How Moisture Can Damage a Deck

While it’s unavoidable, moisture can and will do damage to a deck. It doesn’t happen overnight, but the constant exposure to the elements will take a toll over time. As a puddle sits on a deck board, the water is seeping in. Although the puddle will be dried up in a matter of hours, at least some of the moisture will have found its way into the wood. There are some simple steps that you can take to protect your deck from the elements. Let’s explore the ways that water can harm a deck and the best ways to protect it:

Cracked Deck Boards

Cracked and splitting boards are not necessarily the result of water damage, but they can contribute to it. Water gets into tiny cracks and crevices, expands, and then the wood dries out. This causes it to shrink, and cracks and splits can become even larger. Over time, unprotected wood will warp. When the boards become badly damaged, the only good option is a replacement.

Mold and Mildew Growth

One of the most obvious and visible signs of moisture damage is mold and mildew growth. Damp, dark spots, like under a rug or even underneath a pile of leaves can cause mildew and fungi to feed on the wood. Mold thrives in moist areas, especially those that don’t get much sunlight.

Eventually, moldy areas will become soft and spongy. What starts off looking like an ugly brown or green stain can turn into a mess, attracting insects and causing the wood to break down and decay. It’s important to keep an eye on shady areas, as well as to remove anything that will stay wet or damp for an extended period of time.

Missing Hardware

Another potential issue is missing hardware. Older and untreated wood can crack and split around nails and screws. At some point, they may fall out, leaving a board loose. An older deck may have nails that have worked their way out simply due to age, allowing water to get into that now empty space. Doing a visual check of the hardware should be a part of a regular maintenance plan.

Weakened Ledger Board

The ledger board is what secures the deck to the house. When water collects and settles on and around the ledger board, it can do a lot of damage. The siding and sheathing on the home can become discolored. Depending on the material type, it can grow mildew or rust. Water can begin to enter the home, leading to rot in the framing. Over time, the ledger can become weakened and start to pull away from the house. Eventually, this can lead to a deck collapse, the most dangerous scenario.

Protecting the Deck from Water Damage

Using pressure treated lumber and sealing your deck is the best way to protect the wood from water damage. Re-sealing the deck annually will help lock out moisture, preventing water from soaking into the surface or getting down into cracks and crevices. It helps maintain the deck’s appearance, staving off mold and mildew growth.


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