Protect against cupping on decks
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.