Eventually, there comes a time when your deck will start to get dirty. Grime, pollen, and even rain will leave a deck with a fine coating of residue that won’t come off easily. It’s easy to just grab a pressure washer and have at it, but it’s more complicated than just squeezing a trigger. So how do you pressure wash a deck properly?
Pressure washing a standard treated wood deck is a two-step process. First, you’ll lightly wash the deck with a cleaning or stripping agent of your choice. Your power washer should be equipped with a detergent tank. Once cleaner or stripper is applied, rinse the deck at a low psi – around 1200 – being sure to get no closer than 6”.
In this article, we’ll also go over how to pressure wash a cedar and composite deck. I’ll give you an in-depth look at the differences between washing the different decking surfaces. As well, I’ll show you step by step how to pressure wash your deck, so you can have your deck looking like new in hours.
- Should I Pressure Wash My Deck?
- Tools and Materials Needed for Pressure Washing a Deck
- How to Pressure Wash a Deck
- How to Pressure Wash a Cedar Deck
- How to Pressure Wash Composite Decking
- Tips and Tricks for Pressure Washing a Deck
- Power Wash Deck Cost
- Pressure Wash Deck Before and After
- When Not to Pressure Wash a Deck
- Pressure Washer Nozzles Chart
Should I Pressure Wash My Deck?
Yes, you should pressure wash your deck. Done properly, a pressure-washed deck is the best way to remove dirt, mildew, and other stains on your deck. It removes stains a cannot, and it does it quickly. Best of all, power washers are simple to use.
- Power washing saves time compared to using a garden hose and scrub brushes.
- Anyone can use a pressure washer as they are extremely simple to operate.
- Cleaning with power washers offers the deepest possible clean compared to other methods to control the power.
- Pressure washers allow you to spread cleaners more quickly.
- Removing deep stains will lengthen the lifespan of your deck.
- Permanent damage to your deck surface is possible if you are not careful.
- Pressure washers can cause nasty wounds and spray debris at high speeds causing serious injury.
- If using deck cleaner, the spray can travel quite far and damage plants and other surfaces.
If you have a cedar deck, power washing is acceptable but only on a very low pressure setting of no higher than 800 psi. Some manufacturers recommend an even lower psi. Cedar is very soft, and higher pressure can permanently damage the wood.
Not all composites are created equal, but for most, you can pressure wash. All capped composites can withstand a light pressure wash. Don’t go too heavy because if you do, you’ll “etch” the wood fiber inner core beneath the cap leaving unsightly marks in your composite decking that you cannot get rid of – ever.
Don’t get composite decking mixed up with PVC decking. PVC is entirely synthetic, but that doesn’t mean you can blast it with water without worrying about damage. It is susceptible to pressure damage, and you shouldn’t go above 1500 psi for PVC decking.
Tools and Materials Needed for Pressure Washing a DeckWhen it comes time to pressure wash your deck, you’ll need a few items beyond just a pressure washer.
Keep in mind that pressure washers are powerful, so the spray will get anything remotely nearby wet. Thus, you’ll have to prepare the entire yard before you wash if you don’t want any part of your home’s exterior to experience damage.
- A pressure washer with a nozzle assortment and detergent tank
- Drop sheets to protect nearby items
- Gloves/eye protection if applying stripper or deck cleaner
- Deck stripper/cleaner and brightener (optional)
- An extension hose is a must, especially if your deck is larger
- A deck cleaning attachment is useful if you have stubborn stains
Having the right pressure washer makes this job much easier. You can rent washers from your local tool rental or Home Depot. Prices will range from $40/hour and up. But if you own a deck, it makes more sense to buy a pressure washer. You’ll earn back your money after you’ve used it only twice, and you’ll save time by not having to go to the rental store every time.
If you opt to buy a pressure washer, know that there are two options: gas and electric. Gas washers are heavier duty, so they are not necessary for a deck. Electric washers are simple, powerful, and easy to use. Get one with a detergent tank so you can add cleaner as you wash. Make sure there is pressure adjustment and that it comes with different nozzles.
How to Pressure Wash a Deck
Pressure washing a deck is all about consistency and movement. Make sure you have a nozzle that can clean the width of a deck board – about 6” – at a minimum of 8” from the surface of the wood. Fan the washer back and forth along the wood grain, being sure never to stop moving as you could damage the wood with a focused blast of water.
1. Remove debris and everything else on the deck. The job of washing your deck is much easier once you have a clean slate – even heavy planters or tables should be moved. Often, the worst stains are hiding beneath furniture and other items sitting on the deck. Moving them allows you to clean the stains before they turn into rot.
Use a narrow tool like a flathead screwdriver or paint scraper to get any gunk out of the cracks between your deck boards, if necessary.
