External Wall Insulation

External wall insulation works by adding a weatherproof insulating layer to the outside of your wall. This could be in the form of a protective render. The thickness of the insulation should be between 70 and 100mm thick.

The materials used for external wall insulation are often referred to as a "system" because there are three components that must work together:

  • The insulation material
  • The fixing of framework
  • And the finishing layer, which is weatherproof and aesthetic

The type of system we use is known as Wet render systems. This involves the insulation being directly fixed to the existing wall. It is covered with a render basecoat incorporating a reinforcing mesh, followed by a render topcoat with the desired finish. This can include a polymeric coating that does not require painting.

The External Thermal Insulation Composite System on your house is built up in layers.

  1. Beginning with your outside walls, your Atlas/AVAL approved contractor applies a primer to increase the adhesive properties.
  2. The second layer is an adhesive to bond the polystyrene insulation boards to your walls.
  3. To further ensure adhesion, the insulation boards are also mechanically fixed.
  4. A reinforcing layer consisting of two coats of a cementous polymer around a glass fibre mesh is added for strength and flexibility.
  5. Protective profiles are used on outside corners and movement joints.
  6. A purpose designed over cill provides a new window cill with graphite enhance polystyrene underneath where space permits.
  7. Finally, a topcoat of external render is added for a weather resistant finish.

Optionally, you may have a coat of paint added to the render or wish to have it painted in the future. AVAL acrylic render has excellent resistance to fading, chalking and yellowing and therefore tends to maintain its original appearance over time.

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