An issue that surfaces occasionally is cupping in decking boards. This is caused by insufficient ventilation under the boards, which means they remain moist for too long. A builder/landscaper can do a lot to prevent this:
- Always place the grooved side of decking boards down. The grooves are there for ventilation and moisture drainage, not to add grip.
- Allow at least 300mm gap between the boards and the ground.
- Provide 2 – 5mm spacing between decking boards.
- Ensure the deck is not built above a frequently moist area e.g. badly drained area, or area prone to pooling. Create a slope in the underlying soil if possible to allow drainage. In some instances it might be necessary to lay agricultural drains.
- Avoid contact with garden mulch.