Installing Hollow Composite Joists on Solid Foundations

Hollow composite joists need a solid concrete foundation to fix to. We advise creating a decline of 1% – 1.5% running away from a property acting as a drainage slope. Drainage holes or gutters can be placed in the concrete foundations if required Measure and cut joists where required.

1. Leave 10mm expansion gaps close to a property and at joist butt joins.

2. Lay joists into position leaving 300mm max intervals between each joist centre to centre.

3. Fix joists into place by drilling holes through the middle groove of each joist and into the foundation. Start at 80mm approx and then at 500mm approx intervals.

4. Double joist where deck boards meet at butt joins allowing 3mm between joists.