Celotex Tempchek FF4000 products should be installed in accordance with these instructions
Ensure that joist spacing is at no more than 600mm centres and that the dimension of the joist is sufficient to span and accept additional loads. If asphalt weathering is to be used, joists should be at no more than 400mm centres.
Install the insulation boards, ensuring that the long edges are parallel to the line of the joists. 50mm x 50mm cross noggings should be inserted between joists to support the short edges of the boards.
Where boards butt together, bed onto twin beads of vapour sealant wide enough to accommodate this arrangement. This completes the vapour control layer (VCL) when combined with each board’s foil facings.
Lay the boards with the plywood side uppermost and stagger board joints. Leave a gap of approximately 2mm between boards and ensure a minimum 20mm bearing on joists and noggings.
Fix Celotex FF4000 with corrosion-proof Suretwist Composite Panel helical fasteners at a frequency to suit the design wind load. Refer to BS 6399-2 Code of Practice for Wind Loads. As a guide, 16 fasteners per board will resist a wind load of 2.22 KN/m2 based on a design load of 0.4 KN per fastener.
Ensure that fixings are no less than 10mm in from the board edge or 50mm from each corner. They should be equally spaced along the supporting joists. Fixings should be long enough to penetrate at least 38mm into the supporting timber.
Stagger opposing fixings where two board edges share the same joist or noggin.
Provide a complete insulation envelope by extending the wall insulation board up to the underside of the roof deck.
Provide a soffit or ceiling below the joists, as the surface of the product is not designed to be used as a decorative internal finish.
Ensure that the plywood is completely dry before any weathering system is applied.
Always use a Type 3G felt to BS 747 as a vapour diffusion first layer when using BUR weathering systems. When using a single-ply membrane, additional 12mm plywood has to be applied on top of the Celotex FF4000.
Temporary protection must be provided for both the insulation and the waterproofing, if significant foot traffic is anticipated either during or after installation.
The structure should be designed so that the finished roof has a continuous, smooth and even slope towards the rainwater outlet or gutter. The minimum fall should be 1:80 to avoid ponding water.
Celotex FF4000 incorporates exterior grade WBP plywood to BS 1203, laminated to the surface. This gives the product excellent strength. Boards can span up to 600mm joist centres to provide a suitable substrate for a variety of weathering systems.
Vapour control layer
Celotex FF4000 has a built-in VCL due to the foil facers but this is discontinuous at the board joints. In some applications no further attention to moisture control may be necessary. Celotex would generally recommend the application of a vapour sealant between the tops of the boards at all edges. This is essential in areas of potentially high humidity.