Installing a flat roofing system isn’t something to rush. You’ll need a clear plan, the right tools, and a bit of patience to get it right. That’s where ClassicBond® EPDM membrane comes in. It’s flexible, easy to handle, and built to last for decades when installed correctly. The process starts with careful prep — cleaning the roof surface, setting trims, and bonding the membrane securely in place. Every step matters if you want a watertight finish. Skipping details can lead to leaks, wasted time, and costly repairs later. Simple things like letting the membrane relax before bonding, applying adhesives the right way, and sealing trims properly make all the difference. Key Takeaways Prep the roof surface and trims before laying the membrane. Apply adhesives with accuracy for a strong, lasting bond. Finish corners and edges properly to keep the roof watertight. The ClassicBond® EPDM membrane is a versatile roofing solution that works well across different types of flat roofs. When paired with Sure Edge® trims, it creates a clean, watertight finish that’s built to last. Overview of Classic Bond EPDM Membrane Trim Options You can choose from two types of Sure Edge® gutter trims: Standard trim — fixed to a 50 mm x 25 mm timber batten. Batten back plate — mounted directly onto the fascia, using a deeper PVC plate instead of timber. Installation Notes Fix trims with stainless steel ring shank nails. Leave a 1 mm expansion gap per meter between trim lengths. Allow the membrane to overhang about 75 mm past the roof edge (adjust if needed). Let the sheet relax for 30 minutes before bonding — longer or shorter depending on weather. Adhesive Use Water-Based Adhesive (WBA): Apply to timber decks. The surface must stay wet when laying the membrane. Bonding Adhesive: Use for non-timber decks and perimeter edges. Apply to both the deck and membrane, and let it tack off before joining. On large jobs (over 100 m²), reinforce the perimeter with a Reinforced Universal Securement Strip (RUSS). Finishing Details Broom the bonded membrane to remove air pockets and improve adhesion. Fix Sure Edge® trims with polytop nails through the pre-drilled holes. Ensure foam strips compress by 30–50% for a watertight seal. Staple corners if required, but always make sure they’re weathered. Corners and joining clips are fixed with plastic adhesive to allow slight movement. Components at a Glance Component Purpose Fixing Method Sure Edge® gutter trim Secures and finishes roof edge Polytop nails through pre-drilled holes Sure Edge® check curb Used where no gutter is present Polytop nails with foam seal RUSS strip Reinforcement on large roofs Bonding adhesive Preparation and Tools Required Before you begin, make sure you’ve got everything ready. Having the right tools and materials at hand makes the installation smoother and avoids mistakes. Tools & Materials Checklist Material / Tool Purpose EPDM membrane Main roofing layer Sure Edge® PVC trims (gutter + check curb) Finishing and edge securement Stainless steel ring shank nails Fixing back plates Polytop nails Securing trim plates Timber batten or PVC back plate Support for gutter trim Water-Based Adhesive (WBA) Deck bonding on timber surfaces Bonding adhesive Perimeter and non-timber deck bonding Broom Pressing membrane into adhesive Staples Securing corners when required Plastic adhesive Sealing corners and joining clips Tip: Always leave a 1 mm expansion gap per meter between PVC trim lengths. Preparing the Roof Surface Fix the gutter trim back plate to the fascia. Use either a timber batten or a deeper PVC back plate, depending on your project. Leave a 75 mm overhang of membrane around the edges (adjust if site conditions require). Allow the membrane to relax for about 30 minutes before bonding. In hot or cold weather, adjust this timing. If using WBA, leave a 100 mm perimeter clear for bonding adhesive. Skip this step if you’re using bonding adhesive everywhere. Apply adhesive while it’s still wet so it bonds correctly. Work in sections: pull the membrane back to the center, roll on adhesive, then lay it back in place. Broom the membrane down to remove air bubbles and improve adhesion. At the edges, apply bonding adhesive on both the deck and underside of the membrane. Let it tack off before pressing together. Once secure, fix the PVC trims with the supplied nails through the pre-drilled holes. Make sure the foam strip compresses by 30–50% for a proper seal. Trim away any excess membrane at the gutter, then attach corners and joining clips to finish. Installing Sure Edge Gutter Trim Picking the Right Back Plate The back plate fits to the fascia at the gutter edge and gives support for the gutter trim. You can choose between two types: Standard plate – fixed onto a 50 mm x 25 mm timber batten. Batten plate – mounted straight to the fascia with a deeper PVC option, no timber required. Both options provide a solid base for the trim and ensure the edge is secure. Fixing the Trim in Place Position the gutter trim front plate and fix it with polytop nails through the pre-drilled holes. The holes keep the spacing even. The foam strip compresses to form a watertight seal and pushes water over the trim. Cut away any excess membrane at the gutter edge. For corners, you can use staples if needed—but always make sure they’re tucked under the trim to stay weatherproof. Leaving Space for Movement PVC trims expand and contract with temperature changes. To prevent stress or cracks, always: Leave a 1 mm expansion gap per meter of trim length. Use corners and joining clips to connect sections. Apply a small amount of plastic adhesive on one side of each clip—this keeps joints secure while still allowing movement. Membrane Layout and Relaxation A smooth, flat membrane is key to a lasting roof. Overhang rules: Standard overhang: 75 mm all around. Non-gutter edges: at least 50 mm. Expansion gap: 1 mm per meter between trim runs. Corners: If stapled, ensure the staples are covered by trims so they stay dry. Foam strip: