Steel cassette walls
A new water insulation layer must never be built directly on top of an existing water insulation layer. To provide ventilation, a ventilation space is created between the insulation layers using 6 to 10 mm thick spacers cut out of Finnfoam. The approximately 70 to 100 mm wide Finnfoam spacers are set so that they form a vertical ‘spar frame’ at 600 mm intervals. An additional horizontal run of spacers is set near the floor. If additional horizontal support spacers are required above floor level, vertical ventilation gaps must be left between individual spacers. This is because the ventilation space will be ventilated upwards into the space above the suspended ceiling. To ensure proper ventilation, two or three holes should also be drilled near the bottom of the old wall between each pair of spars.
The tiling of the old steel cassette wall must be cleaned using denatured spirit or a similar cleaning agent. After this, bond the spacer strips to the wall using ARDEX CA 20P or SikaBond T2 adhesive compound. Then install the Tulppa boards by bonding them to the spacer strips again using ARDEX CA 20P or SikaBond T2. The Tulppa boards should also be attached from the profile of the board using the Tulppa Z brackets (and from the bottom board using an O bracket at the bottom edge) aligned with the spacing strips. Self-drilling screws should be used. Joints between boards, through holes and the 3 mm gap between the board and the floor should be sealed following the spar frame mounting instructions.
In all other respects, follow the instructions given for spar frame installation.