How to protect PUR foam against UV radiation and water?

Closed-cell PUR foam is a very popular material used for insulating flat roofs from the outside. Application involves applying foamed polyurethane to the roof surface using a special spray gun. After spraying, the foam swells and hardens, achieving its final form. PUR foam has many advantages – it creates a continuous, homogeneous structure, eliminating any joints or thermal bridges. It is ideal for covering surfaces with unusual shapes, as spraying allows for reaching every nook and cranny, and provides excellent thermal insulation – the thermal conductivity coefficient (λ) for this material is 0.021-0.024 W/m·K.

However, PUR foam is not UV-resistant, so it cannot be used as a final coating on a flat roof. It should be surface-sealed with a suitable liquid waterproofing membrane that will block sunlight and resist any potential waterlogging.

Neoproof PU W-40 – single-component, water-soluble polyurethane membrane

Neoproof PU W-40 is a liquid polyurethane waterproofing membrane. Easy to apply – the product is water-soluble and single-component. It creates a tight, uniform coating. It can be applied with a traditional roller or spray. The coating is fully resistant to waterlogging and UV radiation. The elasticity of the cured coating is up to 250% (elongation at break at 3 MPa).

Before applying Neoproof PU W-40, prime the PUR foam with Revinex , diluted 1:4 with water. After 2 hours, apply the first layer of membrane. Then, 24 hours later, apply the second layer. Theoretical material consumption per square meter should be no less than 1.2 kg/m².

Neoproof Polyurea C1 – a two-component, solvent-based polyurea membrane

Neoproof Polyurea C1 is a modern, two-component polyurea waterproofing product for cold application. Unlike polyurea products applied with a special hot-melt unit, this membrane can be applied with a traditional roller or airless spray.

The product is two-component (base + hardener). Before application, the components must be combined and thoroughly mixed with a low-speed mixer. From this point, you have approximately 90 minutes (at 23°C) to use the product, after which it will harden and solidify. The elasticity of the cured coating is 410% (elongation at break, at a force of 9.8 MPa).

Similar to Neoproof PU W-40, we obtain a uniform, tight coating that is fully resistant to waterlogging and UV radiation. An additional advantage of this product is that it can withstand rain after just two hours! This is a crucial parameter in unpredictable weather conditions.

Other features that speak in its favor are:

• application directly on closed-cell PUR foam, without primer
• application in one layer (the "C1" in the name comes from the English "one coat")

These two factors result in faster completion of work – there is no need to return to the construction site to apply subsequent layers.

What if we are dealing with old PUR foam found at the construction site, painted with other coatings?

No problem! Most often, this will be one of the following situations:

• Old coating in good condition, requiring refreshing

Thoroughly wash the roof and allow it to dry. Neoproof Polyurea C1 directly, and Neoproof PU W-40 after priming the surface with diluted Revinex.

• The old coating is peeling, the PUR foam has been partially “eaten” by solar radiation or is mechanically damaged and has open cells.

In this case, we also thoroughly wash the roof and allow it to dry. Flaking fragments of the old coating will fall off. The foam in these areas will likely have open pores. In this case, we recommend choosing Neoproof Polyurea C1 , which we apply after priming these areas with Acqua Primer NP, .

Closed-cell PUR foam is a modern solution for roof thermal insulation. Combined with one of the liquid waterproofing membranes described above, it will provide excellent roof protection and peace of mind for years to come.