Concrete is tough but unpredictable. It’s porous, alkaline and can hold moisture long after it looks dry. Ignore these factors and the coating can peel, bubble or lift away from the surface entirely. Once that happens, fixing it usually means grinding back and starting over.
After more than 65 years of making specialist coatings for Australian conditions, we’ve seen the same avoidable errors time and again. If you’re in the process of painting concrete or selecting floor paint for concrete floors, steer clear of these common mistakes to save time, money and frustration.
Errors when painting concrete: key takeaways
- Skipping moisture and pH checks — Moisture and high alkalinity weaken adhesion and cause bubbles or peeling.
- Poor surface preparation — Dust, laitance and contaminants stop coatings bonding and lead to early failure.
- Choosing the wrong primer — A mismatched primer can trap solvent, fail to penetrate or let layers shear apart.
- Using paint not made for concrete — Wall or trim paints can’t handle concrete’s movement, moisture and wear.
- Rushing recoat and cure times — Coats that don’t bond or cure fully lead to soft, weak films and costly rework.
Mistake 1: Skipping moisture and pH checks
Concrete may appear dry, but it can retain a surprising amount of moisture long after it has been poured. It’s also naturally alkaline, which can attack specific binders before they’ve cured. When you paint straight over a slab that’s still wet, you risk blisters, bubbles and whole sheets of coating lifting.
Efflorescence, the white, powdery salt you sometimes see, is an early sign of moisture movement. It means water is moving through the slab, carrying salts with it and undermining adhesion.
How to avoid it
- Test before you paint.
- A simple surface pH test shows if the slab is still too alkaline; most systems need it close to neutral (around 10 or lower).
- Use a moisture meter or in-slab probe to gauge dryness. If the readings are outside spec, wait or choose a moisture-tolerant system such as an epoxy barrier primer.
Mistake 2: Poor surface preparation
Good adhesion starts with what you do before opening the tin. Many failures come from rushing prep or assuming “it’s just concrete, it’ll stick.”
The surface may be coated in laitance, a weak, chalky layer left from curing. There could also be oils, grease or adhesive residues that stop paint from wetting in. Old coatings might look solid, but fail once new layers shrink and pull. When these contaminants remain, the new finish will flake, fisheye or telegraph every defect.
How to avoid it
- Mechanically prepare the slab. Diamond grinding or shot blasting removes weak layers and gives the surface a profile your coating can grip.
- Clean off oils or adhesives properly and don’t just mop and hope. Vacuum thoroughly, as dust is a silent bond breaker.
- If an existing coating is unsound or incompatible, remove it rather than bury the problem.
Mistake 3: Choosing the wrong primer
Concrete is not a single, predictable surface. A new slab may be porous and dusty, while a polished retail floor can be dense and slick; older sites often have remnants of previous coatings. Each condition changes how a primer needs to behave. There is no single primer that suits all of them.
The real job of a primer is more than sticking down dust. It balances porosity, so topcoats don’t soak in unevenly, ties the system to the slab and in some cases acts as a moisture or vapour barrier. Picking one made for timber, metal or generic walls won’t solve those problems and usually causes new ones.
How to avoid it
- Match the primer to the slab and conditions. A penetrating acrylic ties up dust and evens absorption on porous concrete.
- Where moisture levels are borderline, a moisture-tolerant epoxy barrier can effectively seal the surface.
- Dense, burnished or previously coated slabs need an adhesion-promoting primer after abrasion. And if the floor will cop UV or weather, use a primer that’s compatible with a UV-stable topcoat.
- Timing matters too. Primers have a recoat window where the next coat chemically bonds. Miss it, and you’ll need to sand or abrade before continuing.
- Apply the correct film build, as too thin and it won’t consolidate; too thick and it can trap solvent.
Mistake 4: Using paint not made for concrete
It goes without saying that concrete behaves nothing like plasterboard, timber or metal. Products made for walls or trim often lack the proper binders or film build to withstand the pressure.
The mistake usually occurs when someone wants to save time or use what’s already on hand, such as leftover interior wall paint, a tin of exterior house paint or a trim enamel from another job. These coatings are fine for their intended surfaces, but fail quickly on concrete.
Furthermore, floors need coatings built for heavy wear. Floor paints for concrete floors are formulated to withstand traffic, moisture and slab movement while resisting hot tyres, cleaning chemicals and UV.
How to avoid it
- This obvious problem has an equally obvious solution: choose a system made specifically for painting concrete.
- Look for coatings that mention concrete or masonry use on the label, and always check the technical data sheet for compatibility with alkaline and porous surfaces.
- Match the product to the exposure (indoor, outdoor, heavy traffic, chemical contact) rather than relying on any spare paint in the shed.
Mistake 5: Rushing recoat and cure times
Every coating system has a window where the next coat bonds. Paint too soon, and solvent from the first coat gets trapped, creating bubbles or weak spots. Paint too late and the surface needs sanding to avoid intercoat failure. Letting people or vehicles on the floor before a full cure risks scuffing and tyre pickup.
This mistake often comes from schedule pressure. Jobs are booked tight, spaces need to reopen or bad weather pushes work into a shorter window. It’s tempting to squeeze coats closer together or allow use before the film has hardened. The problem is that coatings cure through a chemical reaction, not just by drying to the touch. Disturbing them too early leaves a weak link between layers and a soft surface that fails under traffic.
How to avoid it
- Plan enough time for the full system, not just the application.
- Check the technical data sheet for recoat and service cure times and build them into the schedule before starting.
- If deadlines are strict, use products formulated for faster recoat or return-to-service, rather than cutting corners on cure.
Set your project up to last
As we’ve explored in this article, most failures around painting concrete are caused by poor preparation and rushing the job. Take the time to diagnose, prepare and apply correctly and your coating will last.
Viponds has been making specialist paints in Australia since 1954. We know local slabs, weather and traffic loads, and we provide clear TDS and SDS for every product. If you’re painting concrete and want a finish that holds, speak with our technical team. We can recommend the right system and floor paint for concrete floors, so you only do the job correctly the first time.