Why Two Different Adhesives Are Essential for Installing an EPDM Rubber Roof
You may be curious why two types of adhesives are recommended when installing an EPDM rubber roof. The answer lies in the fact that your roof will face a variety of temperatures and weather conditions throughout its lifespan. Standard off-the-shelf adhesives simply don’t offer the long-term durability needed to maintain the integrity of an EPDM roof, which can last up to 50 years.
To meet this challenge, two specialised adhesives have been designed: Water-Based Deck Adhesive (WBA) and Contact Adhesive. Both are engineered to ensure long-lasting performance, but each plays a distinct role in the installation process.
Understanding the Difference in Application
- Water-Based Deck Adhesive (WBA) is used across the main deck area of the roof.
- Contact Adhesive is applied around the perimeter (typically within 150mm of the edges) and on upstands, where a stronger grip is essential.
Let’s explore the pros and cons of each adhesive to understand why both are crucial for a secure, durable EPDM roof installation.
Water-Based Deck Adhesive: The Foundation of Your Roof
Water-based deck adhesive forms the key foundation of any EPDM roofing project. Its user-friendly application and extended drying time offer the flexibility needed for precise adjustments during installation.
Pros:
- User-Friendly Application: Specially formulated for easy roller application on flat roof surfaces.
- Adjustability: Longer drying time (temperature-dependent) allows for repositioning the membrane before it becomes tacky, offering greater control.
- Solvent-Free: Provides strong adhesion without using solvents, making it an environmentally friendly choice.
- Versatile: Perfectly suited for flat timber roofs, such as OSB3 or plywood (untreated)
Cons:
- Temperature Sensitivity: Not recommended for use when deck temperatures drop below 5°C, as this can affect bonding strength.
- Longer Curing Time: While beneficial for adjustments, the extended drying time can slow down the installation process, especially in cooler or damp conditions.
- Surface Limitations: Best suited for flat, porous surfaces like timber; not ideal for non-porous or vertical applications.
- Moisture Sensitivity: Performance may be compromised if exposed to moisture before fully cured.
- Less strength: Water-based deck adhesive is less firm and gripping than contact adhesive, making it less suitable for high-stress areas, like skylight upstands & parapet walls.
Contact Adhesive: Unrivalled Strength for Edges & Details
Contact adhesive is essential for securing EPDM rubber around roof perimeters and upstands, where maximum strength and a firm anchorage are critical. This high-strength, solvent-based adhesive is designed to withstand extreme temperatures, ensuring the EPDM membrane stays firmly in place for decades.
Pros:
- Superior Bonding Strength: Delivers maximum adhesion with an instant, strong grip.
- Versatile Compatibility: Suitable for a range of surfaces, including timber, brickwork, metal, PVC, and concrete.
- Durability: It withstands harsh weather conditions, especially wind uplift, and supports the EPDM membrane’s longevity of up to 50 years.
- Large Roof Support: Essential for roofs over 100m², helping to minimise expansion and contraction of the EPDM rubber.
Cons:
- Limited Adjustment Time: Once bonded, repositioning the EPDM is challenging due to the adhesive’s strong, immediate grip.
- Tack Time Required: It needs 5 to 10 minutes to become tacky before bonding, which can add time to the installation process.
- Challenging Application: The need for double-sided application and a shorter tack time make this adhesive more demanding to work with than WBA, particularly on larger surfaces.
- Temperature Sensitivity: Best applied at temperatures of 4°C and rising. While it may work at 1°C, optimal performance is ensured at higher temperatures.
Conclusion
Water-Based Deck Adhesive and Contact Adhesive are essential for any successful EPDM roof installation. Water-Based Deck Adhesive provides a strong foundation with the flexibility for adjustments, making it crucial on all projects under 100m². Contact Adhesive ensures that the EPDM membrane is securely anchored around the perimeter and upstands, where extra bonding strength and instant adhesion are critical.
Together, these two adhesives work in harmony to create a durable, weather-resistant roofing system that maximises the lifespan of your EPDM roof. Regardless of the complexity of your roof, both adhesives are necessary to ensure a long-lasting, high-performance installation.
Please note contact adhesive is not required for use with Skyguard's EPDM membrane. The Skyguard membrane caters for smaller outbuildings like sheds. The Skyguard Water-Based Deck Adhesive alone is very capable of providing the bonding strength required.
If you’d like to learn more or discuss your roofing project in detail, please don’t hesitate to contact us at Rubber4Roofs. Our skilled, professional team is here to provide expert guidance and help you choose the best solution for your specific needs.
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