2. Cover plants, siding, and anything else nearby. If you are using a deck cleaner or deck stripper, it is crucial you cover your house siding and landscaping. Chemicals in the detergents could kill delicate plants and stain siding.
Deck strippers, in particular, can be quite unkind to your landscaping if care is not taken to protect the surrounding area. Made up mostly of lye, the deck stripper can stain your siding or cause discolorations.
3. Prepare your pressure washer. Be sure the power washer has a detergent tank. A detergent tank is an attached tank on the washer that allows you to put a deck stripper or cleaner mix into the washer. When you turn the washer on, it will automatically mix water with the detergent in the tank.
Some pressure washers have a detergent hose. In those cases, you simply attach the hose to a bucket of detergent you’ve provided yourself. Then the washer blends the detergent via the hose with the water.
Lastly, be sure to get a pressure washer that has a variety of nozzles. The lower the angle, the greater the intensity of the spray. At a minimum, a 25-degree angle nozzle will do the trick for most applications as it can cover the width of a deck board at about 8”, which is the minimum recommended distance for pressure washing decks.
4. Test the pressure washer on deck stairs. Testing your power washer on a stair is a great place to start for two reasons. One, stairs get lots of foot traffic and will be more worn down than other parts of your deck. They are also a surface most people don’t notice as much as the deck itself. If you damage a stair, it’s likely no one will even know.
If you mess up and gouge the wood, it is much easier to remove a stair tread than to remove a plank from your deck.
As you test your washer, experiment with more and less power and different distances. You want to clean your deck, not kill it. Go easy, then up the intensity of the pressure slightly if you still aren’t seeing results.
5. After testing your pressure washer, apply the deck cleaner. When your deck is dirty, simply removing dirt with water is not a great way to maintain the deck surface. You need to add a deck cleaner to get your deck clean. Deck cleaner typically has a detergent added with bleach.You should read the label on your deck cleaner for further instructions. Some require a wet surface for application, while others do not. Regardless, be sure you wear gloves and long sleeves, and pants when applying so you don’t get any cleaner on you.
If you opt for deck stripper, then you should be careful to follow the directions. Stripper is corrosive, and you don’t want any to sit on your hands or other body parts for any amount of time.
I cannot give a specific method for applying deck cleaner or stripper because all cleaners and strippers have unique application methods. Read the label and follow instructions to the letter. If you don’t, then you risk damaging or ruining the wood.
6. Wash your deck railings first. Starting from the top allows you to work downward. Working downward is essential to prevent streaking from the cleaner or stripper. Therefore, make sure you start with the railings and posts, then do your deck boards after.
Pay careful attention to the psi of the pressure washer. If the product you are using to clean your deck indicates a max psi of 800, for instance, then don’t go above that. Similarly, do not use a higher psi than is allowed for the type of decking and railing you have – see below for guidelines on appropriate pressures for different decking.
7. Keep the pressure washer tip moving. When washing, always keep the nozzle moving and never get closer than 6”. If you can wash effectively at a greater distance, such as 8” or even 12”, then do so. The further away you can stay from the deck surface, the less likely you will damage your wood.
Use a back and forth motion along the grain of the wood, being sure to overlap sections you’ve already cleaned as you go. If possible, try to start each deck board at the start of the board and complete the entire board in one pass. Ending at the end of the board reduces the chance of creating ugly start/stop lines from the power washer.
Finally, pressure washers all come with color-coded nozzles. Green is 25 degrees and you’ll use it to cover the width of your deck board. If that is too narrow to safely clean, use the white 40-degree nozzle and get a bit closer. Never use the red or yellow nozzle on your deck.
The degree refers to the width of the actual spray coming out of the pressure washer. The smaller the number, the narrower and more powerful the spray. Keeping the nozzles wider – white 40-degree nozzle – reduces the chance of damaging your wood. On the other hand, a wider nozzle might not be powerful enough to clean.
8. Rinse the deck lightly. Use a wider nozzle than you did with your cleaning application to rinse the deck thoroughly. This step is merely to remove any residual cleaning products. You will hold the pressure washer further away from the wood at this point.
9. Let the deck dry, then sand, stain, or seal. Never wash your deck without applying some sort of protection afterward unless you prefer the “natural” look of your cedar decking. Or, if you have composite decking, there is no further work required.
But, for standard pressure-treated wood and even cedar, adding a layer of protection will extend the life of the wood and is highly recommended. Be sure the deck is completely dry before you add any type of finish.
How to Pressure Wash a Cedar Deck
The most important difference to know when pressure washing a cedar versus pressure-treated lumber deck is that cedar is less dense than the spruce, pine, or fir lumber that makes up treated lumber. When wood isn’t as dense, it is more prone to dents and dings – especially from a pressure washer.
A quick note – many people confuse the “hardness” of wood with the density. They’re two different things. The hardness of the wood, which uses the Janka scale to determine the hardness, puts cedar harder than any other softwood used for decking, including species used for treated decking.
