Pressure treated wood is still a popular choice for decking and other outdoor fixtures. But even though it is more durable than non-treated wood, it is still susceptible to problems like mold, mildew, and moss. In order to keep it in good condition, you must clean it properly. In this article, I will tell you everything you need to know about cleaning pressure treated wood.
What Causes Pressure Treated Wood to Need Cleaning?
Pressure treated wood is a suitable material for use outside because it is durable, but it still requires cleaning sometimes. There are several reasons why pressure treated wood may need cleaning. A buildup of water on the wood that has not been able to dry will cause mildew and mold on your deck. If you have a pool, chlorinated water will get on the deck and can potentially cause damage if left for too long. If the wood is in an area that doesn’t get much sun, water will not dry out and this increases the chances of mold and mildew.
You may also notice a buildup of dirt on the boards, as a result of a too-wet environment or from bird droppings. General foot traffic will bring dirt and soil from around the yard onto the deck as well.
Failing to clean pressure treated wood properly will considerably reduce its lifespan and once mold and mildew have set in, they can be difficult to deal with. But with some regular cleaning and a few preventative measures, you can keep pressure treated wood in excellent condition.
RELATED: How Long Does Pressure Treated Wood Last?
How to Clean Pressure Treated Wood?
There are lots of ways that you can clean and protect pressure treated wood.
1. Bleach
There are many products on the market that will clean and deodorize pressure treated wood, such as bleach.
Combining a cup of chlorine bleach with about 5 gallons of water in a spray bottle and then spraying this mixture onto your deck can help to kill any mold or mildew. Avoid getting the bleach mixture on metal objects such as nails, screws, and railings.
It is also important to note that excessive bleach use can stain the wood and strip some of the color. So, always ensure that you dilute the bleach properly and you don’t use it too often.
2. Sanding
If mold and mildew are already present on the wood, you can sand it off. Using fairly coarse sandpaper (60 to 80 grit) allows you to strip away dirt and stains on the surface. Afterward, clean the deck thoroughly with soap and water.
Bear in mind that sanding pressure treated wood can remove the protective coating that is applied during the treatment process, leaving the wood more exposed to mold and mildew in the future. So, once you have sanded it and you are happy with the surface, you need to finish the wood with a protective coating.
Sanding is an excellent way to deal with dirt and stains, but if you have a severe mold problem, it may not be as effective. You are taking off the top layer but not killing the mold spores that are set deeper into the wood.
3. Pressure Washing
Pressure washing is a common way to remove mold, mildew, and dirt from pressure treated wood. A pressure washer will blast away anything on the surface, leaving the wood nice and clean. However, it is important to get the pressure right so you don’t damage the wood. 1000 to 1200 psi is ideal for cleaning wood. Anything higher and you risk damaging the wood.
When pressure washing, you can use plain water or you can opt for a pressure washer with a chemical intake and use specific wood cleaning products. If you want to refinish the deck after cleaning, you can add stripper to the pressure washer to remove the old protective layer.
But if the surface of the decking simply needs cleaning, you can use water to remove dirt without damaging the finish of the wood.
4. Scrubbing with Water and Soap
Soap and water do a great job of cleaning pressure treated wood. It is also a simple, cheap method that anyone can do at home.
Mix some dish soap with water in a bucket and then you can use an old mop or broom to scrub the decking. You shouldn’t need to scrub hard or for very long periods of time. If you have stubborn stains or mold, you can use a stiff bristled brush to scrub the dirt off.
Always make sure to use ammonia-free soap because ammonia can damage the wood. Usually, a simple washing up liquid diluted with water will work perfectly.
5. Vinegar
Mixing water with vinegar will also clean your deck. You can combine 1 part white vinegar to 8 parts water, fill a spray bottle with the solution, and then spray it onto the wood in order to kill any mold or mildew. Avoid using this mixture on areas where you have
6. Wood/Deck Cleaning Products
Deck cleaning products can be effective, but only when used in the right situation. It’s important to remember that they will strip the wood stain from your deck, so they should only be used when you want to refinish the wood. Otherwise, you can use soap and water, bleach solutions, pressures washers, vinegar, etc.
If you do want to stain your deck and you need to clean it first, there are two types of wood cleaning products to choose from; bleach-based and oxygenated. In the past, bleach cleaners dominated the market, but they have since been taken over by oxygenated cleaners. In high concentrations, bleach can damage the wood, especially if you are using bleach cleaners every year. Oxygenated cleaners, on the other hand, will not damage the wood and they’re safer for use in the garden.
7. Applying Wood Stain
Applying wood stain is crucial for protecting the wood and giving it a nice finish. Ideally, you should do this every 1-2 years, depending on the state of the deck.
Before staining, you need to strip the old finish. You can do this using a wood cleaning product or a pressure washer with chemical intake. When the old stain is fully removed, make sure you leave plenty of time for the wood to dry out. If you don’t, the stain locks moisture in the wood and that’s when mold and mildew start to grow.
Check out our 10 Best Stains for Pressure Treated Wood in 2022
Always read the guidelines about the application because every product varies. Failing to apply it according to the guidelines can affect drying and curing times, and ruin the finish. But as long as you do it properly, applying wood stain will increase the longevity of pressure treated wood.
