Plaster connections to windows

ETICS Expert Tip – Part 2

The new requirements made easy

For buildings with and without external thermal insulation composite systems (ETICS), component connections must be carefully planned and implemented depending on their movements, weathering and appearance as well as any other requirements they must meet (e.g. moisture protection, fire protection). Any errors that occur as a result of improper component connections can have serious consequences and permanently compromise a building's functional safety. For this very reason, the German Association for Insulation Systems, Plaster and Mortar (VDPM) has published the leaflet “Formation of details with profiles and joint sealing tapes for external plaster and ETICS”. This leaflet provides information about selection criteria as well as general instructions for the professional planning and execution of connection profiles, including e.g. fabric connection profiles for connections to windows and doors.

Reveal beads with mesh represent the transition between the facade surface and building openings such as windows and doors. At these transitions, different movements of the plaster shell and the window occur due to changes in temperature in the plaster shell and wind stress on the window. In order to enable a permanent, driving rain-tight and crack-free connection between the building components, these movements must be absorbed by the revel beads with mesh without damaging them.
Schlagregendichtheit und hohe Bewegungsaufnahme

Due to high movement absorption, driving rain-tight component connections can be permanently guaranteed (see left picture). The reveal beads with mesh must withstand high three-dimensional movements (see right image).

Choosing the right reveal bead with mesh profile

Depending on the size and installation situation of the window, the movement to be absorbed by the reveal beads with mesh profile used can vary and result in different product requirements. In order to assess the suitability of profiles according to these different requirements, various classifications have been created, with which a testing institute can assess the products in terms of movement absorption and imperviousness to driving rain. The classes range from A to E, with class A representing the highest possible movement and class E the lowest. After testing is complete, the products is given a corresponding classification, which is then shown accordingly by the manufacturer.

To help you select the correct profile for your corresponding installation situation, an easy-to-follow selection table can be found in the VDPM leaflet mentioned above. For connections to windows and doors, the installation situations shown in the following table can occur:
Recommendation for the selection of connections
The profile best suited for the respective application can vary depending on the installation situation of the window, the window size and the existing insulation thickness. First, the planned installation position is selected from the three areas using the table:
  • Window set back in the building wall
  • Window flush with the building wall
  • Window in front of the building wall (in the insulation level)

Once the correct installation position has been determined, the window size is selected from the group in the corresponding column:
  • Small format (up to the largest edge length of 2.6 m or an area up to 2.6 m²)
  • < 6 m²
  • < 10 m²

Finally, only the two groups of insulation thickness are differentiated in the now selected column:
  • ETICS ≤ 160 mm
  • ETICS ≤ 300 mm

The classification required for the profiles used in this case has now been determined.

For example, for a window that is positioned in front of the building wall, is over 6 m² in size and is used in a 140 mm ETIC system, a "class A" profile, i.e. the highest class, should therefore be used.

Special aspects to be considered

In addition to the selection table, there are some important notes that must also be observed:

For example, for coloured metal and plastic windows in ETICS and plastered facades, the use of profiles with high shear strength, i.e. movement absorption capacity of the profile in the longitudinal and transverse axis, (e.g., the higher movement class B instead of class C) is recommended. This requirement is usually already met with class A profiles.

Furthermore, in the case of window or door sizes > 10 m² or insulation material thicknesses > 300 mm, the detailed design must be planned separately by the planner and coordinated with the system holder or plaster or profile manufacturer and the skilled craftsman.

In the above-mentioned leaflet, the VDPM also indicates that, in the case of a connection with an adhesive connection (e.g. EJOT reveal bead with mesh), an adhesive test must generally be carried out.
Adhesive test
If the selection matrix included in the VDPM leaflet, the manufacturer's product classification and the processing recommendations are properly taken into account, the required driving rain resistance will be achieved.

If you need any assistance with the classification of EJOT products or with carrying out the adhesive test, please contact us. Our ETICS service team will be happy to advise you.

Read also the other guides of the ETICS Expert tips and learn more about ETIC systems.