How to Pressure Wash a Deck Before Staining

Owning a wood deck or patio can be a source of pride, especially when it’s well taken care of and looking immaculate. It can take a lot of work cleaning and applying finishes it. One of the easiest ways to clean a deck and prepare it for staining is to pressure wash it.

Pressure washing a deck before staining requires you to spray pressurized water in a sweeping motion across the entire surface of the deck. Sometimes, if the wood is really dirty or stained, you can use a deck cleaning solution or a chemical stripper with your wash before rinsing everything off.

If you’re interested in getting a better understanding of all the details involved with each of the steps above continue reading on. You’ll get a better grasp of how to properly pressure wash a deck before staining.

Overview

  • Safety Tips
  • Types of Pressure Washer
  • Water Temperature
  • Deck Cleaner
  • Deck Stripper
  • Amount of Pressure
  • Tip Size
  • Technique
  • Sanding
  • Deck Brightener

Being Aware of Your Safety

While the act of pressure washing appears simple enough, there are several things you need to be aware of in order to properly get the job done. One important facet of pressure washing is safety. You consider wearing some protective gear, at least a pair of safety goggles. Long pants and boots will protect your legs and feet from the pressurized water sprays. Keeping the nozzle tip at least a foot away from both the surface of the deck and your feet will help you avoid damage and injury.

Selecting the Right Type of Washer

Pressure washers come in two powered varieties. There are electric pressure washers that are used more commonly used around the house. Gas pressure washers are used for more difficult cleaning work in commercial or industrial settings.

Electric powered washers

An electric pressure washer is sufficient for washing your deck. It’s more affordable and it can be used on other things around the house, such as for washing your car or house siding. These types of washers also require less maintenance than gas washers. 

Gas powered washers

You can use a gas washer to clean a deck, but it really isn’t required. In fact, it actually might be more risky. Because wood is slightly porous in composition, pressurized water can potentially damage it. A gas washer is easily capable of putting out more than 3,000 pounds-force per square inch (PSI). All you really need is somewhere between 1,000 and 2,000 PSI.

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Knowing the Right Water Temperature to Use 

You might think that the temperature of the water isn’t that important. That couldn’t be further from the truth, though. There are actually a lot of differences between the experiences of using each temperature of water. 

Cold Water

The most common pressure washer that you’re going to find is the cold water pressure washer. These are way more affordable than hot water pressure washers and easier to use overall. 

If you are using an electric cold water power washer, this can save you even more money. Because they are not using the added energy of heat, they aren’t going to be take as much electricity which gives you more time to clean without worrying about that energy bill stacking up. 

The best part about cold water power washers is that they can really get the job done but don’t have any of the drawbacks of the hot water pressure washer, like the added risk or cost. This makes this kind of pressure washer the perfect kind for everyday use. 

Hot Water

We all know that hot water is going to clean better than cold water. That is just as true for dishes as it is the deck in your backyard. This heightened cleaning ability can be beneficial when it comes to removing mold or mildew from the surface of your deck. 

When using hot water, you can rest easy knowing that the germs from the mold will be completely eradicated after the wash has been completed. That’s not something you can say after using a cold water pressure washer. 

The downside to using hot water, however, is that it can add more danger to the already ridiculously dangerous task of pressure washing. The water in a hot water pressure washer can get up to almost 320 degrees Fahrenheit. This can add the possibility of burns onto the pile of injuries that you may have already accumulated.

Deciding on a Deck Cleaner

There are a lot of chemicals involved in the process of washing before staining. However, cleaner is arguable the most important step of them all. Whether the deck is clean is going to be will depend on if the stain stays or peels.  

This is especially the case with new decks, which form something called mill glaze. The mill glaze is produced during the process of milling and, if not removed, can prevent any stain from actually seeping into the wood. 

To prevent this, make sure that you’re cleaning your deck thoroughly with the cleaner of your choice. There are a few different types of cleaners for every situation. 

All-purpose

For normal, every-day wear and tear, all-purpose deck cleaners are going to the be your best bet. They are perfect for decks that have been used for a while and have some scars along the way. If all you really need to clean from your deck is a few spill stains or some muddy prints, this is going to be your best option. 

Mildew-focused

The name is pretty self-explanatory. This type of cleaner is used when your deck has had a real mildew or mold problem. These cleaners are stronger than all-purpose cleaners because they are directly fighting against the germs that come from that mildew build up. 

Mildew is identifiable by its light, spotty appearance. It may look like little spots of powder. Mold is usually dark in appearance, usually green or sometimes black. If you find either of these on your deck, you’re going to want to use one of these cleaners ASAP.

Restorative

Weathered decks can look dull and flat, usually taking on a grey appearance. For this kind of deck, you’re going to want to use a restorative or brightening cleaner. 

These cleaners usually require a little more work, needing to be scrubbed in with a brush before rinsing, but they are very effective in making the overall surface of the wood look better.

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Considering a Deck Stripper

If your deck has really pesky stains that just will not come out, a deck stripper is probably necessary. Deck strippers work by chemically removing the previous stain. This is an important step if you are re-staining a deck, or if your new deck has accumulated a very nasty spill or mud stain. 

When an old stain isn’t removed before adding a new stain, the stain is not likely to stay. In fact, it is much more likely to peel and relatively quickly. There are a couple of types of deck stain to look at if you’d like to prevent this from happening. 

Caustic

Caustic strippers are the more common stripper to use. Their process is to break down the previous stain chemically. This erases it entirely, making it easier to continue on. 

Solvent

Solvent strippers are different in that they actually break down the bond between the previous stain and the wood surface, leaving them ready to be removed with a wash. This works a little bit less often than with caustic strippers, but it also depends on the brand and what chemicals are actually being used. 

