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How To: Adhering EPDM To EPDM

This is article 3 of 3 in our EPDM Series:

EPDM is a cost-effective way to complete a flat roof. EPDM roof systems have been around for over 40 years and are a great choice because they are a lightweight roof that has longevity and few seams. However, the seams and flashing still do need to be adhered to and attached properly to ensure there are no leaks.

how to adhere epdm to epdm3

This step-by-step instruction is for installing an EPDM roof system, however, these same tactics can be applied to adhere to our EPDM slipsheets on our CGW to EPDM roof membranes.

What You Will Need:

  • EPDM
  • Rubber Primer
  • Scissors
  • Splice Tape (typically 3″ or 6″)
  • 6″ Cover Tape
  • Seam Roller

Step 1. Overlap The Two Membranes By A Minimum Of 3 Inches (75 mm)

Step 2. Mark Overlap On The Bottom Sheet

Trace the edge of the top membrane onto the bottom membrane. This will give you an outline for the rubber primer for the EPDM

Step 3. Apply The Rubber Primer To The EPDM Area That Will Be Adhered

Apply the rubber primer in long even strokes using the line marked as a guide. The primer should extend just beyond the top sheet edge. Make sure that the primer is applied evenly and does not puddle.

Step 4. Apply Primer To The Back Side Of The Top Membrane

Step 5. Wait For The Primer To Be Dry To The Touch

Press your finger to the primed membrane. Once the primer is not tacky, you are clear to proceed.

Step 6.  Apply Splice Tape To The Bottom Membrane

Start rolling the splice tape out on the bottom membrane along the primed area. Ensure that the primer is still visible along the edge. Once the splice tape is rolled out the full length of the seam/area, cut the tape and smooth the tape out. If you a rolling up a vertical wall, roll the splice tape up at least 6″. Do not remove the film on the top of the splice tape yet.

NOTE: Splice tape comes in different widths. Make sure that your overlap is consistent with the width of the splice tape. If you purchase 6″ splice tape, make sure your overlap is at least 6″.

Step 7. Cut Splice Tape and Fold In On The Upstand

Cut the splice tape and smooth into the angle change of the upstand making sure that the tape follows the angle change. A 6″ Cover Tape will be installed over the angle change to cover any small gaps between the 2 membranes.

Step 8. Let the Top Membrane fall into place

Step 9. Remove the Splice Tape Film

Remove the film by pulling at an angle and smoothing the top membrane on the tape as the film is pulled off. Be careful to not trap air in the joint.

Step 10. Remove The Film From The Upstand Section

Step 11. Use A Seam Roller On The Splice Joint

Use your seam roller to apply pressure to the new splice joint. Use the seam roller at different angles and directions to ensure that every part of the splice tape has been pressed onto both membranes.

Step 12. Measure And Cut The Upstand Height For A T Patch

Measure the upstand height and add 3″ to your cut T patch. Have a roll or piece of 6″ peel and stick cover tape and cut it to the measurements of the upstand (including the 3″ that you added onto the original measurement). Finish it off by cutting the corners round on the piece of cover tape.

Step 13. Mark The Position Of The Cover Tape And Prime The Area

Place the cover tape in the spot you wish to adhere it to and trace the outline for the primer. Apply the primer evenly like in step 3. 

Step 14. Install The T Patch

Once the primer is dry to the touch the T patch can be installed. Apply pressure with a seam roller.

NOTE: T patches are installed where splice tape intersects with joints or on splice tape angle changes. Cover tape is used in these situations because it has the ability to mold better in angle changes creating a waterproof seal.

Step 15. Install Wall Trim And Lap Sealant (If Necessary)

Install the wall trim if necessary and apply lap sealant above.

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