Composite decking beams are designed for you to fix composite decking boards over an existing patios or concrete and tarmac areas. Made from strong plastic they are not affected by water. Each beam measures 2900 long x 40 wide x 30 mm high. The beams are screwed down to the ground and the composite boards fixed directly to the beam. The beams are not designed to be used alone as a suspended deck frame. Beams should be laid no more than 350mm apart and double beams should be used wherever to decking boards are to meet on the end known as a butt joint. Please ensure you order sufficient beams to allow for double beams to be used if this is to occur.