How to Keep a Deck Board From Cupping

Melissa Lewis

A newly built deck is often an impressive site. However, without proper care, give it a few years and it may become a dingy, gray and warping eyesore. A common type of warping is called "cupping" and is caused when part of the deck board is moist and the wood starts to bend away from the moisture. Fortunately, most homeowners can help prevent cupping without the aid of a professional.

Prevent your deck boards from cupping.

Step 1

Seal all the boards, including the edges, before you install the boards to the joists. Use a sealer appropriate for the deck material and apply it per label directions using paint rollers and paintbrushes. If a builder installed an unsealed deck, seal the deck as soon as possible, getting the sides of the boards as best you can.

Step 2

Reapply topical seals every 3 to 5 years once water no longer beads up on top. Sand the deck first with 80-grit sandpaper, sweep and clean it with a deck cleaner, per manufacturer directions. Then, apply two thin coats of sealer -- as instructed on the label -- with a paint roller and paintbrush for the hard-to-roll areas.

Step 3

Check the water drainage under the deck. The water should not be pooling underneath. Slope the soil a bit so it drains out from under the deck and away from your home. In addition, increase airflow under the decking, if necessary. For example, rather than using solid boards between the deck and ground, use lattice wood boards. The moister the area under your deck, the more likely the wood will cup.