What is Dry Rot and How Can You Prevent Your Deck From Rotting

What is Dry Rot?

Some older decks will develop dry rot symptoms. The symptoms include wood that is spongy, discolored, and may flake and come apart when wet. You can use a screwdriver to detect soft spots in the wood. Even pressure-treated wood is susceptible to rot and decay under certain conditions. On decks, moisture and standing water can cause rot and deterioration. Because dry rot is a fungus, it can spread across a deck like cancer. Dry rot is produced by bacteria that consume the wood's cellulose, leaving it brittle. Additionally, dry rot may attract wood-eating insects such as termites, which will exacerbate the issue.


How Dry Rot Forms

Moisture is the enemy of your deck because it fosters the growth of mildew, mold, and fungus. If your deck has been exposed to excessive levels of condensation or a constant source of water, dry rot may be in its early stages. Under these conditions, it does not take long for wood-eating fungus to penetrate and endanger the deck's safety and structural integrity.


Read more: How to Sand a Wood Deck


To prevent decay, you must minimize – or at least restrict – your deck's exposure to moisture. This can be accomplished with a routine cleaning and inspection regimen. A yearly cleaning will maintain your wood deck's aesthetic appeal, but more importantly, it will help prevent costly repairs, such as rotted decking, by eliminating early indicators of dirt, mildew, and bacteria development. And, having your deck evaluated by a professional every two years will guarantee that you are aware of and able to rectify any moisture source that may develop, before it can cause significant damage to your deck.

Rot-Resistant Woods And Composite Decking

Redwood, mahogany, cypress, and cedar are among the most rot-resistant types of natural wood and can be used to construct a deck that is resistant to decay. However, by its very nature, a wooden deck will always be subject to dampness and rot. You will still need to undertake routine maintenance to keep your deck clean and dry, as well as to ensure its durability.

Alternatively, you may want to try composite decking material, which is more durable, easier to maintain, and requires less time. How? Because composite decking is resistant to decay. Composite decking is created from components that are resistant to moisture and insects, are stronger and more durable than wood, and require minimum maintenance. A composite-constructed deck, for instance, never requires painting or staining. Moreover, the majority of composite decking materials provide a lengthy manufacturer's warranty.

Signs & Causes of Dry Rot on Decks

Untreated wood is subject to decay and rot if exposed to damp, mold, and insect damage over time. The most frequent and severe rot difficulties are caused by a ledger board that has been improperly fitted, allowing moisture to enter the home wall. Because the framing of the house is untreated, it is significantly more susceptible to rot. If your ledger board has rot, it is likely that you will need to replace the entire deck. Additionally, you may need to repair sections of the home's outside wall. If only a few joists or planks have decayed, you may be able to remove and repair only the afflicted sections.

How to Identify Dry Rot on a Deck

Some older decks will develop dry rot symptoms. The symptoms include wood that is spongy, discolored, and may flake and come apart when wet. You can use a screwdriver to detect soft spots in the wood. You can also determine if deck wood is rotted by inspecting for the following indicators of dry rot:

  • These regions are often more susceptible to moisture, so look for soft places around posts that meet the ground.

  • Long sheets of grey mold or wood with a deeper hue are classic symptoms of dry rot.

  • Termites and other wood-eating pests are attracted to dry rot, so if you observe pest damage, it could be a combination of insect damage and dry rot.

  • Inspect the surrounding area for a source or cause of dry rot, including plumbing leaks, gutter failure, sprinkler system issues, and any and all other potential water pooling sources.

  • Not certain if this is dry rot? When unsure, ask an expert to check your deck and provide a repair quote.

Deck Rot Repair

If you notice dry rot on your deck, you must promptly remove and replace the affected boards to prevent further damage. When repairing rotten deck boards, it is essential to thoroughly evaluate the problematic regions. Be sure to investigate all places immediately adjacent to the decaying wood, since even the earliest signs of decay will contaminate your recent repairs. If you are unclear of how to identify or repair rotted spots on your deck, you should contact a professional. Ultimately, your deck is an investment and a valuable asset to the value of your property. It is essential to maintain its health and safety.

How to Prevent Dry Rot on Decks

If your deck has been affected by dry rot, there are measures to prevent it from returning. Find the source of the dry rot first. This could be caused by a plumbing leak, misaligned gutters, uneven boards that lead water to the pool, a malfunctioning sprinkler system, and more. Identifying and fixing the water source problem will be your most important anti-rot strategy moving ahead. In addition, you will need to periodically clean your deck to maintain it clear of grime and mildew, which can promote water retention. Lastly, be careful to protect your wood with a sealant and/or stain to prevent moisture from permeating the wood.

Does Pressure Treated Wood Rot?

Pressure-treated wood does offer protection against decay, but under certain conditions, it can still deteriorate. How? Because pressure-treated wood is not completely waterproof. Without a sealant, pressure-treated wood will absorb and release moisture, causing it to swell and contract, crack, warp and bend, and eventually fall apart. This is why it is essential to clean and coat your pressure-treated wood deck with a water-repellent every year, as well as to inspect your deck on a regular basis, so you can notice any early signs of deterioration before they progress.

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