8. Deck Brightener
If your decking has lost its color, there are deck brighteners that can restore it. These usually come as a detergent solution which you dilute with water and then spray onto the wood. It works by altering the pH of the wood to make it more acidic, which neutralizes the effect caused by cleaning products. The pores of the wood open up and accentuate the natural grain, restoring it to its former glory.
You can use a deck brightener after cleaning to give you a natural finish. It also prepares the wood for finishing because the open pores soak up the stain much better. If your deck is particularly old, consider stripping it back with a deck cleaner, then applying a brightener before staining it again and it will look brand new.
9. Coat with Paint
Painting pressure treated wood is an excellent way to give it a layer of protection and cover up big stains. Sometimes, the wood is too far gone to bring it back to life. But if you clean it properly to kill mold and mildew, you can give it a new lease of life with a coat of paint.
It’s best to use water-based latex primers and compatible paint on pressure treated wood. Avoid using oil-based paint and always make sure you are using a specific exterior paint.
How to Prevent Pressure Treated Wood from Mold, Moss, and Mildew?
Cleaning pressure treated wood is important, but you also need to focus on prevention if you want to keep it in good condition.
1. Providing Shelter
Mold and mildew grow because of excess moisture, so protecting the deck from the rain is a big help. Building a canopy over the deck will prevent rainwater from building up, and it also protects against sun bleaching too.
2. Sealing the Wood
Sealing the wood creates a water-resistant barrier to protect it. You can also find products that offer UV protection too, and a sealant will bring out the natural look of the grain. You can find some great information about the best clear coats for outdoor wood in our article here.
Using wood sealer whenever you refinish your deck will give you superior protection.
3. Regular Cleaning
Things like soil or fallen leaves sit on wood and create more moisture. If left, this leads to moss, mold, and mildew growth. That’s why regular cleaning is so important. As discussed previously, there are a lot of different methods for cleaning your deck, but even a quick sweep and rinse with a hose will help.
How to Clean a Deck with Deck Cleaner?
Follow these steps when using a deck cleaner for the best results.
1. Clear the deck – remove any furniture and use a broom to sweep away and loose dirt and debris.
2. Mix the cleaner/cleaner concentrate with water (if necessary) – check the directions on your specific product to see how much water to add.
3. Apply the cleaner – use a pump sprayer or half-gallon garden sprayer for best results. However, you can also use a mop and bucket if you prefer. Either way, make sure that you get good coverage and you work the cleaner into the wood properly. You may also want to use a stiff brush to deal with any stubborn spots.
4. Rinse the wood – after a few minutes, rinse with a hose or pressure washer to remove any excess dirt and debris.
5. Allow it to dry – wipe away any puddles or other moist areas after you have finished rinsing. If applying stain or sealer, ensure that the wood is fully dry beforehand.
Related Questions
Can I Use a Paint Sprayer to Apply Deck Stain?
Yes, you can use a paint sprayer to apply deck stain. In fact, it’s a good way to save time and get good coverage, but it can go wrong if you don’t know what you are doing. You should practice with the sprayer first on a hidden part of the deck, and wear protective clothing too.
Will Bleach Damage Pressure Treated Wood?
Bleach can be effective when diluted properly. However, if used too often or in high concentrations, it can damage the wood. So, be careful with bleach-based cleaners and look for alternatives where possible. Vinegar is a safer homemade deck cleaning solution than bleach.
Can Pressure Treated Wood Rot?
Pressure treated wood is given a layer of protection so it is more resistant to rot. But that doesn’t mean that it won’t rot at all. If you don’t look after it properly, it is prone to mold and mildew. That’s why a regular cleaning schedule is so important.
What’s the Difference Between Pressure-Treated and Non-Treated Wood?
Pressure treated wood is treated with chemicals to make it more durable. It can resist the effects of termites, fungi, and insects that would otherwise cause serious damage. Non-treated wood doesn’t have this layer of protection, so will not last as long.
Non-pressure treated wood is generally cheaper, but it doesn’t have the same resiliency as pressure-treated lumber. That means that non-treated wood can warp or crack easily, and it’s also more susceptible to rot too. So, you get what you pay for in this case. You can treat untreated wood yourself, but it is unlikely to be as weather proof as pressure treated lumber.
Final Thoughts
Cleaning pressure treated wood is important if you want to extend its lifespan and keep it looking nice. Overall, I would recommend steering clear of bleach-based cleaners. Oxygenated cleaners are just as effective and do not risk damaging the wood as much.
These cleaners should be used annually, before staining and sealing the deck. In the meantime, keep up with a regular routine of cleaning with soap and water or vinegar solutions. These will remove any dirt and debris without damaging the wood or removing the protective layer from the stain and sealant. If your deck is particularly damaged, you can use a brightener to bring it back to life before staining.
Follow these simple steps and your pressure treated decking will stay in perfect condition for years to come!
Jamie is the founder of The Backyard Pros. When he was 15 years old he started working at a garden centre helping people buy plants, gardening products, and lawn care products. He has real estate experience and he is a home owner. Jamie loves backyard projects, refinishing furniture, and enjoys sharing his knowledge online.