Selecting joists

To allow for proper ventilation, boards must never be installed directly on the ground, but on Silvadec® wood composite or aluminium joists , or on durable timber joists (class 4 treated pine or exotic hardwood).

These joists must be at least 42 mm wide, with a below-board height of at least 50 mm.
Silvadec® wood composite joists (50 x 50 mm) are not made of load-bearing materials. They must only be used on flat surfaces and must be in contact with the ground throughout their length (concrete slab or compacted ground with concrete expansion spacers incorporated in the ground).

They must not sit in water. They must not be used directly on weatherproofing (see reference standard). They must only be cut in a way that alters their length, never their width or thickness. For installation on pedestals or piles, we recommend using Silvadec® aluminium joists or solid wood joists (class 4 treated pine or exotic hardwood), installed according to regulations (see reference standard).

For installation on Silvadec® aluminium joists, please refer to document PU26 – Decking accessories.