Does flashing tape need a primer?

It's one of the questions we get asked most. The short answer: on a clean, dry, sound surface, Supraseal® doesn't need a primer. Preparation matters far more than primer. Most tape failures we see come from tape put on dirt, dust, damp or old sealant, not from a missing primer.

Why butyl tape usually doesn't need priming

Butyl adhesive is soft and tacky, and it flows into the texture of the surface when it's rolled. On smooth, non-porous materials like metal, glass, GRP, plastic-coated steel, uPVC and single-ply membranes, there's nothing for a primer to do. The tape bonds directly, and the bond strengthens over time.

The test: is your surface ready?

Before you tape anything, check four things:

1. Clean. No dirt, moss, algae, oil or grease. Scrub it, rinse it, and let it dry.
2. Dry. No rain, dew or frost. Run your hand over it. If it feels cold and damp, wait.
3. Sound. Nothing loose or flaking. Tape sticks to whatever it's put on, so if that surface comes away, so does the tape.
4. Dust free. Rub a finger over it. If it comes away dusty or chalky, the surface needs more work.

If your surface passes all four, tape it. No primer needed.

When a primer helps

Some surfaces fail the dust test however much you clean them. These are where a compatible tape primer is worth using:

• Old, crumbly brick and render that keeps shedding dust.
• Porous concrete, blockwork and mortar joints that soak up moisture and hold dust in their surface.
• Weathered fibre cement with a chalky surface.

On these, a primer seals and stabilises the surface so the tape bonds to something solid. Brush off as much loose material as you can first, apply the primer as its manufacturer directs, and let it go tacky before taping.

What about old sealant, felt and coatings?

Tape bonds to the top layer, so that layer needs to be stuck down well itself.

• Old sealant and mastic: remove as much as you can. Tape over old, hardened sealant only bonds as well as the sealant does, and silicone sealant won't let anything stick to it.
• Felt roofs: sweep off loose granules and tape onto sound felt. Our felt roof guide covers this in detail.
• Painted surfaces: tape onto paint that's firmly stuck. If it's flaking, scrape it back.
• Aged EPDM: clean off the chalky surface with a membrane cleaner first. See how to repair an EPDM roof with tape.

Get the most from the bond

• Overlap the defect by at least 50mm on every side.
• Round off the corners of patches.
• Roll it firmly, especially at the edges, with a seam roller.
• In cold weather, warm the roll before you use it. More on that in our guide to applying tape in cold or wet weather.

Supraseal® Weatherproofing Tape bonds to EPDM, TPO and aged PVC single ply, SBS bitumen, concrete, masonry, fibre cement, tiles, slate, lead, aluminium, copper, glass, timber and fibreglass. It's UV stable, bitumen free and backed by a 10-year warranty.

Not sure about your surface? Email hello@supraseal.com with a photo and we'll tell you.