The joists, of whatever type, must be installed using specific spacing, not exceeding the maximums detailed below:
- Angle between joists and boards: 90 | 45 | 30
- Maximum centre-to-centre spacing: 40 cm | 20 cm | 10 cm
Silvadec® composite joists use floating installation: simply laid on the ground, they are held in place by the weight of the boards and by the installation clips.
They must not be set or embedded in concrete, or fixed to the ground in more than one place, or fixed to each other, or glued.
When butting, leave a gap of at least 10 mm between joist ends, or, if possible, use an offset rather than end-to-end installation.
You must leave a gap of at least 15 mm between the joist end and a wall or obstacle, to allow for drainage and expansion.
To correct height discrepancies of no more than 5 mm, use only rigid expansion spacers sold specifically for this purpose. They must be inserted at intervals not exceeding 30 cm, under Silvadec® wood composite joists, which are not load-bearing materials.
You are also strongly advised to install the joists in the direction of the gradient of the ground, to encourage water run-off.
Do not install any mesh, felt or geotextile above the joists, so as not to obstruct ventilation or drainage between the deck boards.
We recommend initially installing joists so that they extend beyond the decking edges, and cutting them to length when the decking is complete.
For pedestrian access developments (paths, walkways, etc.), note that deck boards must be placed perpendicular to the walking direction, especially for public areas.
Refer to PU7