How to Apply Rubber Roofing Adhesive? | Full Step-by-Step

Rubber roofing adhesive is applied in two stages: water-based bonding adhesive for the main deck while wet, then contact adhesive for perimeters and vertical upstands.

Applying rubber (EPDM) roofing adhesive correctly requires two distinct steps, and mixing them up is the leading cause of installation failure. The main deck gets water-based bonding adhesive applied to both surfaces and rolled together while still wet, while perimeters and vertical upstands need a separate contact adhesive that dries until tacky before bonding. If you’re choosing which product to use, our roundup of the best adhesives for rubber roofing compares top-rated options for each stage of the job.

Preparing the Deck and Membrane

Start with a clean, dry roof deck — remove all dust, dirt, rust, oil, grease, and loose material. Every fastener must be secure and all sharp edges removed. Unfold the EPDM membrane and lay it loosely over the deck for at least 30 minutes so it can relax and shed wrinkles. Then fold the membrane back over itself (typically in half) to expose the deck. Johns Manville’s EPDM application guide stresses that the surface must be fully dry and contaminant-free before any adhesive is applied.

How Do You Apply Water-Based Bonding Adhesive?

Apply water-based bonding adhesive to the exposed deck using a 9-inch roller with a 1/2-inch nap cover, then apply the same adhesive to the back of the folded-back membrane section. Coat only as much area as you can cover within 5 minutes — the adhesive must stay wet and opaque during the entire window. If it turns clear before the membrane is laid, apply a thin fresh coat to the substrate first.

Roll the membrane back onto the deck immediately while the adhesive is still wet, then use a stiff push broom with nylon bristles to sweep the membrane and force out trapped air. Repeat the process for the remaining half. The application rate is 45 to 60 square feet per gallon for both the substrate and the membrane. Stir the adhesive for about 5 minutes until its color is uniform before you begin.

Perimeter and Vertical Seams with Contact Adhesive

Leave about 6 inches (150mm) around the deck perimeter unbonded during the main application — this zone gets contact adhesive later. Apply a thin coat of contact adhesive to the roof deck perimeter and any vertical upstands, then to the back of the membrane at the perimeter. Let the adhesive dry until touch-dry — tacky with no strings or stickiness — then roll the membrane onto the vertical surface or perimeter. Apply light pressure with a penny roller or push broom to ensure 100% contact.

Critical Rules and Common Mistakes

Never use solvent-based roof cement or aluminum coatings on rubber roofing — both will damage EPDM permanently. Never use water-based bonding adhesive for EPDM-to-EPDM seaming; that requires splice adhesive or seam tape only. Water-based adhesives need temperatures of 4°C (39°F) and rising, with no freezing expected within 48 hours after application. If the existing roof surface (shingles, gravel) cannot be cleaned properly, install a minimum 1/2-inch Polyisocyanurate board fastened to the deck before applying the membrane. And never apply enough broom pressure to wrinkle the membrane — firm sweeping, not heavy pushing.