Like all construction materials, fermacell Gypsum Fibreboards are also subject to expansion and shrinkage due to the influences of temperature and moisture.
Compliance with the following installation conditions is required for trouble-free dry lining for walls, ceilings and floors: fermacell Gypsum Fibreboards and fermacell panelled (composite) components must not be installed at an average relative humidity ≥ 80%.
For installation reasons, the jointing of fermacell Gypsum Fibreboards must take place at an average relative humidity ≤ 80% and at a room temperature of at least +5 °C. When jointing, the glue temperature should be ≥ +10 °C.
The boards must be conditioned to the surrounding room climate and this must not change significantly in the next 12 hours after jointing. Lower temperatures and relative humidities extend the drying times. fermacell Jointstik should not be exposed to frost during transport and storage.
The filling of fermacell joints must only take place at an average relative humidity of ≤ 70% (this corresponds to a residual board moisture content of ≤ 1.3%). After installation of the walls and ceiling elements, the room temperature should be ≥ + 5 °C.
The same installation conditions apply for the joint filler and finishing work. Wet renders/screeds must be completed and dried before the filling of any joints (joint filler and fine filler), as building moisture impedes the drying of the filler and FST and these can be affected by longitudinal expansion of the boards. Hot/mastic asphalt must be applied before the filling of board joints, as tensions caused by heat can cause cracks in the joints in the lower wall sections.
With the adhesive joint, the hot/mastic asphalt can be applied at a later stage. However, ensure there is sufficient heat distribution and ventilation. Gas burner heating can lead to damage due to the risk of condensation. This applies especially to cold indoor areas with poor ventilation. Rapid heating must be avoided, as this can lead to thermal shock and cracking.