Everything You Need for an EPDM Roof Installation

If you’re installing an EPDM roof on a garage, extension, garden room or dormer, getting the materials right from the start will save time, prevent leaks, and avoid costly call-backs.
This guide breaks down exactly what you need for a complete EPDM flat roof installation — whether you’re a DIYer or a roofing contractor.

1. One-Piece EPDM Membrane

A one-piece EPDM membrane is the foundation of the system. Unlike traditional felt, EPDM comes in large sheets, meaning:
• Fewer joints
• Faster installation
• Lower leak risk
• 70 year life expectancy
For most residential roofs, ordering a membrane cut to size reduces waste and speeds up fitting.
Pro Tip: Always allow the membrane to relax for 30-60 minutes before bonding.

2. Adhesive Types (Deck & Perimeter)

There are typically two adhesives required:

Water-Based Deck Adhesive

Used for bonding the membrane to timber decking across the main field area.

• Easy to apply with roller
• Ideal for OSB3 or plywood
• Low odour

Contact Adhesive (Perimeters & Upstands)

Used on edges, vertical surfaces and detailed areas such as upstands and parapet walls.

• Strong instant bond
• Required around trims and kerbs
• Essential for wind resistance

Important: When applying contact adhesive, you must allow the adhesive to become touch dry before bonding the EPDM membrane to the surface. Apply adhesive to both the substrate and the back of the rubber (where required), wait until it is dry to the touch (not wet or stringy), and then carefully bring the two surfaces together. Bonding too early can cause bubbling, poor adhesion and long-term failure.

Skipping the correct adhesive is one of the most common causes of failure.

3. EPDM Primer

Primer is required when installing:

• Flashing Tapes
• Seams
• Drain outlets

It prepares the rubber surface to ensure tapes and accessories perform correctly.

Without the use of primer, will result in failure. detailing will fail.

4. Edge Trims & Wall Flashing Trims

Trims aren’t just cosmetic — they:

• Secure the membrane edge
• Protect against wind uplift
• Direct water into gutters
• Provide a clean finish

Common residential trim types include:

• Drip trims
• Kerb/upstand edge trims
• Wall Flashing Trims (for wall abutments)

Getting trims right is essential for long-term performance.

5. Drainage Outlets

Flat roofs must drain correctly to avoid ponding water.

Depending on your setup, you may need:

• Internal rainwater outlets
• Parapet wall outlets

Outlets are joined to the membrane using primer and tape to create a watertight seal.

Poor drainage = premature roof failure and water ingress.

Optional (But Recommended) Extras

To ensure a professional result, consider:

• Jointing tape
• Corner patches
• Sealant
• Insulation boards (for warm roof builds)
• Vapour Control Layer (if insulating)

If you’re building a warm roof system, remember the correct layer order:
Deck → VCL → Insulation → EPDM

EPDM Installation Checklist

✔ One-piece EPDM membrane
✔ Water-based deck adhesive
✔ Contact adhesive
✔ Primer
✔ Edge trims
✔ Drainage outlet
✔ Tapes & detailing accessories

Why Choose EPDM for Residential Flat Roofs?

• Long lifespan
• Low maintenance
• Flexible in cold weather
• Clean, modern finish
• Ideal for DIY and trade

For garages, home extensions and garden rooms, EPDM remains one of the most reliable and cost-effective flat roofing solutions available.