Simple Deck Maintenance Tips to Protect Wood from Sun and Rain

Factors Leading to Deck Damage and Wood Decay

Most wooden decks are built from pressure-treated lumber. That means the wood undergoes chemical treatments that protect it from bugs and rot. Some use alternative types of wood, such as cedar or redwood, since they contain oils that inhibit mold and decay.

However, even with that protection, wood is still in contact with the elements. Your deck's appearance and structural integrity can suffer if you don't maintain it regularly. 

The damage often occurs for the reasons listed below.

Moisture

Moisture in your wooden decking is the main cause of damage. Rain or melting snow can be absorbed into the wood. The wood then swells when wet and shrinks when it dries. Over time, this cycle creates warping and large cracks.

This moisture problem becomes even more severe in regions with freezing winter temperatures. As water seeps into small cracks in the wood and later freezes, it expands. The expanding ice causes internal breakage and further weakens the wood.

Additionally, persistent moisture promotes rot by creating an ideal environment for decay. When wood remains wet for long periods, several problems can occur, including:

• Mold and mildew. They leave dark stains and make your deck slippery after rain.
• Rot. Fungus breaks down wood, making it weak and fragile.
• Rusted fasteners. Wood screws and nails corrode from moisture. This weakens your deck and puts users at risk.

Biological Growth

The first signs of fungus growth indicate that your wood's protective barrier has failed. This process occurs in two phases: first, the appearance of the deck is affected; second, its structural strength is compromised.

The mold discolors the wood by removing its natural color and turning it gray, black, or green. The fungi then form a thin, slippery film on all board surfaces, stairs, and railings. When moisture from rain or morning dew is present, the deck's surface transitions from dry to extremely slippery.

Rot is the worst deck damage. It happens when fungi grow inside the wood, breaking it down from within. The wood softens and weakens, which can make some boards unstable and even cause collapse, requiring the entire deck to be replaced.

UV Exposure

UV light will break down lignin, which is a natural "cement" in wood that holds wood fibers together. As well as losing its original color due to UV light (losing its rich tones and turning a dull gray), your wood will dry out from the constant sun exposure. This makes it brittle and weak. Due to drying out and the constant sun exposure, it eventually begins to crack at its weakest points, split across the grain, and cause individual boards to warp and bend.

Insect Activity

Wood-eating insects often turn your deck into a home and feeding ground. Termites, Carpenter Bees, and Carpenter Ants pose the greatest threats. They may leave your deck's surface unchanged, but over time, they create internal voids to move through the wood.

Common signs that indicate that unwanted guests exist include:

• Hidden damage is a clear warning sign. Areas infested by termites may feel soft, bouncy, or sound hollow when tapped with a tool like a hammer.
• Look for sawdust-like debris, usually at the deck's base or along beams. This debris signals Carpenter Ant activity.
• Check for visible signs of insects, such as discarded wings, live bees or ants, or faint noises in the wood.
• Sinking wood, deep depressions, or sunken areas signal internal deck damage.

How to Maintain a Wooden Deck - A Homeowner's Checklist

Step 1: Deep Cleaning and Surface Preparation

Clean your deck before restoring or protecting it. Whether it’s routine seasonal maintenance or preparation for painting, this is where you should start.

Here are a few deck cleaning tips for you:

• Clean up debris. Sweep the deck, moving strictly along the wood grain to avoid micro-scratches. Pay special attention to the gaps between the boards, as leaves and twigs can get caught there, trapping water and creating conditions for rot under the boards.
• Rinse. Use a garden hose to wash away all loose dirt, pollen, storm-borne salt, and other debris so aggressive substances stay out of the deck.

For annual maintenance, a regular hose is not enough. You will need a specialized cleaner suitable for your deck type.

• For wooden decks, select a cleaner that penetrates the wood's pores and removes mildew and algae stains. Use a brush to safely clean mold, reducing the risk of damaging softwood fibers.
• For composite decks, use neutral or near-neutral pH cleaners. Avoid bleach or harsh chemicals to prevent permanent discoloration.

