Installation Guide

Substructure: We recommend 6” x 2” pressure treated softwood available from most DIY or timber merchants (very inexpensive option).
Maximum Joist Spacing (centre to centre): Residential use: Must not exceed 455mm (330mm if at 45° angle).
Airflow requirements: Always allow for adequate ventilation under the deck, use larger gaps and air vents if the deck is to be sunken or enclosed (contact us for more detail).
Board Spacing: Minimum 5mm (increase this to 10mm for hot, humid, damp or poorly ventilated areas).

Butt Joint Gaps: 5mm in-between boards and where a board meets a wall. If area is often hot, humid, damp or poorly ventilated, a 10mm gap to the wall must be left.
Recommended Fixing Method: Only use approved composite deck screws, preferably stainless steel. Screw holes must be countersunk with a SMART-BIT® or 3.5mm combi drill bit (available from UK Composite Decking®). Fit decking over at least 3 joists with 2 screws at every joist point and decking must be screwed down 20-40mm in from the cut end of the board.

Drill & Countersink: UK Composite Decking® can supply a SMART-BIT® that will drill & countersink in one quick operation, designed specifically for composite decking.
Fascia Boards: When attaching fascia boards to the side of a deck, it is important to make sure they are screwed down every 200mm (with 2 screws) along their length.
Using UK Composite Decking® Heavy Duty Posts: If you intend to use the UK Composite Decking® Heavy Duty Post  at any length over 1.4m, then you must use a 2” scaffold pole down the centre to reinforce it (pole must come up to within 500mm of the top of the post).

 UK Composite Decking® Post Caps: These are designed to be a push fit but the legs can be trimmed to suit if necessary.


Lay the boards directly onto a non-self draining surface without consulting with our technical department first.
Use hidden fixings or clips.
Butt boards up end to end closer than the specified amount.