How to Clean, Fix and Maintain Your Wood Deck

Unfortunately, wooden decks won’t last forever. Even though pressure-treated lumber resists insects and decay, it's still vulnerable to precipitation and the sun's rays. This includes other exterior woods like cedar and redwood. To keep your deck looking great, you’ll have to wash it once or twice a year, periodically stain or seal it and you may have to make occasional repairs. Read on to learn how and when to tackle these chores.

Potential Problems to Look For

To make sure your deck is in good shape, once or twice a year examine it from top to bottom. The quicker you find a problem the easier it will be to fix. You may have to move some furniture and flowerpots to inspect your entire deck, but it is worth it. Here’s what to look for.

• Check for rotting or decaying wood.
• Look for loose or damaged boards.
• Inspect the wood where the ledger board meets the side of your house, and where the stairs contact the ground.
• Examine the stability of fasteners, stairs and railings. Wiggle or put weight against the railings to ensure tight connections.
• Look for exposed nails.
• Watch for rusted or corroded hardware like joist hangers.

How To Replace a Damaged Deck Board

If you have a board that's split down the middle or warped, it’s probably best to replace it. Mark the damaged board next to the leading edge of the first support joist that's completely past the split. Be sure not to mark an area that's directly over a joist or you could damage your saw when you begin cutting.

Cut the board using a jigsaw, remove the nails or deck screws and remove the damaged wood. Check the joist for rot or damage while you have access to it. Use deck screws to attach a pressure-treated 2x4 support block to the joist; this support block will hold the replacement board in position. Cut a replacement board to size, pre-drill and fasten it to the support block and joists with deck screws. If you’re replacing the board because it is warped, you may be able to flip it over and use its good side.

You'll want to match the finish stain of the replaced board to the existing boards. Use the same type of stain originally used on the deck. It’s best to pre-stain the replacement board before installing it. If you’re replacing more than one decking board, you may want to restain the entire deck after you’ve made all the repairs. Resealing and staining are key to preventing more damage down the line.

Your replacement board may appear higher and wider than the existing wood, but it should shrink as it loses moisture. If the board is still higher than the surrounding boards after a few weeks, smooth it down with a belt sander. Be sure that all nail or screw heads are recessed into the wood before you begin sanding.

How to Repair Holes, Gaps or Cracks

Holes caused by insects (we’re looking at you carpenter bees) or wood knots falling out or gaps in the wood can be filled with a wood filler or exterior-grade epoxy. Wood filler comes in various colors so you may get a good match to your deck’s color.

How to Fix Protruding Nails

When deck boards expand and contract with the change in weather, nails can come loose. Today, most wood decks are built using galvanized screws, but in years past, nails were more common. To fix the protruding nails, you can simply hammer the nails back into the wood, but know they may come loose again. Or you can pull the nails out and replace them with screws. Make sure to use exterior-grade, galvanized screws, and use screws that are longer than the nails you pulled out. The longer screws won’t come loose because they’ve got more wood to grab onto.

How to Replace Rusted or Corroded Joist Hangers

Joist hangers are made of galvanized steel, so they shouldn’t rot. But if they’re exposed to a corrosive material like melting salts, they can become weak and damaged. To replace a joist hanger, prop up the joist with some 2x4s or another sturdy means for bracing. Remove the old joist hanger using a prybar or a reciprocating saw. The old nails and screws can just be hammered into the wood, they don’t necessarily need to be removed. Slip the new joist hanger in place and, once it’s secure, remove the bracing.

Which Fixes Need a Pro?

Some deck repairs are best left to a professional instead of DIYing the job.

Your deck is spongy underfoot. If the problem is so widespread that it can’t be corrected by replacing a few boards, you’re probably looking at a real safety hazard that requires professional attention.

Your deck is swaying or leaning. This could be a dangerous situation. Even if the problem can be fixed — by installing angle bracing, for example — you need a professional to determine whether repair or replacement is in order.

There are wobbly, loose or rotten posts. If your posts are an isolated problem and the deck is in otherwise good shape, you may be able to repair the posts rather than replace the entire deck, but shoring up the deck properly so it doesn’t collapse while you’re working requires experience. The cause of a loose or rotten post could be because it wasn’t properly installed in the first place, so if you’ve got to replace it, make sure it’s done correctly this time.

The ledger board is rotting. The ledger board is the point where the deck is attached to the house. It’s critical to the stability of the deck. There could be several problems involving the ledger board — bolts rusting through, insufficient bolting and rotten wood. Most homeowners won’t necessarily know what to look for or could have a hard time locating the problem. The deck may need to be dismantled to replace the ledger board, a job better left to a pro.

