Roof waterproofing for PUR roof spray foam with liquid plastic

Flat roof waterproofing with old foam in full reinforcement

PUR roof spray foam, also known simply as PUR foam or PU foam, is a high-quality material for "roof-sealing thermal insulation". Foamed roofs are durable and, because of their excellent structural-physical properties, offer building owners reliable thermal insulation and waterproofing of their roofs with the greatest possible comfort of use.

The weak point with old foam is UV protection. Rigid polyurethane foam for roofs must be protected against UV exposure. In the early days of spray foam technology, products were designed for UV protection for a period of about 5 years. As a result, the protective measures had to be carried out again at relatively short intervals.

For this type of flat roof waterproofing, the use of liquid plastic with fleece insert in full reinforcement has proven to be a long-term solution.

Liquid plastic in full reinforcement

Advances in technological development have not stopped at UV protection products. Our coating Purelastik, a liquid plastic of the latest generation, has proven to be particularly durable in the renovation of old, weathered foam roofs. It has been shown that simply renewing the UV protective coating on old PUR roof spray foam does not produce the desired result. The solution: Liquid plastic with fleece insert in full reinforcement

In the case of full reinforcement, a technical fleece is inserted into the still liquid plastic and recoated until it is completely saturated. On average, the material requirement is 3 kg/m² . This produces a film on the roof that is seamlessly bonded to the substrate everywhere. With old foam, it must always be assumed that there is initial moisture in the substrate. This can escape via diffusion, the insulating foam becomes dry again and fulfills its insulating function.

Why roof waterproofing with old foam in full reinforcement?

PUR roof spray foam is not UV resistant. When the UV protection has weathered off, the foam absorbs water. This can then lead to the stored water freezing in winter at temperatures below 0°C, destroying the cell structure. This results in cracks in the surface, which can continue to the substrate. But even barely visible hairline cracks promote further water absorption. To prevent further water absorption, the surface must be protected with a stable coating. Purelastik liquid film is reinforced here with a fleece insert.

Together with the fleece insert, the Purelastik liquid plastic forms a stable film that is friction-locked to the substrate everywhere. In addition to reliable waterproofing, full reinforcement also offers a significant improvement in mechanical load-bearing capacity. With full reinforcement, special care is taken to ensure that roof penetrations, roof inlets and connections to rising building parts and parapets are reliably integrated into the surface.