Fully Adhered Application

Once the substrate is properly prepared, the EPDM membrane can be laid out onto the roof and positioned. Make sure enough membrane overhangs the roof perimeters and upstands, allowing it to be trimmed later.

When EPDM membrane is laid in situ, it can take around 30 minutes to relax. In cold weather conditions, this waiting time will be extended and any folds that are sometimes present in the membrane can take longer to dissipate.

The membrane is applied from the centre of the roof out towards the perimeter edges. At these edges and upstands, folds excess membrane back onto the roof. This ensures any wrinkles are removed, making the membrane easier to apply. Then fold the sheet back onto itself exposing approximately half of the roof substrate.

Applying adhesive to EPDM systems

Bonding of the membrane can now begin. Using a 9-inch roller, apply the water-based bonding adhesive to the timber substrate only.

Once the adhesive is applied, the membrane can be laid into it whilst still wet. Roll the membrane into the adhesive avoiding stress or wrinkles, taking care to spot and remove any debris that may have fallen onto the deck in the meantime.

Entrapped air and wrinkles can be removed by gently smoothing with a soft bristle broom, adding more pressure with each pass of the broom. Do not stretch the sheet.

Roll back the other half of the membrane until approximately 100mm of the already applied adhesive is visible and repeat the procedure.

Note that the water-based bonding adhesive does not go right up to the perimeter edge of the roof deck, but instead terminates 100-150mm away. This area is where the Bonding Adhesive will be applied later. The water-based adhesive can take up to a few hours to grab the membrane completely depending on ambient temperatures, but the use of the Bonding Adhesive around the perimeter edges secures the sheet in place during this period.

Important notes:

The above method of application relates to a timber deck (plywood or OSB) only. For direct application to other surfaces e.g. polyisocyanurate insulation board or concrete, Bonding Adhesive must be applied to BOTH this substrate and to the back of the membrane. Allow it to become tacky to a finger touch. The membrane can then be applied to the substrate. Broom the membrane surface to ensure sufficient contact of the membrane with the substrate.

Please also refer to “Weather Conditions” within the Roof Preparation section of this manual for appropriate application.

These upstands can be adhered using Bonding Adhesive later on.

A pipe penetration is dealt with in a similar way.

Once the membrane has been cut and laid around all obstruction, the rest of the bonding procedures can continue.

Important notes:

For fully adhered installations that are typically over 100 sq. m in area, base tie-in details are required for additional securement.

This procedure requires the addition if Reinforced Perimeter Fastening (RPF) strip, V-plates and All-Purpose fasteners to be attached at the upstand and perimeter edges.

For further details, please refer to the “Mechanically fixed application” section of the manual.

More guides from Permaroof

Permaroof UK Ltd offers support for EPDM application, whether for trade roofers or for the DIY market. The resource library contains an extensive range of EPDM installation guides in downloadable PDF format and video tutorials with step-by-step instructions given by qualified and experienced EPDM specialists.

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Become an expert with our EPDM training days

Permaroof UK Ltd runs EPDM training days for both sheet membrane application and liquid waterproofing. EPDM application training days are held weekly at the Permaroof headquarters in Derby at our purpose-built, approved training centre. Suitable for both trade and DIY flat roofers, the one-day courses offer industry-leading training and certification.

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