EPDM Bonding & Adhesives

FAQ’s relating EPDM adhesives and bonding

  • Is one-sided application of the membrane sufficient?
  • Can the adhesive be left too long to flash off?
  • What are the coverage rates for the adhesives?
  • Which substrates can I adhere the membrane to?
  • Can the membrane be adhered onto a wet surface?
  • Must the roof surface be cleaned before adhesion of the membrane?

Is one-sided application of the membrane sufficient?

You should always apply bonding adhesive to both surfaces – roof deck (or board) and membrane.

Water-based adhesive can be applied to either to the substrate only (wet mate method), or using the two-sided contact method, i.e., both to the underside of the membrane and the substrate.

Can the adhesive be left too long to flash off?

Yes. The surfaces will be ready to be mated together after the adhesive is applied and has flashed off. If the prepared surfaces are left open longer than necessary, debris may contaminate the surface area, or temperature fluctuations may impair application.

Moisture can also have a detrimental affect to the performance of the adhesives if the prepared surfaces are left for too long.

What are the coverage rates for the adhesives?

Approximate figures are as follows:

  • Bonding adhesive is 2 sq. metres per litre.
  • Water-based adhesive (two-sided application method) is 2 sq. metres per litre.
  • Water-based adhesive (one-sided wet mate method) is 3 sq. metres per litre.

Which substrates can I adhere the membrane to?

EPDM membrane can be adhered to different substrates, such as OSB3 sterling board or plywood timber. Smooth concrete and tissue-faced insulation boards are also suitable, but note that new concrete should be fully cured before membrane installation and this typically takes a minimum of 28 days in the UK.

The membrane can be adhered normally on a timber overlay or insulation board, once mechanically fixed through asphalt into the roof deck. The membrane can then be adhered normally on these boards.

Installing the membrane over an existing asphalt surface is not recommended. To effectively waterproof directly onto an asphalt surface, consider the use of liquid waterproofing systems. Read more about liquid waterproofing.

Can the membrane be adhered onto a wet surface?

No. The surface of the roof deck must be fully dry and free of ponded water, snow, frost and ice before installation of the membrane can take place.

Attempting to adhere to a wet or even damp surface could lead to installation problems and likely failure of the application altogether. Please refer to the resource document ‘Roof Preparation’ for more information.

Must the roof surface be cleaned before adhesion of the membrane?

Yes. The surface of the roof deck must be swept clean, and be free of sharp and/or loose particles, fasteners, debris and/or foreign materials that could puncture the membrane.

The deck must also be free of substances such as oil, grease, bitumen residue and other contaminants before application can take place.

Preparation of the roof deck is possibly the most critical step.