Frequently asked questions about roof renovation with liquid plastic
Flat roof - Industrial roof - Foil roof - Garage - Bungalow - Permanently waterproof

• A one-component, water-based liquid plastic based on polymer dispersions

• Plasticizer-free, solvent-free, and highly elastic – ideal for bridging cracks

• After drying, it forms a seamless, self-adhesive sealing membrane Purelastik is a high-quality, durable, and easy-to-apply liquid plastic for sealing and protective coatings, especially on surfaces and roofs. Its strengths lie in the combination of UV resistance, crack bridging, durability, and ease of use, making it ideal for both professionals and ambitious DIYers. Key advantages: Vapourable: flexible at temperatures from -30°C to +100°C Waterproof: does not swell in standing water – thanks to high-quality mapping and fleece reinforcement Easy application: with roller, brush, broom, or airless sprayer – also suitable for DIYers Cleaning with water is possible. Low odor during processing – no plasticizers or solvents. No overlaps, mechanical fixings, or special heat welding equipment are required – ideal for detailed connections. Highly elastic and crack-bridging. Weather and UV resistant – expected service life of >25 years with full reinforcement.

At Pur-Protect, the term "full reinforcement" refers to a specific flat roof renovation technique. Full reinforcement describes the application of a liquid plastic waterproofing membrane in combination with a reinforcing fleece across the entire roof surface.

The fleece is embedded seamlessly and completely within the first layer of liquid plastic – this is known as "wet-on-wet" application.

This method is carried out using our high-quality PURelastik liquid plastic. Full reinforcement significantly increases the stability and longevity of the roof. This continuous reinforcement layer effectively prevents cracks and potential weak points, which is particularly important for flat roofs, whether sloped or level.

Full reinforcement protects the roof surface from the elements and ensures a durable seal, thus reducing the cost and effort of repairs in the long run.

1. Cleanliness

The substrate must be free of dust, grease, oil, and dirt.

Loose particles, moss, algae, or old coatings must be completely removed.

2. Dryness

The substrate must be dry.

On flat roofs, standing water must be removed before application.

Small amounts of residual moisture are acceptable, but no wet surfaces or water films are permitted.

3. Load-bearing capacity

The substrate must be firm, stable, and load-bearing.

Flaking old coatings or loose layers must be removed or repaired.

4. Suitable substrate materials

Concrete, screed, wood, metal, bitumen sheets (sanded and unsanded), old polyurethane foam coatings, tiles, etc.

For smooth or non-absorbent substrates (e.g., glass, tiles, metal), a primer (e.g., PURGRUND) should be used.

5. Pretreatment / Priming

Absorbent substrates (e.g., concrete, screed, wood) do not require a special primer but should be prepared (cleaned and, if necessary, slightly dampened).

Non-absorbent substrates or existing coatings: Primer is recommended, e.g., PURgrund from Pur-protect.

Bitumen sheets can be applied directly if they are properly adhered and clean.

Important additional information:

Application temperature: at least +5°C, ideally above +10°C

Humidity: not exceeding 80% during application

Substrate temperature: at least 3°C ​​above the dew point to prevent condensation

For slopes below 3% (where standing water is possible): full reinforcement with fleece is absolutely essential!

According to test reports, the expected service life of PURelastik liquid plastic is at least 25 years when the system is applied correctly – especially with full reinforcement using nonwoven fabric.

Service Life Classification:

The product has been tested according to ETAG 005 (European Technical Approval for liquid plastic waterproofing systems) and achieves service life class W3.

👉 This means: ≥ 25 years service life with proper application.

Weather and UV Resistance:

PURelastik liquid plastic is specifically designed for long-term outdoor use, including high resistance to UV radiation, rain, frost, heat, and temperature fluctuations from -30 °C to +100 °C.

Waterproofness:

With the correct layer thickness and the use of the appropriate nonwoven fabric, PURelastik liquid plastic remains permanently watertight, even in standing water.

Mechanical Resistance:

In roof applications or under light stress, the layer remains intact for a long time. For balconies or walkable areas, an additional wearing layer (e.g., paving slabs or wooden decking) is generally recommended to protect the waterproofing.

Application of PURelastik liquid plastic:

(Suitable for flat roofs, balconies, terraces, connections, and detailing)

1. Substrate preparation

The substrate must be:

Clean, dry, and load-bearing

Free of dust, oil, grease, moss, and loose particles

Suitable substrates:

Concrete, screed, wood, metal, bitumen sheets, foil, polyurethane foam, existing PURelastik coatings, and tiles

👉 Note:

Non-absorbent substrates (e.g., metal, tiles) must be pre-treated with a suitable primer (e.g., PURgrund).