If you decide to use a pressure washer, set the pressure to a low level, generally below 1,500 psi, and use a wide spray pattern. Hold the nozzle several inches above the surface and move it consistently to avoid damaging the wood. Otherwise, the wood fibers will become raised and need more sanding.

Step 2: Inspection

When washing the grime from the wood surface, a major point of wood deck care is properly evaluating the deck's overall condition. Wet wood surfaces often show where the protective coating has peeled off most, and cleaning out joints allows you to observe the true state of the fastenings.

What to focus on during inspection:

• Check coating condition. Walk along each board before deck staining. Examine areas beginning to split. If you see splitting, assess severity. Replace boards damaged by rot immediately.
• Railing and stairs strength test. Push down on the railing and inspect each stair. Any wobbling indicates loose connections. Tighten bolts or add supports if the railings move.
• Inspect metal parts. Before sealing, check all exposed nail or screw heads. If you find rusty or protruding fasteners, do not pound them down. Remove old fasteners and replace them with a matching wood screw of the correct size.
• Seal gaps and holes. Fill all chipped holes or empty spaces with exterior wood filler before deck staining. The filler keeps water and bugs out of the board.

Step 3: Deck Repair

Once you've completed the check for areas needing repair, you need to fix them. Repairing minor issues now prevents a "chain reaction" of further damage. A single bad board or a loose screw can put pressure on adjacent components. These types of fixes are usually easy to do yourself.

Replacing Damaged Boards

If there are deep cracks, heavy splits, or the board is bent, replace it before it breaks.

Once you've determined the board needs to be replaced, remove the old board. Pull the nails or screws with a hammer or pry bar, taking care to remove only the damaged section and not harm surrounding boards.

Next, select a replacement board that matches the original's species and measure it for an exact fit.

After preparing the board, drill small pilot holes into it. This prevents splitting when nailing it in place.

If you find that more than 20-30% of the boards require replacement, it's best to replace all upper decking. This area sees the most foot traffic, so a solid upper level ensures a strong walking surface.

Seek professional help from local deck experts through MyHomeQuote.

Tightening Fasteners

To continue, review all joints - particularly those that have the heaviest traffic. Seasonal fluctuations in temperature, along with moisture, will eventually weaken or corrode fasteners. Check all loose screws and verify that the threading on the screw remains intact and has not been stripped.

One method for evaluating whether a screw has come loose from within the wood is to gently strike each one with a hammer. If the screw produces a hollow sound when you hit it, it means the screw has loosened inside the wood. On the other hand, if it rings clearly and with a solid tone when tapped, the screw is securely fastened to the surrounding wood.

DIY Deck Protection from Moisture

Proper sealing is a key step in dealing with moisture. Unlike durable composites, pine and cedar need periodic maintenance with a quality penetrating sealer. Applying sealer provides a barrier against water absorption, preventing rot, mold, and UV damage to wood fibers.

It's equally important to keep the gaps between the individual decking boards clean of debris. If water becomes trapped in the board gaps, you may find yourself repairing water damage.

When performing repairs, select moisture-resistant materials such as composite repair pieces or metal components. These materials, used with adequate drainage, help extend the structure's lifespan and protect the wood deck from rain.

DIY Deck Protection from Sun

Composite materials typically have some level of UV protection. However, natural wood does not. If you don't regularly apply an oil-based finish to your natural wood deck, then it will quickly deteriorate and lose most if not all of its strength.

To prevent damaging the completed deck, begin to protect the railings first and proceed from the top down when applying a protective coating. Use a natural bristle brush for oil-based finishes and a synthetic bristle brush for water-based finishes.

In areas that receive strong sunlight, experts suggest getting the best deck stain for sun protection. For example, both Cabot and Thompson's WaterSeal are well-known brands that can provide significant protection and extend the lifespan of the wood.

Do not apply a deck sealant during peak daytime hours as this may cause the finish to dry prior to being absorbed by the wood, resulting in uneven color and possible discoloration.