Handling External Corners with QuickSeam FormFlash
 In this installation guide, we will demonstrate how to handle an EPDM external corner detail using Quickseam FormFlash flashing tape. This method of detailing is also ideal to use on skylight upstand corners after the main installation has been completed. Please refer to our other guides for main EPDM installation. What you will need:
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How to Fit an External Corner with Quickseam FormFlash
Step 1
Offer the membrane up to the base of the upstand and fold back enough material to get the 4” roller in and apply the contact adhesive onto the deck, the upstand, and also on the back of the membrane. Note: Bonding adhesive (contact adhesive) is now dark green in colour.
Step 2
Once the contact adhesive becomes tacky, roll the membrane towards the base of the upstand, pushing right into the angle change to eliminate any tenting.
Step 3
Mark a line with the crayon, at 45º from the corner. This will create the resulting “V- shape” on the upstand.
Step 4
Cut down the marked line until you reach the upstand corner. Also cut away any excess membrane, to make handling the material easier.
Step 5
Offer the membrane to the upstand.
Step 6
The rest of the membrane can now be applied onto the roof deck around the corner, and then adhered to the upstand using the same procedure. The corner is to be waterproofed with 2 pieces of Quickseam Formflash, each with a minimum 75mm onto the deck. As with any of the Quickseam tapes, Quickprime Plus needs to be applied to the area the tape is to be mated with. Also ensure the area is clean and dry without any dust or debris.
Step 7
Once the Quickprime Plus is tacky, apply the Quickseam Formflash starting from the top of the upstand working it down towards the base taking care not to let it touch the base just yet.
Step 8
Apply the QuickSeam FormFlash around the corner by 75mm and attach.
Step 9
The Quickseam Formflash can now be mated to the deck area.
Step 10
Using the penny roller, work the Quickseam Formflash right into the angle change, starting from the corner itself. This method will help prevent any unsightly air bubbles from becoming trapped.
Step 11
Repeat the procedure with the second piece of Quickseam Formflash to complete the corner, but remember to apply Quickprime Plus to where the second piece is to be applied.
Step 12
Repeat the procedure to complete the seal using the penny roller, paying attention to the edges and pressing down firmly with even pressure.
The finished detail.
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.