There are wobbly railings or stairs. If your handrails or steps wobble or lean under pressure, consult a professional even if you think the problem seems easy to fix. It’s a safety issue that must be handled according to building codes.

How Often Should You Clean Your Deck?

The first thing to consider in terms of cleaning wood decks is a schedule. If your deck has heavy exposure to falling leaf debris, pollen or dust, you should probably sweep your deck once a week, and perform a full cleaning twice a year. If your deck stays relatively free of leaves and other debris, you can probably get away with cleaning it once a year. Many people pressure wash twice a year: once in the spring to clean off winter dirt and grime, and again in the fall to remove algae and mold that grew over the summer. You may find it best to wait until late fall to pressure wash so you can remove fallen leaves that have left stains as well as sap or pollen that have built up.

Washing a Deck Without a Pressure Washer

Deck cleaners come in bleach and non-bleach formulas. Bleach cleaners lighten the wood, while non-bleach ones gently remove dirt and grime without damaging the wood fibers or the wood's natural color, they are also friendlier to the environment and not as tough on your surrounding landscape.

When using a deck cleaner, always read the label to make sure you have the correct dilution ratio and how best to use the product. Start by sweeping or blowing away all the leaves and other debris. Gently wash down the deck with a garden hose. Mix up a batch of cleaner. (Again, read the label.) If the wood is extremely dirty, use less water, especially for decks that have been neglected for a long time.

Use a sprayer or a bucket and brush to apply the cleaner. To help the cleaner work better, keep the deck wet while working. Let the cleaner sit on the surface for 15 to 20 minutes. This gives the cleaner time to work on stains and grime. Then give the deck a good rinsing.

Washing a Deck With a Pressure Washer

If you're not sure you want to buy a pressure washer, rent one instead. This way you can learn how to use it and if you do decide to buy one, it'll help you determine what type you need. The key to successful pressure washing is starting slow and working your way up to the appropriate settings.

Like many tools, a pressure washer can be dangerous if used incorrectly. Be sure to start with the lowest nozzle and work your way up to avoid damaging your deck. Wear goggles and closed-toe shoes and keep the kids and pets out of the way.

For cleaning a wooden deck, you'll be best served by using the lowest pressure setting that's still effective. For softwoods like cedar or pine, this is usually about 500 to 600 psi. For harder woods, it can go up to 1200 to 1500 psi.

Choose the right tip to use as well. For wood cleaning, generally, a fan tip or rotating tip (used carefully) will work best. Remember to always start the water pressure in a safe area pointing away from people and glass windows, and start at least 2 feet from the deck, then feather the pressure into a range from about a foot to 18 inches from the deck. Never get closer than 12 inches from the deck unless you're using low pressure.

Start in an area that would be easy to repair or replace, like a stair tread, which would be simpler to replace than an entire deck board. Once you're sure you've got the right pressure setting, keep a consistent distance as you hold your arm steady and sweep, working with the grain of the wood. Also, keep the spray moving. Don't rest in one spot for too long or it could permanently gash the surface. If the washing results in raised softwood fibers, you will need to sand before staining your newly cleaned deck.

Preventing Mold, Mildew + Algae Growth

If you’ve got green patches on your deck, it’s probably because you have standing water or prolonged moisture on your deck that doesn’t run off or evaporate quickly. Remove the green stains with a deck cleaner and a stiff scrub brush or a pressure washer. Here are a few things you can do to prevent this funk from growing on your deck.

• Make sure the gaps between the decking boards are adequate for water to run through.
• Replace warped boards that allow water to pool and eliminate or redirect any sources of excessive water like gutter downspouts and dripping air conditioners.
• Don’t put planters directly on your deck, try to elevate them with stands and planter feet.
• Keep your deck clean, especially when leaves are falling in autumn.
• After removing mold, mildew and algae, apply a fresh coat of stain or sealer.

How to Care for a New Wood Deck

If you’ve just built a deck with pressure-treated flooring, keep in mind there are two grades of this material. The higher-grade has been kiln-dried so it has already shrunk meaning it can be painted or stained immediately after installation. Lower-grade pressure-treated wood (usually has knots) has to acclimate to its space and climate, and you’ll have to wait about six months before you can apply paint or stain. Ask your installer how long you should wait before staining your pressure-treated wood deck.

At the very least, fresh deck construction can benefit from a coat of sealer to enhance and bring out the wood's natural beauty. Sealers come in clear and tinted colors, but none hide the grain of the wood. While this may bring out the wood's beauty, keep in mind that sealers provide minimal UV protection, especially if the sealer is clear. This means your deck is vulnerable to degradation and graying quicker than if you chose a stain or paint. Because sealers offer temporary protection from the elements, you should apply the sealer seasonally. If you prefer less maintenance, a stain or paint is a better choice.