Timber decking guide - Deck board choice

Deck boards come in a range of sizes from 75mm to 150mm wide and appearances - plain, ribbed or grooved. To enable fast drainage and reduce the effects of movement caused by the moisture content the TDA does not recommend using any board wider than 150mm.

The wood should preferably be straight grained and have a moisture content no greater than 20% to reduce the risk of distortion caused when timber with higher moisture levels dries to suit the local conditions.

No matter what type of deckboard is chosen the edges of each board should have a machine chamfer or radius to aid drainage and prevent damage if boards do move in service.

As a further aid to drainage a slight fall, 1 in 100, should be built into the deck structure. If the deck is attached to a property then the fall should be away from the building.

Grooved boards were designed to facilitate rapid draining of the surface and it therefore makes sense to position such boards with the grooves in the direction of the fall.

A gap of no less than 5mm and no more than 8mm should be left between boards to allow for the natural movement of timber over the seasons and help surface drainage and ventilation of the entire structure. Leave a gap of 5mm where a deckboard abuts a post and no more than 2mm where deckboards abut one another lengthways.

Boards are available with inserts of non-slip material for use in areas where improved grip is required eg steps, ramps and key areas of decks and walkways for public access.

For details of manufacturers of hi-grip boards like those below please contact the TDA