Adhesives & Basecoats

Adhesives and basecoats for render and EWI systems

Adhesives and basecoats are the structural layer of any render or external wall insulation build-up. They rarely get the attention the finish coat receives, yet almost every render failure investigated on site traces back to what sits beneath the surface rather than the surface itself.

Licata manufactures insulation adhesives, reinforced basecoats and adhesive basecoat products formulated to bond to the full range of substrates encountered on UK projects, from masonry and concrete through to render carrier boards on timber and steel frame construction.

What a reinforced basecoat does

The basecoat, with alkali-resistant reinforcing mesh fully embedded within it, performs two jobs at once. It provides impact resistance at the face of the building, protecting the system from the knocks and abrasion an elevation takes at ground level. More importantly, it controls cracking by distributing stress across the whole elevation rather than allowing it to concentrate at weak points.

Every substrate moves. Thermal cycling, drying shrinkage in new blockwork, and differential movement where materials meet all generate stress in the render. Without reinforcement, that stress finds the nearest weak point, which is almost always a window corner, a junction between materials, or a change of plane. With mesh correctly embedded in the centre of the basecoat, the stress spreads and the elevation stays intact.

Mesh position matters as much as its presence. Mesh laid onto the substrate and then covered, rather than embedded within the wet basecoat, does very little. Correct application places it in the body of the coat with adequate cover on both sides and generous overlaps at every joint.

Bonding insulation to the substrate

On an external wall insulation system, boards are adhesive-bonded and mechanically fixed. The adhesive carries the initial bond and distributes load, while the mechanical fixings provide long-term security and resistance to wind uplift. Both are required, and the fixing pattern varies depending on building height, exposure zone and the weight of the finish specified above.

A clay brick slip finish carries considerably more weight than a render or mineral finish, which is why the finish should be selected alongside the system rather than after it. Changing the finish late in a project usually means revisiting the fixing schedule.

Substrate preparation

No adhesive performs on a substrate that is not ready for it. Surfaces need to be sound, clean and free of organic growth, salts and loose material. On refurbishment work, adhesion testing on a representative sample of each property type is strongly recommended before works begin, particularly where the system is being applied over existing render, pebbledash or paint.

• Sound, clean substrate free of contamination and loose material
• Correct primer applied where suction needs regulating
• Adhesive applied at the specified coverage rate and pattern
• Mechanical fixings to the project fixing schedule
• Basecoat applied at the specified thickness with mesh fully embedded

Supply and technical support

Licata adhesives and basecoats are stocked across six branches in Twickenham, Southgate, Dartford, Wickford, Birmingham and Manchester. Our technical team can confirm the correct adhesive and basecoat for your substrate, calculate quantities and advise on application conditions.