What is polyurea?
Polyurea is a two-component plastic applied as a seamless sprayed layer. The two parts — an isocyanate and an amine resin — react with each other extremely fast: the layer gels within seconds and is usually walkable within an hour.
The result is a membrane that is waterproof, highly elastic and very wear-resistant, with no seams, laps or welded joints.
Properties
- Seamless. The membrane follows every shape: corners, penetrations, outlet rims and upstands are taken in one pass. Those are precisely where traditional sheet systems leak.
- High elongation. Polyurea can stretch by many tens of per cent and therefore bridges moving cracks, provided the system has been selected for that.
- Wear and impact resistant, including under traffic loading.
- Chemically resistant to many salts, de-icing agents and dilute chemicals.
- Very fast cure, also at low temperature and even in frost — a real practical advantage in the winter season.
Applications
- Car park decks and ramps, where waterproofing, wear resistance and crack bridging are needed at the same time.
- Roofs and roof terraces, especially where there is a lot of detailing.
- Basements, tanks, sumps and ponds.
- Channels and bunds with a chemical exposure.
- Balconies and access decks in refurbishment, where a thin, light layer is wanted.
- Protective coatings on concrete, steel, timber and EPS shapes.
Points to watch
- This is not DIY work. Polyurea is applied with heated two-component high-pressure equipment that only mixes the components at the spray gun. It is specialist work for a certified applicator.
- No correction time. Because it gels in seconds, you cannot touch in, level out or brush over. A spray fault stays visible in the surface.
- The substrate decides everything. Concrete must be sufficiently dry, dust-free, ground or blasted, and primed. The overwhelming majority of failures come down to preparation and primer choice, not to the membrane.
- Moisture during spraying. Isocyanate reacts with moisture. Condensation on the substrate or excessive humidity causes blistering.
- UV. Standard aromatic polyurea discolours and chalks under UV. That is cosmetic rather than structural, but on exposed work an aliphatic topcoat is needed.
- Occupational health. Isocyanates are involved. Respiratory, skin and eye protection and screening of the surrounding area are mandatory; in the EU, professional use of products containing diisocyanates additionally requires documented training.
- Cost. Expect a clearly higher rate per square metre than a bituminous or single-ply membrane. The value lies in complex detailing, short programme and long service life — on a large, plain roof with few details that advantage is small.
Related terms
- Polyurethane
- Floor coating
- Waterproofing
- Car park deck
- Primer
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.