Protect your deck from joist rot

Updated: Nov. 22, 2023

A little diligence and an inexpensive deck flashing tape keep things protected and help prevent deck joist rot.

Grace flashing tape

Last summer, I helped a carpenter buddy tear out a rotten deck. The joists were pressure-treated lumber, so I was surprised at how badly decayed they were. But my friend wasn’t. He sees it all the time: deck joists rotting from the top edge down because the deck boards and debris keep them damp for weeks after rain. So he has two rot-fighting tips for deck owners and builders:

1. Take a few minutes occasionally to pull out the leaves, twigs and other debris that gathers between deck boards, especially where the decking crosses joists. A drywall saw works great for this.

2. If you’re building a new deck, cover the joists with rubbery, adhesive-backed “flashing tape.” This will add $50 or more to the cost of your deck, but that’s cheap insurance to prevent deck joist rot. You can purchase deck flashing tape or other items through our affiliation with Grace Deck Protector 45639 Felt Asphalt Rolls

— Gary Wentz, Senior Editor

Image provided by Grace

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