Primers

Primers for render and external wall insulation

Primers are the least visible products in a render system and among the most consequential. Their job is to regulate substrate suction and provide the correct key for the coat that follows, and skipping or substituting one is a common cause of uneven curing, patchy colour and premature failure.

Licata supplies substrate primers, bonding agents, consolidants and key coats matched to specific points in the build-up and to the range of substrates encountered on UK projects.

Why substrate suction matters

Every masonry substrate draws water out of the material applied to it. The rate at which it does so varies enormously, not only between materials but across a single elevation depending on exposure, weathering and previous repairs.

Where suction is high and uneven, a basecoat or finish dries at different rates across the wall. That produces variation in colour and texture that only becomes apparent once the elevation is complete, and it compromises the cure of the material, reducing its strength and durability. Aircrete blockwork, old brickwork and previously rendered surfaces are all notorious for it.

A primer evens the substrate out, so the material above it cures consistently across the whole elevation.

Primers before the finish coat

A second primer is normally applied between the basecoat and the finish. This one does a slightly different job: it provides the correct key for the finish, contributes to opacity so the finish colour reads true rather than being influenced by the basecoat beneath, and regulates the suction of the cured basecoat itself.

On coloured finishes in particular, this primer is what prevents patchiness. Applying a finish coat directly onto a basecoat without priming is one of the most frequent causes of colour inconsistency on completed elevations.

Choosing the right primer

Primer selection depends on the substrate below and the product above, and the two together narrow the choice quickly:

• High-suction substrates such as aircrete, old brick and lightweight blockwork need a primer that seals and regulates absorption
• Low-suction or dense substrates such as concrete and dense blockwork need a primer that provides mechanical key rather than sealing
• Existing painted or rendered surfaces need a bonding primer that adheres reliably to the existing coating
• Friable or weak substrates may need a consolidant to stabilise the surface before anything else is applied
• Surfaces to be painted with water-based paints or synthetic coatings need a transparent fixative primer such as Acril Primer to consolidate the surface and even out absorption without altering its colour

Our technical team can confirm the right primer for any substrate and finish combination in a short conversation, which is a great deal cheaper than a variation on site.

Supply across the UK

Licata primers are stocked at all six branches, in Twickenham, Southgate, Dartford, Wickford, Birmingham and Manchester, with trade counter collection and nationwide delivery.