It should compress by 30–50% for a watertight seal. Time for Membrane to Settle Lay the membrane loosely over the roof. Let it relax for about 30 minutes (adjust for hot or cold conditions). Fold it back to the center and apply adhesive— Water-Based Adhesive (WBA) for timber decks. Bonding adhesive for non-timber surfaces. Lay the membrane into the adhesive while it’s still wet. Broom it smooth, working out air pockets as you go. Adhesive Application Techniques Applying Water-Based Adhesive (WBA) Let the membrane relax for about 30 minutes before applying the adhesive. Fold the membrane back to the center and spread the adhesive evenly across the deck. Coverage guide: leave a 100 mm band clear around the edges for perimeter bonding. Key step: lay the membrane into the adhesive while it’s still wet to ensure proper transfer. Use a broom to press out any air pockets and make sure the membrane sticks firmly. Repeat the process on the other side of the roof until the entire surface is covered. Applying Bonding Adhesive Bonding adhesive is used for non-timber decks and along roof edges. Apply adhesive to both the deck and the underside of the membrane. Let the adhesive tack off before pressing the surfaces together — this prevents blisters from trapped solvents. Work on opposite sides of the roof simultaneously for faster installation. This adhesive is also applied under trims and at roof edges for a watertight seal. Adhesive Transfer Tips Getting the glue to transfer correctly is critical. Make sure it moves properly from the deck to the membrane. Adhesive Type Application Surface Transfer Requirement Water-Based (WBA) Deck only Must stay wet for proper transfer Bonding Adhesive Deck + membrane Must tack off before joining Membrane Installation Process Positioning the Membrane Unroll the membrane so it extends past the roof edges, aiming for 75 mm on all sides (adjust as needed). Let the sheet relax for about 30 minutes — adjust for hot or cold weather. Fold the membrane back to the center. Apply adhesive: Water-Based Adhesive (WBA) for timber decks Bonding Adhesive on both deck and membrane for non-timber surfaces Lay the membrane into the adhesive while it’s still wet for a strong bond. Using a broom to press the membrane helps eliminate air pockets and ensures even contact with the adhesive. Working in sections keeps the membrane aligned across the roof. Securing Contact and Removing Air Press the membrane firmly with a broom to remove trapped air. Work in sections and repeat on opposite sides for even coverage. Installers often tackle opposite sides simultaneously to speed up the workflow. Let bonding adhesive tack off before pressing down the membrane to prevent blistering. Minor blisters are usually temporary as solvents escape. Perimeter Trims and Expansion Fix trims using pre-drilled holes and supplied nails. Compress foam strips in trims to form a watertight seal. Leave a 1 mm expansion gap per meter between trim sections for movement. For large roofs (over 100 m²), add reinforced securement strips (RUSS) along the edges and use bonding adhesive across the deck for extra hold. Quick Reference Standard overhang: 75 mm Non-gutter edges: 50 mm minimum Expansion gap: 1 mm per meter Finishing Roof Perimeter Spreading Adhesive Around the Edges Apply Bonding Adhesive to both the deck and the underside of the membrane at roof edges. Let the adhesive tack off before pressing the surfaces together to allow solvents to escape. Work in sections and apply adhesive on opposite sides for better control and flow. Key points: Adhesive on both surfaces Wait for it to tack off before bonding Work in stages for more control Installing Perimeter PVC Trims PVC trims secure the membrane and give a clean, finished edge. Back plate first: attach to a timber batten or directly to the fascia with a deeper PVC option. Fix trims using stainless steel ring shank nails or polytop nails through pre-drilled holes. Leave a 1 mm expansion gap per meter between trim sections. Compress foam strips by 30–50% for a watertight seal. Nail gutter trim front plates and check curbs firmly in place. Trim options at a glance: Trim Type Installation Surface Fixing Method Seal Method Standard Trim Timber Batten Stainless nails Foam strip Batten Back Plate Fascia (no timber) Stainless nails Foam strip Gutter Trim Front Gutter edge Polytop nails Foam strip Check Curb Trim Non-gutter edges Polytop nails Foam strip Trimming Excess Membrane Trim away any extra membrane hanging past the roof edge, leaving a 50–75 mm overhang before cutting to size. At corners, staple the membrane if needed, ensuring staples are weathered before adding trims. Attach corners and joining clips, using a dab of plastic adhesive on one side to allow slight movement while keeping the perimeter sealed. Properly fastening corners prevents water from sneaking in around staples and keeps the roof edges tight. Installing Perimeter Check and Gutter Trims If there’s no gutter, install check trims along the roof edge. The membrane should extend at least 50 mm past the edge before trimming. Compress foam strips in the trims by 30–50% for a watertight seal. Nail trims through pre-drilled holes using supplied polytop nails. Leave a 1 mm expansion gap per meter between trim sections. Trim Options Quick Guide: Trim Type Placement Fixing Method Seal Method Gutter Trim Fascia with gutter Polytop nails Foam strip compression Check Trim Roof edge without gutter Polytop nails Foam strip compression Creating a Tight Seal Add joining clips and corner pieces at the perimeter. Apply plastic adhesive on one side to allow slight movement while keeping the joint sealed. For roofs over 100 m², install reinforced securement strips (RUSS) along edges for extra strength. Expansion Gaps Quick Reference: 1 m trim → 1 mm gap 2 m trim → 2 mm gap 5 m trim → 5 mm gap RUSS strips provide extra support on large roofs and, combined with bonding adhesive, ensure the membrane stays secure and resists shifting over time.