However, cedar is less dense than the wood used in treated decking. For that reason, it is much more likely to get scuffed than treated wood, even though it is harder. Lower pressure must be used on cedar compared to pressure-treated lumber – nothing higher than 800 psi.
Here are some tips to consider when pressure washing your cedar deck:
- Use a very low psi and keep a further distance away from the wood surface.
- Consider using a deck cleaner, not a deck stripper.
- Use deck brightener after completing to help maintain the original cedar “look”.
- Make sure you stain after drying – otherwise all your work is for nothing.
Failure to stain a cedar deck after cleaning will simply clear out the pores and grain of the wood only to only a fresh new layer of dirt and grime right in. Staining will preserve the cedar look of the deck longer and increase the lifespan of the decking.
How to Pressure Wash Composite Decking
Pressure washing composite decking is straightforward. Nearly all composites are “capped”. This means there is a synthetic layer outside of whatever wood composite core it is wrapped around. That means you are essentially cleaning plastic. Therefore, no fancy deck cleaners or strippers are necessary – a plain dish soap works best.
Let’s take a look at the steps to follow when power washing your composite decking:
1. Remove everything from the deck. Prepare your deck just as you would as if you were prepping to clean a standard wood deck. Covering landscaping is optional as you’ll only be using water with a little soap.
2. Fill the pressure washer detergent tank with liquid dish soap/water mix. Use about one gallon of water to 2 tablespoons of liquid dish soap. Ensure the dish soap is a non-bleach, non-chlorine type that won’t bleach the surface of the composite. Remember, if the composite decking gets a bleach mark, you cannot fix it.
3. Apply soap and water with the washer gently. Use a white tip on the pressure washer and spread the soap and water mix carefully and thoroughly.
4. Scrub problem areas with a gentle brush. Some pressure washers have scrub brush attachments. Make sure the bristles on the brush are soft, not coarse. If you don’t have this attachment, use a separate brush.
You don’t want to risk damaging your composite by trying to get stubborn stains off your composite decking with the pressure washer. Use the washer for general grime, but leave the hard stuff for a brush.
Keep in mind that you can easily “etch” the surface of composites. The wood composite core is very susceptible to damage from the pressure of the nozzle. So the capped outside will remain intact, but the inner core will get grooves from the nozzle. This will cause the surface of the composite boards to have an unsightly appearance.
5. Do a final rinse. Consult the manufacturer’s directions for power washing your composite deck surface. You’ll find that composite products can withstand surprisingly strong pressures – over 3000 psi. However, it is best to be conservative and use lower than the max allowable psi.
6. Rinse the composite surface completely. After rinsing, be sure you remove all soap residue to ensure no streaking or ugly soap marks from soap left standing on the composite surface.
Cleaning Fiberon Composite Decking
Fiberon recommends against the use of a pressure washer for their product. Pressure washer damage is not covered by their warranty, so using such a tool to clean their decking is most definitely at your own risk. However, it can be done effectively if extra care is taken.
For Fiberon composite decking, use a pressure no greater than 2500 psi at a distance no closer than 12” from the deck surface. If mold or mildew is present on the surface, use a brush to manually clean the boards – do not use a pressure washer to remove it.
The last thing you want to do is void the warranty on your Fiberon decking. Use a much lower psi than called for and scrub problem areas manually to avoid any damage.
Cleaning Trex Composite Decking
Trex recommends using a pressure washer as long as you do not go above 3100 psi and get no closer than 8” from the decking surface. In addition to spraying with a pressure washer, they recommend scrubbing surfaces manually where extra dirt and grime have built up.
Even though Trex can withstand higher pressure than Fiberon, it is still best to use a lower pressure setting than the max setting allowed. Start with low pressure and work your way up slowly if you still need more pressure to clean your Trex board.
How to Clean PVC Composite Decking
When you think of PVC decking, which is completely synthetic, you may think that it is ultra-durable. And you would be right – except when it comes to pressure washing. PVC is extremely susceptible to pressure washer damage and you should never use high pressure on this type of decking.
When cleaning PVC decking with a pressure washer, never go above 1500 psi. Stay at least 8” from the surface when cleaning. The PVC is very easily “etched” by high-pressure water, so the further you can stay away with the pressure washer nozzle, the better.
Tips and Tricks for Pressure Washing a Deck
When it comes time to wash your deck with a power washer, there are several things you can do to make the process easier and more effective. From the time of the year to your technique, there are many factors to consider before you pull the trigger, such as:
- Use the proper washer nozzle. Remember that power washer nozzles are color-coded – never use red or yellow. Only use the green, white, and black nozzles.
- Follow manufacturer directions for cleaners and decking. All wood and composite decking manufacturers will have guidelines to follow regarding their products. Consult them before pressure washing. This will give you extra tips to follow, plus information regarding warranties and power washing.