2. Primer (if necessary)

When?:

Smooth, non-absorbent surfaces

Old coatings with poor adhesion

👉 Product: PURgrund from PUR-protect

👉 Primer drying time: approx. 30–60 min

3. Laying the reinforcing fleece (full reinforcement recommended)

1. Apply a generous coat of PURelastik.

Lay the reinforcing fleece (PUR-protect reinforcing fleece) in place, ensuring it is free of air bubbles.

Immediately apply another coat of PURelastik from above until the fleece is completely embedded.

Fleece overlap: approx. 5–10 cm

👉 Why full reinforcement?

Increases service life, improves crack bridging, and is essential for a service life of ≥ 25 years.

4. Applying the Main Coat

After the first coat has dried (approx. 4-6 hours, depending on weather conditions), apply a generous coat of PURelastik liquid plastic.

Total coating thickness: at least 2.1 mm.

Application is possible with a roller, brush, or airless sprayer.

👉 Note:

Do not apply coatings thinner than 2.1 mm – otherwise, long-term waterproofing cannot be guaranteed.

5. Drying Times

Skin Formation: approx. 1 hour at 20 °C

Rainproof: approx. 4–6 hours (approx. 30 minutes possible with Speedcat Rainproofing Aid)

Full Drying Time: approx. 12 hours per coat

Fully Load-Bearing: after approx. 7 days

6. Application Conditions

Temperature: +5 °C to +35 °C

Humidity: max. 80%

Substrate Temperature: at least 3 °C above the dew point (no condensation!)

Do not apply in rain or frost.

We recommend light gray (RAL 7035) for roofs. During colder seasons (autumn) with lower UV radiation, we also use slate gray (RAL 7015) as a first coat, as the darker color allows the liquid plastic to heat up and dry more quickly. We then usually apply light gray (RAL 7035) as the final coat.

PURelstik liquid plastic is also available in white.

Andere Farben sind auf Anfrage lieferbar.

Die Vorteile einer hellen Dachabdichtung:

1. Geringere Aufheizung

• Reflektieren bis zu 80 % der Sonneneinstrahlung.

• Dachtemperaturen im Sommer: ca. 30–40 °C, schwarz 80 - 90 °C) .

• Reduziert die Materialausdehnung und Spannungen.

2. Besserer sommerlicher Wärmeschutz

• Senken die Raumtemperatur unter dem Dach.

• Reduzieren den Bedarf an Klimaanlagen.

3. Energieeinsparung

• Geringerer Stromverbrauch für Kühlung.

• Nachhaltige Betriebskostenersparnis.

4. Schutz der Dachkonstruktion

• Weniger thermische Belastung.

• Geringere Materialermüdung und längere Haltbarkeit.

5. Ökologische Vorteile

• Cool Roof Effekt: Reduziert lokale Hitzeentwicklung in Städten.

• Positiver Beitrag zur Eindämmung des Klimawandels.

6. Längere Lebensdauer

• Weniger Temperaturschocks.

• Geringere Alterung durch Hitze.

Yes, PURelastik liquid plastic is comparable to conventional membranes as a roof waterproofing material, but offers additional advantages that set it apart from traditional materials.

Unlike conventional membranes, PURelastik is characterized by its seamless application, which ensures a continuous and uniform seal. This reduces the risk of leaks and cracks that can occur with welded or glued membranes. PURelastik liquid plastic offers high elasticity and resistance to extreme weather conditions, making it ideal for flat roofs, with or without a slope. Furthermore, the liquid plastic is particularly adaptable and can be easily applied to complex roof structures and challenging substrates. This flexibility allows for quick and efficient renovation, often resulting in lower labor costs and a longer roof lifespan.

Pur-Protect specializes in the renovation of flat roofs using liquid plastic and PUR roof spray foam, employing state-of-the-art technologies to achieve the best results. If you are looking for a reliable and durable sealing solution, PURelastik liquid plastic from Pur-Protect offers an excellent alternative to conventional roofing membranes.

Yes, Pur-Protect's innovative solution with PURelastik liquid plastic can effectively renovate a damp, old foam roof! However, an individual approach is required after a preliminary assessment, possibly including the installation of flat roof vents, depending on the degree of dampness.

Our specialized technology offers a seamless, waterproof seal specifically designed for the renovation of old foam roofs. Thanks to the outstanding elasticity and lasting weather resistance of PURelastik liquid plastic, it protects your roof from further water damage and extends the lifespan of your old foam roof. Our experts are highly familiar with the unique challenges of damp, old foam roofs and employ state-of-the-art methods to restore them to optimal condition.

Trust Pur-Protect's expertise for sustainable roof renovation!

Yes, PURelastik liquid plastic can be used to seal balconies and terraces – in fact, it's very well suited for this purpose. Thanks to its elastic and seamless properties, the liquid plastic offers many advantages in these applications.

However, there is one limitation: if tables, chairs, or other furniture are placed on the surface and it is frequently used and walked on, then it is necessary to protect the coating with wooden boards, patio slabs, paving stones, or similar materials. The coating remains permanently elastic and would be damaged by excessive point loads.