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Can EPDM Be Laid Over Existing Roof Coverings?

Each EPDM membrane roofing system can be bonded to a range of different surfaces. This article covers the various do's and don'ts for each roofing system, the surfaces that can be bonded to and the adhesives required.

Full Answer

If you plan to leave your existing roof covering in place and install a new waterproof membrane over the top you will need to consider the following:

ROT - If the existing roof deck and supporting timbers are rotten these will need to be removed and replaced. OSB3 or exterior grade plywood are both good deck materials for bonding the new waterproof membrane to.

UPGRADE INSULATION - Whilst you are carrying out work on your roof it might be a good time to install a new warm deck insulation. If the existing roof deck is in good order then in most cases the existing waterproof layer such as felt can be left in place and the new insulation bonded over the top using PU adhesive or mechanically fixed using screws and washers. The new waterproof membrane can then be bonded to the insulation.  

We have listed below the preferred bonding surface for each of our EPDM systems along with the most appropriate adhesive. You will notice that the fleece backed DuoPly™ and bitumen backed RESITRIX® systems are more versatile. This is not an exhaustive list so if you dont find what you are looking for give us a call and we will do our best to help!

 

ClassicBond® & ShedCover System

Non-reinforced EPDM

Bonding Surface Adhesive
Timber under 100sqm Water Based Adhesive
Timber over 100sqm Contact Adhesive or Spray Contact
Glass Contact Adhesive or Spray Contact
GRP Contact Adhesive or Spray Contact
Metal Contact Adhesive or Spray Contact
Tissue Faced Insulation  Contact Adhesive or Spray Contact
Felt or Asphalt Not Recommended

N.B. Upstands and perimeter are always bonded with contact bonding adhesive or spray contact

DuoPly™ System

Fleece Backing

Bonding Surface Adhesive
Timber (Any Sized Roof) Water Based Adhesive
Glass PU Adhesive or Spray Contact
GRP PU Adhesive or Spray Contact
Metal PU Adhesive or Spray Contact
Tissue Faced Insulation PU Adhesive or Spray Contact
Felt or Asphalt PU Adhesive or Spray Contact

N.B. Upstands and perimeter are always bonded with contact bonding adhesive or spray contact

RESITRIX® System

Self Adhesive Bitumen Compatible

Bonding Surface Adhesive
Timber (Any Sized Roof) FG35 Primer
Glass FG35 Primer
GRP FG35 Primer
Metal FG35 Primer
Tissue Faced Insulation FG35 Primer
Felt or Asphalt FG35 Primer

N.B. Upstands and perimeter are bonded in the same way using FG35 Primer