Adhesive mortar

External thermal insulation adhesive mortar: bonding the insulation and applying the reinforced base coat

One product, two uses on site

The adhesive mortar used in external wall insulation fulfils two successive roles with the same formulation: firstly, it is used to bond the insulation panels to their substrate; then, once the panels are in place, it forms the reinforced base coat which holds and encases the fibreglass mesh before the façade finish is applied. This versatility simplifies the ordering of materials, as a single product covers both stages of the structural work involved in an external wall insulation system. Common formulations are compatible with the main insulation materials on the market – expanded polystyrene, extruded polystyrene and mineral wool – in both new-build and energy-efficient refurbishment projects. The application process always follows the same procedure: mixing the powdered mortar with the recommended amount of water, applying it to a clean, sound and dry substrate, ensuring the working time is observed before setting, then carefully embedding the mesh into the still-fresh layer. Frost, rain and extreme heat should be avoided during application and drying.

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White cement mortar or lightweight lime mortar: which base should you choose?

Traditional adhesion or a more breathable façade: two formulations

This white cement-based formulation offers proven adhesion and good workability, with a light colour that provides the ideal base for the lightest finishing plasters. It is suitable for the majority of external thermal insulation projects, in both new-build and renovation work. The lighter version, made with natural hydraulic lime (NHL 3.5), is designed for façades that need to remain breathable, facilitating the exchange of water vapour through the wall: a particularly important consideration when renovating old buildings or on substrates sensitive to damp. Both mortars are applied in the same way, either by hand or by machine depending on site practice, and are supplied in 25 kg bags. Alongside these adhesive mortars, a versatile polymer-based adhesive sealant completes the range for ancillary bonding and waterproofing work on external thermal insulation (ITE) projects – such as joints, profiles or finishing elements – without affecting the structural bonding of the insulation boards themselves.

How to choose your external insulation?

Steps involved in an EWI installation

Which fixing for which substrate?

External thermal insulation adhesive mortar: bonding the insulation and applying the reinforced base coat

Which mortar for which purpose?

No: the same product is first used to bond the insulation boards, then to create the reinforced base coat that embeds the glass-fibre mesh before the façade finish.

White cement mortar offers standard adhesion and suits most projects. Lightweight natural hydraulic lime mortar favours the breathability of the façade, an advantage in renovation on substrates sensitive to moisture.

These mortars are compatible with expanded polystyrene and extruded polystyrene boards as well as mineral wool, depending on the external insulation system used and the manufacturer's recommendations.