Always make sure your decking product’s warranty allows you to pressure wash. If the warranty is voided by power washing, find another cleaning method!
- Start washing on stairs. If you mess up cheaper to replace a stair than a long deck board. Also, start on the stair that is the least visible.
- Be gentle and start further away from the wood. Use a low-pressure setting to begin, and work your way up to a stronger psi only if necessary.
- Ensure your pressure washer comes with a detergent tank – or hose – and also can adjust the psi.
- Do not pressure wash on a windy day. The wind will blow the cleaner or stripper onto objects and landscaping far beyond your ability to cover them, such as in your neighbor’s yard.
- Also, don’t pressure wash on an exceedingly sunny day. Opt for a cloudy day when UV light is not at its strongest.
Power Wash Deck Cost
Pressure washing is a low-cost job and is a critical home maintenance project you can easily undertake yourself. This is good news for you, the homeowner. Let’s go over the costs associated with pressure washing your deck.
You’ll need some supplies beyond just a pressure washer before undertaking the project. First, tarps or plastic will be needed to cover nearby landscaping and your house siding. Second, you’ll need a deck cleaner or stripper.
Total Cost: $40 or less
Rent a Pressure Washer
Renting a pressure washer is cheap – usually under $40 per day. Like any tool rental, you’ll be required to put down a deposit, which can range from $15-$25 depending on the rental place. You’ll get this back when you return the item.
It’s usually possible to rent for less than a day, but only for slightly less – around $30 per half-day (4 hours). Take it for the full day and use it for other projects around the house after you finish with your deck.
Total Cost: $40 plus tax, not including deposit
Buy a Pressure Washer
Buying a pressure washer is a great idea because an electric model is affordable – under $200 in many instances. Therefore, once you factor in the gas you’ve used to travel back and forth to the rental place, you can justify the cost of buying a pressure washer after only 3 deck cleanings.
Gas pressure washers are more expensive but also more powerful. The cheapest gas pressure washer will be around $300, and they can get way more expensive. However, the cheapest gas washer will be strong enough to clean any deck. Opt for an electric, however, for deck cleaning as you don’t need gas, they’re still powerful enough for a deck, and they are quieter.
Total Cost: $200 for electric, $300 plus tax for a gas pressure washer
Pressure Wash Deck Before and After
Have a look at my deck after pressure washing the right side. As you can see, the difference is tremendous. Note that this is cedar decking, so your deck might look different after washing if you have different decking material.
After I cleaned it, I stained it to make sure that it was protected. While I realize the stain won’t make my cedar look like new forever, it still protects the wood while making it look better at the same time.
When Not to Pressure Wash a Deck
There are instances when you should not pressure wash your deck. Also, if you are remotely uncomfortable washing your deck, then you shouldn’t. Scrubbing it and using a garden hose works too, but it just takes a bit longer. Here are some instances when you should not use a pressure washer on your decking:
- If your deck isn’t too dirty, just rinse and scrub it instead.
- When the deck boards are already damaged, you should replace them instead of cleaning.
- If there is no psi adjustment on your power washer, then you could permanently damage your decking. Avoid washing or get a different pressure washer that has a psi gauge.
- Never pressure wash on a very windy or sunny day. Also, avoid cold days as the detergent or deck stripper you are using may not work effectively.
- Do not use products with chlorine bleach as they could stain your deck permanently.
Pressure Washer Nozzles Chart
Nearly all pressure washers will come with a set of interchangeable nozzles.
They are uniformly color-coded so that there is no mistaking how powerful each nozzle is, regardless of which type of pressure washer you have.
Below is a chart that indicates the degree and color of each pressure washer nozzle.
|Red||0||Stains on very hard surfaces – never use on decking.||Use on concrete or similar surfaces that are extremely hard that you want stripped completely bare.|
|Yellow||15||Use on hard surfaces with very stubborn stains.||Can be used on concrete or hard painted surfaces such as metal.|
|Green||25||For general cleaning of decking, cars, vinyl siding, and other general cleaning applications.||Use on anything from wood to masonry to concrete.|
|White||40||A rinse or cleaning nozzle for softer surfaces such as non-capped composite decking.||Can be used to clean any surface, including painted wood and all types of home siding.|
|Black||Soap||The widest nozzle is excellent for rinsing all surfaces.||Can be used on any surface.|
A good deck cleaning with a pressure washer is basic home maintenance that should occur regularly. At a minimum, you should be pressure washing your deck every several years. This will also allow you to seal your deck regularly and ensure the wood lasts as long as possible.
Finally, make sure you follow your decking manufacturer’s guidelines for pressure washing. Also, follow the directions on the back of the deck cleaner or stripper. The last thing you want is a voided warranty and a damaged deck!