Decking Calculator
Find out exactly how many decking boards you need for your new patio deck.
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Frequently Asked Questions
Why do I need a gap between decking boards?
Timber and composite decking boards expand and contract with moisture and temperature changes. A 5mm gap is crucial for drainage, ventilation, and preventing the boards from warping and buckling.
Which way up should grooved decking go?
It is a common myth that the grooves are for grip. In the UK, timber boards are actually designed with the grooves facing DOWNwards to allow air circulation and prevent rot between the board and the joist. However, many people prefer the look of the grooves facing up.
What size joists do I need for decking?
For domestic patios, treated timber joists measuring 100x47mm or 150x47mm (4x2 or 6x2) are standard. They should be spaced no more than 400mm apart to prevent the deck boards bouncing when walked on.
Do I need to treat cut ends of decking?
Yes, absolutely. Any timber that you cut with a saw has its inner, untreated core exposed to moisture. You must brush an end-grain preservative into every cut end to prevent premature rot.