Concrete and flat roof — EPDM
EPDM (ethylene propylene diene monomer) is a flexible synthetic-rubber waterproofing membrane used on low-slope roofs. On concrete, the specified assembly may include substrate repairs, vapour control, insulation/cover board, membrane, edge terminations, and drainage.
- Prepare the substrate: Confirm concrete is sound, clean, dry, and suitable for the system; repair defects and confirm drainage falls.
- Install the membrane: Lay EPDM and secure it using the approved adhesive, mechanical attachment, or ballasted method.
- Detail seams and edges: Prepare seams as required by the membrane system and carefully finish parapets, corners, outlets, and penetrations.
- Inspect and maintain: Check terminations and seams, keep drains clear, and protect the membrane from punctures.
Common risk areas: Poor seam preparation, loose edge details, punctures, badly sealed penetrations, trapped moisture, and inadequate drainage. EPDM seams are typically primed and taped—not heat-welded like TPO or PVC.
Waterproofing at a wall/base junction.
Dark membrane installed across a flat roof.
Membrane upstand along the wall junction.
