Composite products do not have a wood grain and therefore expand and contract along the linear length of the decking board with minimal expansion across the width of the profile. The clip is manufactured with “wings” to absorb the expansion and contraction across the width of the deck. The longer the length of the board, the greater the potential for change in the length, induced by temperature variances. A critical factor in calculating the correct gapping width is the temperature of the boards when being cut for installation. A hot board lying in the sun will eventually contract after installation therefore opening the gap and a cool board will eventually expand as the temperature of the board increases, closing the gap. All boards should be installed at the same temperature otherwise all the gaps will be inconsistent throughout the deck.
The best guide for ensuring the correct gapping for various lengths being installed across the deck is practical experience in working with the material. For example: a shorter board, around 1m in length does not need a 10mm gap but rather a 1mm gap on joist gaps, as the expansion coefficient of that individual board does not suffice a 10mm gap. If the board is installed in hot conditions, no gap is required and when the board contracts, the gap will be around 1mm, therefore personal intuition and experience is key. Careful calculation of the expansion and contraction of the boards is required for the butt joints. Gapping around rail posts, edges of decks and cladding requires careful consideration as well. Temperatures can significantly increase or decrease the gap width.
Envirodeck is not responsible for any change of joist gaps after installation whatsoever.