No, you should not use a pressure surface cleaner on a wood deck. Pressure washer surface cleaners have tips that are hard to change out, making it difficult to control the water pressure that emits from the machine. The intense water pressure that emits from a pressure washer surface cleaner can easily damage wood, leaving the deck surface fuzzy and frayed.
While it’s possible to change out the pressure tips in a pressure washer surface cleaner, most household models don’t make it easy. That’s why most professionals prefer, instead, to pressure wash decks with a standard wand with adjustable pressure tips, and chemicals that help to clean wood. Here’s what you need to know to get it done.
What is a Pressure Washer Surface Cleaner?
A pressure washer surface cleaner is a special disc shaped attachment that fits onto the end of a pressure washer wand. They typically have two or more nozzles attached to a bar that spins around within the disc.
The surface cleaner tips generally can provide a more thorough cleaning experience than the wand alone. However, they are better suited to large concrete surfaces such as driveways and patios than they are for wood decks.
The Effects of Using a Pressure Washer Surface Cleaner on a Wood Deck
The high pressure tips on a pressure washer surface cleaner along with it’s rotational cleaning pattern are not ideal for wood surfaces. Not only does the pressure itself do damage to the wood, its working across the grain half the time instead of with the grain. This causes further damage to the wood.
I know, I know. You’ve probably seen videos of people raving about how easy it is to use a pressure washer surface cleaner on a wood deck. But trust me, for every success story out there, there’s 10 stories that end in a deck in bad shape.
I suspect that most people who use a pressure washer surface cleaner on a wood deck “successfully” have a deck that had already been damaged by improper cleaning. So they can’t really see a difference when it’s done.
Or they don’t carefully inspect what the deck looks like up close after it’s dried. And if they do, they don’t post those pictures online.
Most of those time, those photos will reveal damage to the rain of the wood, fuzzy surfaces and burn marks. Especially if a surface pressure washer is used repeatedly over time on the deck.
If you don’t believe me, hop onto a pressure washer forum and see what the professionals say about the dangers of using a pressure washer surface cleaner on a wood deck.
How to Clean a Wood Deck with a Pressure Washer
With proper maintenance, a wood deck can last for many years. Keeping it clean and sealed with a good stain or paint is essential to a deck’s health. Whether it’s for periodical cleaning or to prep a deck for re-finishing, a pressure washer is a great tool to help remove dirt, mold, & mildew that accumulates on your deck.
When cleaning a deck with a pressure washer, it is important to start off with the lowest pressure setting and work your way up in order to avoid causing any damage. Additionally, make sure to keep the tip moving at all times in order to prevent water from pooling and damaging wood surfaces.
Detergent Application
Start off with your detergent application. There are a lot of opinions on what works best for wood, but a lot of professionals use sodium percabonate for the initial application. Mix 1/2 cup of sodium percarbonate per gallon of water to make your detergent solution and apply that solution to the deck with a soap/detergent tip. Let it soak, or “dwell” for 20 minutes.
Brush
Depending on how dirty your deck is, at this point you may need to take a brush to it. If it’s been a decade since the deck has been cleaned and there’s significant mildew accumulation, you may need to take this extra step. Look for a deck brush at your local hardware store. Scrub your deck down thoroughly before rinsing.
Tip Selection
A pressure washer surface cleaner is not ideal to clean a deck because the tips aren’t as easily changeable as they are with a standard pressure washer wand. The general rule is to use a 40° fan tip. If you’re cleaning a hardwood deck, you might be able to drop down to the 15° tip if you encounter some stubborn stains. Don’t ever go below 15° on a wood deck.
You can also lower the PSI on your machine to get to the right pressure. You want to employ a soft washing technique rather than a pressure wash. Soft washing uses low water pressure, high water volume and chemicals to clean.
Are you able to spray your hand 6 inches away from the nozzle without hurting yourself? If so you have about the right pressure. Start off with low pressure and move up if needed. The same advice we give on pressure washing anything, even shoes, airstream trailers, or basement floors.
Wood Varieties Make a Difference
It’s a good idea to determine what kind of wood you’re cleaning before you begin. Most decks are made with redwood, cedar, or pine which are all relatively soft woods. This is why they can be easily damaged by the high PSI a pressure washer surface cleaner emits. Some high end decks are made from Ipe, teak, or mahogany, which are hardwoods. They can withstand a little bit more pressure.
Rinsing Techniques
- Move with the grain, not across it: Intense water pressure can act as a knife. Running a knife across the grain of wood will do far more noticeable damage then running it parallel to the grain. This is why using a pressure washer surface cleaner is not a good idea on a wood deck: you can’t control the direction the tips move in.
- Don’t pause in the middle of a board: You want to go end to end, then take a break. If you have to stop in the middle of a board, try to flick the wand upward to avoid stop lines. If you don’t, those lines will show up after the wood has dried where you broke off suddenly. Not a good look
- Do Not Use a Turbo Nozzle: For the same reasons that a pressure washer surface cleaner is not good for wood, so is a turbo nozzle. Too much pressure with erratic motion that moves across the grain of the wood
- Let the chemicals do the work: Chemical selection and appropriate dwell time (allowing the chemicals to soak) before rinsing is what is going to leave the deck looking like new. Allow the chemicals to clean, not the water pressure.
Final Chemical Application
While the deck is still wet, you want to apply an oxalic acid solution to help brighten it. Mix 1/2 of oxalic acid powder for every gallon of water and apply with your detergent tip. Let that sit for 5 minutes then rinse thoroughly. One precaution to take with oxalic acid: Don’t use it if the deck floats above a natural body of water, as it can be harmful to those living ecosystems.
If it’s impossible to avoid exposing nearby plants to chemical cleaners, spray the plants down thoroughly prior to rinsing the deck. This will help protect the plants from any negative effect.
Using a Pressure Washer Surface Cleaner on an Old Deck
For decks that are especially aged, you may need to use a power washer with an adjustable nozzle that can be set to a lower pressure setting.
You definitely don’t want to use a pressure washer surface cleaner on an old deck, regardless of the type of wood as it could be especially susceptible to damage from the high pressure tips of a pressure washer surface cleaner.
Additionally, be sure to keep the nozzle at least 6 inches away from the surface of the wood and make sure you don’t linger in one spot for too long. Applying too much pressure or spending too much time on one spot can cause further damage to an old deck.
What About Composite Decks?
If your deck is made of composite material such as Trex or Timbertech, you don’t want to use a pressure washer surface cleaner on it. In fact, it may be best to avoid using a pressure washer altogether. These materials are designed to withstand pressure, but using too high of a setting can damage the material or cause fading. If unsure, try looking on the manufacturers website, or contacting them about their warranty policy when it comes to pressure washing vs. soft washing. In many cases the warranty is voided if they company finds out you pressure washed the deck.
