- One option is to cover the deck boards with a watertight membrane. ...
- If you're building a new deck or replacing your deck boards, you can use a system like Trex RainEscape, which installs in the joist spaces before you install the decking.
How do I stop runoff under my deck?
A better way to draw away water and protect the wood in your deck is to install a drainage system under the deck during construction. A quality under-deck drainage system such as Trex RainEscape is installed OVER the joists, so no water comes in contact with the wood that supports your deck.