Planning of any installation must take into account the dimensional movement that can occur with Formica® Compact Grade laminates, making allowances in the design, fabrication and installation processes. Movement in the length direction of the sheet is about half that in the width direction.
Typical dimensional movement values resulting from extreme changes in relative humidity are:
• Transverse direction of the sheet: 2.5mm - 3.0mm per metre.
• Longitudinal direction of the sheet: 1.0mm - 1.5mm per metre.
General
Compact Grade panels used for wall cladding may be fixed by screwing directly through the face, or by hanging them on a rigid supporting timber or metal framework with ‘Z’ clips. Thinner grades, 4mm - 6mm, may be bonded to a wood-based framework with heavy duty building adhesives.
The chosen method of attachment depends on the installation, board thickness and visual design criteria. In all applications the panels must be fixed to a rigid secure system of horizontal supports at not more than 600mm centres, with vertical support members at the joints appropriate to the detailing. Fixing clips should also be at maximum 600mm centres.
We recommend using panels of less than full board width, both for ease of handling and to reduce dimensional movement.
Do not fix Compact Grade panels to freshly constructed blockwork or brickwork until adequately dry, nor should they be fixed to damp external walls without the protection of a damp-proof membrane. Provide adequate ventilation / air circulation behind the panels either by notching the support members or by packing them off the wall. Typical minimum ventilation access at the top and bottom of the panels should be 20cm2 per square metre of panel area.
Direct Face Fixing
Make through-fixing holes at least 1.5 times the outside diameter of the screw being used, and a minimum of 20mm from the edge of the panel. Use soft plastic bushes to ensure correct centring of the screw in the hole while still allowing for movement. Do not use countersunk screws.
Attaching Fixing Devices
‘Z’ clips and other secret fixing devices may be attached to the back of panels with ‘Taptite’ self-tapping screws or threaded brass expansion inserts. Screws and bolts with slow threads provide better resistance to working loose than those with fast threads. In all cases, first drill a blind pilot hole of the correct size in the back of the panel. The depth of the hole should be at least 1mm greater than the penetrating depth of the screw, and should leave at least 1.5mm of material between the bottom of the hole and the face of the panel.
Rigid items, such as ‘Z’ clips and fixing angles, fixed to Compact Grade panels, should have oversize holes to accommodate differential movement. A slip foil between the two components is also recommended. Do not use expansion fasteners in edge-drilled holes (parallel to the surface).
Edge-to-Edge Jointing
Edge-to-edge joints may be either tongued and grooved, or simply grooved with a loose spline inserted. Whichever method is chosen, the wall thickness of the groove should be greater than the width of the groove. The depth of the groove should be no greater than the thickness of the board, and the length of the tongue / spline should accommodate the maximum anticipated movement. Compact Grade laminates less than 8mm thick are not suitable for edge grooving.
Edge Retaining Profiles
Use edge retaining profiles of steel or aluminium in situations where some movement of adjoining panels is anticipated, such as in vehicle construction.
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