ClassicBond EPDM External Corner Patch

This patch is a pre-cut section of 9" ClassicBond PS uncured Elastoform flashing tape.

In practical terms:

• Manufactured from uncured EPDM membrane
• Laminated to a pressure-sensitive adhesive backing
• Supplied as a 300mm × 225mm (12″ × 9″) patch
• Equivalent to a short length cut from a roll of 9″ uncured flashing tape

It’s designed as a convenient pre-cut solution when you only need to form one or two external corners, without purchasing a full roll of tape.

This uncured EPDM corner patch is ideal for:

• External corners on EPDM roofs
• Upstands up to approx. 150mm
• Corners at:

1. Roof perimeters
2. Parapet walls
3. Skylights
4. Box gutters

• Detailing work where the membrane needs to stretch over a corner without cutting

Because this EPDM is uncured, it can be shaped smoothly around the corner without creating stress points. The EPDM tape begins to cure when it comes into contact with the ClassicBond EPDM primer.

If you have:

• Higher upstands
• Multiple corners
• Longer or irregular detailing

It’s usually more practical to use ClassicBond 9″ PS uncured Elastoform flashing tape, which can be cut to any length required.

👉 Think of this patch as a ready-cut convenience option, while uncured tape is the better choice for larger or repeated details.

1. Clean the membrane surface thoroughly
2. If the membrane is weathered, clean with Weathered Membrane Cleaner
3. Apply ClassicBond EPDM Primer to the membrane and upstand
4. Allow primer to become touch dry
5. Round off all corners of the patch using scissors
6. Position the patch and press it firmly into place, stretching it over the corner
7. Roll immediately with a seam roller and penny roller, working across the edges (not parallel)

⚠️ ClassicBond EPDM Primer is required and is not included with this patch.

Uncured EPDM flashing:

• Has high elongation (can stretch over 400%)
• Is self-curing once installed
• Adapts easily to irregular shapes and profiles

This is why uncured flashing is specified for corners, penetrations at angle changes and complex details in EPDM roofing systems.

External corners are one of the most common failure points on EPDM roofs if the wrong material is used.

Using uncured EPDM flashing, rather than cutting and sticking patches of EPDM like we have seen on many failed roofs - whether as a pre-cut patch like this or from a roll of 9″ tape - is the correct, compliant way to ensure a watertight finish. It stretches, beds in properly, and cures into the detail instead of fighting it. Once installed onto primed EPDM, the flashing tape forms a chemical bond with the EPDM rubber roof, forming a long-lasting corner detail.