How to Join EPDM Using 3” Seam Tape
In this installation guide, we will demonstrate how to join two pieces of EPDM together using the 3-inch seam tape. Most domestic EPDM system installations can be completed with the membrane in a single sheet up to 15m x 60m. If you do need to make a seam join, this is a fast and straightforward way to do it. What you will need:
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Joining EPDM Using 3” Seam Tape
Step 1
Ensure the leading edge overlaps the lower sheet by at least 100mm, and has a straight edge along the entire length of the seam.
Step 2
Position and mark the sheet with a white crayon. The line should 18mm from the leading edge of the overlap, all the way down the seam. An 18mm timber batten is a useful tool for this.
Step 3
Flap the leading edge away from the line. It may be necessary to keep it secured with various items so it will not flap back onto your working area.
Step 4
Apply Quickprime Plus with a scrubber pad and handle, from the marked line and at least 100mm wide. Apply Quickprime Plus to the overlapping membrane also. Apply all the way down the seam avoiding puddles by spreading it out evenly.
Notes: Wait for the Quickprime Plus to go tacky. This is especially important, as the tape will not adhere to it if it is in a wet state. Use the “pushed finger” test, and if the finger moves through the Quickprime Plus or is stringy in any way, it is not ready.
Step 5
Once the Quickprime Plus is dry, apply the tape to the primed area. Lay the edge of the roll of tape parallel to the marked line, keeping the tape taut to prevent air bubbles being caught underneath it.
Notes: If the tape veers off at an angle, cut it, peel the backing paper and overlap the tape by at least 50mm. Continue to lay the tape. This ensures you stick to the marked line. This also applies if you run out of tape, and have to start a new roll. Use the silicon roller to ensure the tape has adhered properly to the membrane.
Step 6
Flap the leading edge back, and check the distance to the brown paper edge of the tape. This should be around 18mm. Trim the top leading edge if necessary.
Step 7
Lift up the leading edge, and starting from one end of the tape, peel the backing paper towards you, and let the primed leading edge fall onto the tape, flattening down with your hand whilst peeling.
Step 8
Using a silicon hand roller, roll the entire seam thus eliminating any air pockets.
The finished seam will look like this.
Notes: A T-piece detail is required whenever the end of a seam needs to join an adjacent membrane as shown below. An excess of membrane from underneath the original seam will need to be cut back at a 45º angle. If this is not done, it will leave an unsealed entrance point for water ingress.
Step 9
Cut away the excess membrane as shown.
Step 10
Do the seam join as usual and use the rollers to firmly press down the seam.
Step 11
This area now needs to be reinforced with a patch of Quickseam Formflash, of size 150mm x 225mm. This covers the necessary 75mm from the weak points. Mark the area to be primed.
Step 12
Apply Quickprime Plus using the pad, exceeding just beyond the crayon lines.
Step 13
Apply the Quickseam Formflash, and use the rollers as normal.
The finished T-piece should look like this.
More guides from PermaRoof UK
PermaRoof UK offers support to both trade and DIY for EPDM application. We provide a further range of installation guides, datasheets, product and technical information in the Knowledge Base and in our corporate resource library here.
Become an expert with our EPDM training days
We run accredited EPDM training days for both sheet membrane application and liquid waterproofing. Training days are held at the PermaGroup headquarters in Derby at our purpose-built, approved training centre. Intensive, one-day courses and certification.