Polyurethane coatings directly on concrete is not a good idea.
I must say that polyurethane is a good coating for wood floors and timber. 
The problem started or became more common about 2005 when many floor sanders decided to become concrete floor grinders. They went out and bought grinders, started grinding floors and then thought “hmm what am I going to use to seal this floor?” They went back to their suppliers who were all too keen to sell them polyurethane.
Polyurethane floor coatings have some great properties.
- Polyurethane has high chemical resistance
- Polyurethane has good abrasion resistance
- Polyurethane bonds well to the fibre structure of timber.
BUT when it comes to a coating for concrete floors, polyurethane has some failings.
- Polyurethane generally does not bond well into the particle surface of concrete.
- Polyurethane usually suffers from moisture delamination.
- Most polyurethane coatings suffer when exposed to UV (yellow).
N.B. Polyurethane can be applied successfully over another resin (primer) – if it is within the recoat window or the coating has been fully scuffed/sanded for maximum adhesion. But be aware many other resins are not UV stable and will discolour if exposed to any UV light.
I know many people use polyurethane as a “term” for a sealer because it is a common word. But it would be better to say concrete sealer or concrete coating.
So what should you use?
Some other coatings that are much better suited to the granular nature of concrete are –
- Arcylic – the most common resin used in general concrete sealers is acrylic resin. There are solvent and water based acrylic resin concrete sealers.
- Epoxy – epoxy is better used indoors as most formulations can discolour with UV exposure.
- Polyaspartic – polyaspartic resin coatings offer fast install and higher abrasion resistance.
- Polyurea – (different to polyurethane) is similar to polyaspartic.
Different concrete sealers offer different benefits, performance and visual variations.
It is important to speak to us about your use of the floor and any factors that relate to wear, chemical exposure and visual preference.
Polyurethane is not suitable for direct application to concrete floors – talk to us about what would suit your purpose the most –
call us on 021 426627 or fill out out quote request form here
