External Insulation Guide: Board Adhesive and Plaster Mortar

External thermal insulation (ETICS) is a system application that improves a building's energy efficiency and lowers heating-cooling costs. A successful insulation job depends on combining the right board adhesive mortar, a suitable insulation board and the right plaster mortar. This guide summarises the logic of the system.

Insulation is a system, not a single product

Thermal insulation is a layered system of board adhesive, insulation board (EPS, XPS, mineral wool), anchors, reinforcement mesh, plaster mortar and a finishing coat. If one layer is incompatible, the whole system underperforms, so products must be chosen to work together.

Choosing the board adhesive mortar

The board adhesive is the first layer that fixes the insulation board to the surface. It must provide strong adhesion to both the substrate and the board and resist exterior conditions. A sound, load-bearing, dust-free surface is a precondition for bonding.

Plaster mortar and reinforcement mesh

Once the boards are fixed, reinforcement mesh is embedded and plaster mortar is applied over it. This layer gives the system mechanical strength and crack resistance. The mortar thickness and mesh position are critical for durability.

Application points to watch

• Avoid application in very hot, very cold or rainy weather.
• Lay boards in a staggered pattern; do not align joints at corners.
• Determine anchor count and position by project and wind load.
• Overlap mesh joints and ensure the mesh is fully embedded in the plaster.

How to choose the right products

Facade type, board grade and climate all affect product choice. Review products such as Datex SY113 board adhesive and Datex SS115 plaster mortar to build the system, and get support from the Datex technical team for the final selection.