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Applying the Right Amount of Pressure

When pressure washing anything, the most important thing is knowing what pressure you should be using. Pressure is measured in PSI, or pounds per square inch. 

While some say that the correct amount of pressure to use to wash a deck is near 1500 psi, it is definitely going to be safer to start off around 500 psi. 

If you start lower you can incrementally grow in pressure to find the perfect pressure for your deck. This makes sure that you aren’t going to accidentally damage your deck with too much pressure. 

Possible Damage

There are a million things that can accidentally happen to your deck when pressure washing it. The easiest mistake that people make, however, is using too much pressure. If too much pressure is being used, the water will come out fast enough that it will tear the deck to shreds. 

With soft enough, high pressures can even create holes in the wood. If you are worried about this happening to you, start off at a low psi. You should also be spraying at least a foot to two feet away from the surface of the deck. 

Before beginning the wash, spray one of the steps first to test out your psi level. Starting out on the steps helps because a step board is much easier to replace than any of the actual deck boards.

Choosing the Right Color Nozzle

When it comes to pressure, the force is going to increase when it is pushed through a smaller area. This area (where the water is released from the tip) is called the fan. If the tip size, or the degree that the water is coming out, is small then the pressure is going to be much more than expected. 

Streams of water—like from your kitchen sink faucet or open-face water hose—are around zero degrees. They can get away with this because the PSI put behind the water coming out of them is significantly smaller than even the lowest setting on a pressure washer. 

When pressure washing, you’re going to want to give the nozzle fan a little wider of a space, so that it isn’t so direct. This is going to be around the 50-degree range, but that is more or less. Make sure that it is no smaller than 40 degrees, however.

Using the Correct Technique

The best way to describe the technique needed to pressure wash a deck is a sweeping motion. These motions are easy to after mastering, but they take a little bit of time to perfect. The spray should start at the edge of a board and should move with the grain and along the board. 

This line should be completely straight. If the length of the fan is larger than the boards themselves, bring it down to wear the fan starts at the top of the board and hits some of the board below it. At the end of the board, bring the fan straight down to the end of the next board. Begin sweeping that straight line again, against the grain of this board. 

Keep doing this, slowly and precisely, until all of the boards are completely clean. This may not work out perfectly on the first try and that’s perfectly okay!

Preparing for Staining With Sanding

If you’re re-staining your deck, you’re going to need to sand it down. While stain stripper is going to help chemically remove the stain, there is definitely still going to be some left. Sanding can get the rest of the stain as well as any splinters or rough patches in the wood so that your deck looks even and beautiful.

If you don’t know where to start when it comes to sanding, here are a few options to choose from when considering what to do. 

Sand paper

Sand paper is obviously the easiest and most convenient way to sand your deck. It is a very affordable option, definitely not a massive investment. It is going to take significantly longer than any more professional equipment. 

This isn’t a problem for basic sanding of the deck, but if there really are very tough patches of leftover stain, a more efficient sander might be the way to go. 

Random orbital sander

These sanders are the most expensive choice. They can cover a large surface area and can help make the process go more smoothly than with any other method. Their “random” movements are great for removing any remaining stain. 

They can also make for an easier cleanup. Random orbital sanders use disks, instead of sandpaper, which have little holes on the surface. These holes pick up excess dusk from the area as it is sanding, leaving you less dust to clean later. 

The problem with orbital sanders is that these disks are not as easy to find. Also, while the orbital sander is a powerful tool it may be too powerful for some. This can lead to possible damage to the deck if someone inexperienced is using this sander for the first time. 

Sheet sander

Sheet sanders are basically like the upgraded version of the sand paper method. They vibrate rapidly to sand down the surface much faster than any person could. What makes sheet sanders so convenient to use is that they only need sand paper, which you can get at just about any hardware store. 

There are a few issues with this method as well, though. While sheet sanders can conveniently use sand paper, changing that paper out is much less convenient. Unlike the orbital sander, which takes seconds to replace its disks, switching out the sand paper for a sheet sander can take up a lot of time and effort. 

They are also not incredibly powerful, so they might leave behind some of the remaining stain. This means that you may have to go back over that section with regular sandpaper anyway. Lastly, sheet sanders do not collect dust as they go, so cleanup is more difficult. 

Pole sander

A pole sander is a very, very basic mechanism. If you’ve ever used a Swiffer mop on your floor, you understand how to use a pole sander. It is, essentially, a sheet of sandpaper attached to pole. While this may seem way too simple, its actually very effective without being too complicated.

While sanding with plain sandpaper is fine for smaller jobs, something like a deck is going to take a lot of time. With that time is going to come a lot of muscle pain from kneeling on the ground, hunched over, to sand. If using a pole sander, however, sanding becomes as easy as mopping the floor. 

It’s still going to take much longer than it would be with a power tool, but pole sanders are a great way to keep control of the job without all of the pain of manual sanding. 

Opting for a Deck Brightener

Deck brightener is a product that is going to really help your stain hold. This is an especially crucial step if a caustic cleaner is used on the deck prior. Caustic cleaners, while effective, can end up bringing the pH of the wood up pretty high. 

This ends up lowering the acidity which can make staining your deck much more difficult. Wood, when acidic, becomes much more porous. Those pores soak in the stain which give the illusion of a beautifully colored deck. 

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Final Thoughts

When pressure washing your deck or any surface for the first time, you need to be prepared. This task isn’t exactly easy, but with the proper tools and knowledge it can turn out great. 

Make sure you follow the tips given to ensure that your deck will turn out bright and beautiful, without having to replace any boards. 

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