Roof Report

Installation Guideline Tips For EPDM featured image

Installation Guideline Tips For EPDM


EPDM (Ethylene Propylene Diene Monomer) was first introduced in the US Market in 1962 by Carlisle on a section of Chicago’s O’Hare International Airport and in Europe in 1965 by HERTALAN in Kampen (Netherlands). The Middle East oil embargo of the early 1970s drove up the price of asphalt-based roofs and lowered the quality of available asphalt, so the demand for EPDM roof systems skyrocketed. The popularity continued to grow as EPDM became known for its extraordinary hail resistance, weathering resistance, and UV stability.

Since its introduction, continuous enhancements have been made to the components of the system, leading to a way for today’s systems to be more durable, more dependable, and provide greater economic value. Some of the improvements include:

  • Replacing Field Glued Seams with Adhesive Tapes
  • Reinforced Membranes
  • White Membranes for Reflectivity
  • Fleece Backed Membrane for Adhesive or Hot Asphalt Installs
  • Factory Applied Tape to EPDM Sheets
  • Flashing components with Pre-Applied Adhesive Tape
  • Self-Adhering EPDM Sheets

The introduction of membrane splice tapes, which was introduced as an option to liquid applied seaming, is one of the most significant enhancements made in improving the long-lasting performance of the system. It shifted the full dependency of the reliability of contractor workmanship installing the seams, to a more controlled installation environment as well as increased productivity for the contractor.

Below are some guidelines and tips from manufacturers, contractors, and my observations over the years to assure a successful and long performing installation.

Power and Basic Tool Needs

  • Power Source
  • Electrical extension cords
  • Screw gun or drill with Phillips bits (# 2 & # 3)
  • Heavy-duty scissors
  • Measuring tape
  • 2-inch wide steel roller
  • Utility knife and blades
  • Hammer and pliers
  • Screwdrivers (Phillips and Straight)
  • Chalk line
  • Caulking gun
  • 9-inch and 3-inch paint rollers and covers
  • Markers (crayon or pen)
  • Clean rags
  • Scotch-Brite® pads
  • Tin snips and hack saw

Deck Preparation

Properly inspect the decking and make sure it is sound, correctly fastened, clean, and dry in preparation for insulation installation.  If you are adhering or mechanically installing over the deck, you should sweep or machine blow to assure all dust, dirt, or any other objects are removed before install. Any of these objects can affect sheet adhesion and potentially puncture the membrane.

EPDM Sheet Preparation and Adhesive Installation

Lay the membrane on the roof deck (or insulation) and let the membrane relax for about one-half hour. Once the membrane has relaxed, move the membrane into its final position.

Application of Adhesive

  • After letting the sheet relax, fold the membrane in half.
  • Stir the Bonding Adhesive before application and Apply the adhesive starting at the fold and working away from the center.
  • Using a 1/2-inch thick nap roller cover, apply adhesive thick enough to provide a uniform continuous coat to meet the manufactures application coverage specifications.
    • In general, A coverage rate of 45 – 60 ft2 /gal (1.1 – 1.4 m2 /L) may be achieved depending on the substrate. Coverage rates will vary depending on substrate texture and porosity.
  • Once the membrane is laid into the adhesive, broom the membrane with a stiff-bristled nylon push broom.
  • Fold back the remaining half of the sheet and repeat this procedure to install the second half of the membrane.

It is recommended that you periodically check the adhesive application rate to assure proper adhesion of the EPDM to the substrate.

Seam Installation

When laying out the EPDM sheets, allow for a 3-inch wide overlap. Make sure the sheets are lapped so that the membrane to the high side of the roof overlaps the membrane to the lower side of the roof, allowing water to run over the seam and not into the seam.

After folding back the top sheet, prepare each surface of the seam by scrubbing, using a circular motion, with EPDM Seam Tape Primer using either cotton rags or Scotch-Brite pads. Change out rags or pads often to avoid contamination to the seam.

Once the primer has dried, roll the top sheet back over the bottom sheet to allow for proper placement of the guide marks. Place your guide marks using a marking pen or lumber crayon. Marks should be placed on the bottom sheet approximately 1/2 inch away from the edge of the top sheet. This will allow seam tape to be exposed along the completed seam per manufacturers required specifications of 1/8″ to 3/8″.  Never use a chalk line or other type of marking tool that will contaminate the surface of the seam.

After marking the seam, fold back the top sheet. Start to unroll the seam tape a few feet and leave the release paper in place. With the exposed side of the tape facing down, roll out the tape along the length of the seam aligning the outer edge of the release paper with the guide marks. Using your 2-inch wide steel roller, roll the tape with overlapping strokes along the entire length of the seam. If you need to overlap your seam tape to finish the run of the seam, make sure your overlap is at least 1 inch wide.

Fold the top sheet back over the tape. Peel the release paper off the tape at a 45-degree angle, parallel with the roof surface, and allow the top sheet to fall freely onto tape. To remove any air pockets, brush the seam with light hand pressure from the inside outwards. Use your 2-inch wide steel roller and thoroughly roll perpendicular to the width of the tape. Continue throughout the entire length of the seam. Lap Sealant should only be required at the intersections of factory seams, the tape overlaps within the seam, or when two seams intersect each other.

Flashing Details

As they always say, The Devil is in the details. Be sure to carefully follow each manufactures recommendations for installation guidelines on how to flash penetrations, wall, or edge details. While the basics are the same, each manufacture has its specific nuances on how they want the system to be sealed and terminated at these details.

Flashing quality has typically been problematic in our industry and a high contributing source of water penetration into a new install. Laminated components (flashing components that have a pre-applied adhesive tape) have greatly improved flashing quality and should be used whenever possible on any of your EPDM roof installations.

Following these guidelines for hot air welding and referring to the membrane manufacturer’s specification manuals as well as always incorporating internal quality control measures in your installations will give you a quality and long-lasting roof every time.


John Kenney has over 45 years’ experience in the roofing industry. John started his career by working as a roofing apprentice at a family business in the Northeast to operating multiple Top 100 Roofing Contractors. As Chief Operating Officer, John is intimately familiar with all aspects of roofing production, estimating, and operations. During his tenure in the industry, John ran business units associated with delivering great workmanship and unparalleled customer service while ensuring strong net profits for his company prior to joining Cotney Consulting Group. If you would like any further information on this or another subject, you can contact John at