How much decking do I need?
Divide your deck's width by the effective board width (including the gap between boards) to get the number of board rows, then multiply by the deck's length for the total board length to buy. Joists run underneath, perpendicular to the boards, spaced at regular centres — 400mm is the standard, slightly more conservative choice.
Boards typically run the length of the deck — divide the deck width by the board’s coverage width (including the gap) to work out how many rows you need.
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