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.
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.
UPGRADE INSULATION - Whilst you are carrying out work on your roof, it might be a good time to install 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. If you are deciding to insulate on top of the existing waterproof layer, you must bond the new insulation on 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 ClassicBond Pro and bitumen-backed Resitrix systems are more versatile. This is not an exhaustive list so if you don't find what you are looking for give us a call and we will do our best to help!
ClassicBond® & Skyguard 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 a contact bonding adhesive or spray contact
ClassicBond Pro™ 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 a 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
