How to Install EPDM on a Flat Roof

Written by larry simmons
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How to Install EPDM on a Flat Roof
Prevent your roof from leaking with the installation of an EPDM membrane. (Jupiterimages/ Images)

Using EPDM as a roofing membrane on a flat roof is a common technique for adding a waterproof layer to the roof. EPDM is quick to install, cutting to a fraction the time spent in laying the rubber membrane in comparison to the time and labour requirements of other roofing materials such as tile or shingles. Installation consists primarily of cutting the EPDM sheeting to fit and then gluing it in place with a seal applied to any seams when utilising multiple sheets. With a few finishing touches following the gluing, the EPDM is ready for service, keeping your flat roof leak free for as long as the material remains undamaged.

Skill level:

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Things you need

  • Stiff bristled push broom
  • Mild liquid detergent
  • EPDM membrane
  • Utility knife
  • EPDM adhesive
  • Medium-nap paint roller
  • Chalk
  • Seam primer
  • Seam tape
  • Seam roller
  • Caulking
  • Termination bar
  • Screws
  • Screwdriver

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  1. 1

    Prepare the roof for EPDM installation. Clean the roof thoroughly by sweeping it with a stiff-bristled broom then washing the surface with a mild liquid detergent. Rinse the roof off with clean water after washing and wait for it to dry.

  2. 2

    Check the rooftop for any loose materials that can shift beneath the rubber. Fasten down the loose surfaces following the recommendations of the surface material manufacturer. Remove any sharp objects that could cut through the rubber membrane as well.

  3. 3

    Unfold the EPDM over the roof's surface. Place the EPDM so that it overhangs the edges of the roof by 3-inches and runs up the sides of any structures on the roof 12-inches. Wait 30 minutes for the rubber to adjust in place. Overlap adjoining pieces of EPDM 3-inches. Cut the membrane to fit where necessary using a utility knife.

  4. 4

    Fold the EPDM in half to reveal part of the roof for adhesive placement. Stir the EPDM adhesive with a wooden stir stick, then apply the adhesive to both the roof and the exposed rear of the EPDM membrane. Use a medium-nap paint roller to spread the adhesive in place, working in slightly overlapping rows along the length of the two surfaces. Avoid applying any adhesive to the overlapping portions of any EPDM membranes. Wait for the adhesive to dry to a tacky state, where it's slightly sticky to the touch but no longer wet looking.

  5. 5

    Unfold the EPDM back onto the roof, taking care not to introduce wrinkles into the material. Go over the EPDM with the push broom to ensure that the entire membrane touches the roof and to push any air bubbles out from beneath the rubber. Repeat the adhesive application process to the other half of the membrane as well as to any other EPDM panels on the roof.

  6. 6

    Locate all overlapping seams. Mark a line on the bottom membrane with chalk one inch farther than the overlapping membrane reaches, parallel to the overlapping line. Pull back the overlapping membrane and brush a layer of seam primer to both the bottom of the overlapping piece and to the top of the membrane that you're overlapping, from the edge of the overlapped membrane beneath the top membrane to the chalk line. Wait for the primer to dry completely, about 30 minutes to an hour.

  7. 7

    Lay a piece of seam tape onto the bottom membrane running from the chalk outline to the edge beneath the top membrane. Leave the paper backing sheet in place. Roll the tape down securely with a seam roller then fold the top EPDM sheet back over the lower one.

  8. 8

    Remove the paper backing from the seam tape and press the top EPDM membrane onto the tape to seal it in place. Use the seam roller over the membranes to set them tightly together.

  9. 9

    Run a bead of caulking along the edge of the membrane where it meets any walls or structures. Set a termination bar along these edges and screw the bar in place against the wall. Cut the membrane above the bar with a utility knife. The termination bar will keep the membrane from pulling free, while the caulk will keep water from seeping beneath the edge of the EPDM. Run a second bead of caulking along the top of the termination bar against the wall.

  10. 10

    Use the adhesive to glue the edges of the EPDM to the edges of the roof. Caulk and terminate the roof edges as you did the wall and structural edges, cutting the excess EPDM from the roof edge overhang.

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