Gaps of decking boards. What should they be?

What should be the spacing of decking boards when installing a decking? The recommended gaps for installing terrace boards are usually 4-8 mm. The spacing of decking boards depends not only on whether it is installed in summer or winter. Let’s say, we assume that it is dry in summer and the boards are completely dry, so you need to make 7-8 mm gaps if the boards are ~145mm wide, because they will expand when the boards swell in the fall. And vice versa – when installing in autumn, we assume that the boards and relative humidity are high, so a gap of 4 mm is enough, and in summer, when the boards dry out, the gaps will be about 7-8 mm. To work according to this assumption, you can even find special double-sided wedges, one side of which is 4 mm thick, the other side – 8 mm.

What parameters do we need to consider when determining the spacing of decking boards?

Wood type (wood density).
Board diameter (width, thickness).
Wood humidity.
For a year.
It is necessary to take into account the recommendations of the manufacturer or distributor.

Most of the time, we receive requests from customers to install boards leaving 4 mm or 3 mm gaps. Customers argue that larger gaps between terrace boards are ugly and unaesthetic.

MDS terraces recommends following practice and manufacturers’ recommendations, not just aesthetic appearance.

Some practical examples from past seasons

Terraced larch boards 140×28 mm wide, installed with ~6 mm gaps. There were no gaps left in the winter.

Terraced larch boards 140×28 mm wide, installed with ~6 mm gaps. In winter, 2-3 mm gaps remained.

Terraced 120×28 mm wide impregnated pine boards, installed with ~4 mm gaps. In winter, about 2-3 mm gaps remained.

Based on practice and manufacturers’ recommendations, the most optimal gaps for the most popular types of decking boards

For thermal wood boards – 6 mm
For wood composite boards – 4-6 mm
For larch boards – 4-8 mm (if humidity is about 20%, 4-5 mm is recommended)
For impregnated pine boards – 4-6 mm

We recommend always taking into account the listed wood parameters and seasonality. The gaps between the boards are not only necessary for the movement of the wood. This is also important for water drainage and ventilation of the terrace frame.