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Primers & Surface Activators

6 products

Primers and activators that make sealants, membranes and adhesives bond properly to the substrate you actually have. Stocked for porous and non-porous surfaces, including specialist grades for green concrete, glazed tile and metal.

Primers & Surface Activators buying guide

Porous versus non-porous

Porous substrates — concrete, screed, render, blockwork, fibre cement — absorb the liquid fraction of a sealant or membrane and starve the bond line. A penetrating primer consolidates the surface and gives the product something solid to grip. Non-porous substrates like glass, anodised or powder-coated aluminium, stainless and PVC have nothing to key into at all; a surface activator chemically modifies the surface so the sealant can bond. Using the wrong one is worse than using none.

Coverage and open time

Primers have a working window. Apply too early and the substrate is not ready; leave it too long and airborne dust contaminates the primed surface, forcing a re-prime. Most sealant primers want the sealant applied between 15 minutes and 8 hours after priming. Membrane primers are typically wider, but still check the sheet — the window shortens in hot weather.

Dilution rates for membrane primers

Water-based membrane primers are usually supplied as a concentrate and diluted according to substrate porosity — a heavier dilution on a dense power-floated slab, a lighter one on an absorbent screed. Getting this wrong in either direction causes problems. Too dilute and suction is not controlled; too concentrated and the primer forms a glossy film that the membrane then bonds to rather than to the substrate, creating a weak layer that can peel cleanly off in sheets.

Testing adhesion before committing

On an unfamiliar or previously coated substrate, the fastest way to avoid a large-scale failure is a small test patch. Prime and coat half a square metre, let it cure fully, then cross-hatch it with a blade and attempt to lift it with tape. Half an hour spent on a test patch is cheap against stripping a whole balcony because the membrane would not bond to an old curing compound nobody knew was there.

Common questions

Do I always need a primer?

Not always, but the technical data sheet decides, not habit. Most manufacturers publish an adhesion table by substrate. Where it says primer required, a failure without one is not covered by warranty.

Can I prime green concrete?

Some primers are formulated for concrete that has not fully cured, but most waterproofing systems require a minimum concrete age — commonly 28 days — before priming. Check the system requirements before committing.

What happens if the primer dries before I coat?

If the maximum open time has passed, the surface must be cleaned and re-primed. Dust settling on tacky primer creates a contaminated bond line that will fail later.