clean. Any oil, tyre rubber, efflorescence or organic growth left behind becomes a place where the sealer does not bond, and on a film-forming product that shows up as a patch of peeling within a year.
It has to be dry. Most sealers want several days of dry weather after washing, and sealing a slab that still holds moisture is the classic cause of a milky, blushed finish. Fixing that means stripping and starting again.
It has to be the right temperature. Sealing in the middle of a Sydney summer afternoon on a slab in full sun will flash the solvent off before the product levels.
And a new slab needs to cure first — generally 28 days, longer for a penetrating sealer to work properly.
If the concrete is stained before you start, sealing locks the stain in permanently. Oil and rust both need to come out first.
Does it need sealing at all
Not every slab does. Plain structural concrete in a sheltered position, inland, with no decorative finish, will do fine unsealed for decades.
The case for sealing is strongest where there is salt exposure, where the finish is decorative and worth protecting, where spills are likely, or where the slab is porous enough to stain readily. For everything else it is optional maintenance rather than necessary protection.
If you want a straight answer on your own slab, we quote concrete sealing with the surface assessment included, and we will tell you when the honest recommendation is to leave it.
