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How to Pressure Wash Wood

A pressure washer can quickly become a valuable tool for washing a range of hard outdoor surfaces in short amounts of time, including the hardwood on decks and patios! 

How do you pressure wash wood? With the right tools and supplies, pressure washing hardwood surfaces is relatively simple. Soak up the surface using a 65 degree nozzle. Then wash and rinse using a 40 degree nozzle. Lastly, apply a layer of wood treatment. That’s it!

Overview of Steps

  1. Gather supplies.
  2. Inspect the wood surface.
  3. Sweep the area.
  4. Pretreatment.
  5. Prepare the pressure washer.
  6. Wash.
  7. Rinse.
  8. Apply a layer of wood treatment. 

Instructions

Step 1: Gather your supplies

One of the most important things you’ll need before you start pressure washing is protective gear! Although you’re dealing with soap and water, pressure washers can be quite dangerous if mishandled. Make sure you wear long clothing, slip-resistant shoes, gloves, and goggles before starting.

Along with safety gear, you’ll also need the following supplies; some of which will only be necessary if you plan on treating the wood surface after cleaning:

  • Bristled push broom
  • Pressure washer
  • Pressure washer nozzles (fan or rotating tip; 20, 40, and 60-degree nozzles; soap nozzle; scrub brush attachment) 
  • Cleaning solution or deck cleaner
  • Stiff scrub brush (synthetic bristles, ideally)
  • Sandpaper (80-grit)
  • Plastic drop sheets (to cover immovable plants)
  • Paint roller with an extender
  • Paint tray
  • Natural bristle paintbrush

Step 2: Inspect the wood

Make sure you thoroughly inspect your wooden surface before beginning any work on it. Check for signs of termites, rotting, or anything else that may suggest that parts of your patio or deck may need replacement or treatment first. If all looks good, then it is safe to move on to the next step!

Step 3: Sweep the area clean

Make sure you remove all furniture, plants, or other objects from the hardwood surface first. Once the area has been cleared, use your bristled push broom to sweep away any loose debris (leaves, small branches, dust, etc.) on the surface. Doing this will help you identify any tough stains—such as mildew, grease, or tree sap—left behind. 

Step 4: Pretreatment 

This would be the time to treat any heavy stains on your wooden surface, including mold and mildew. Use deck cleaner to apply to the area with a mop or sponge, and scrub with a scrub brush. 

Step 5: Prepare the pressure washer

Attach the 40-degree or 60-degree nozzle to the end of the pressure washer wand. 

Before turning your pressure washer on, make sure you first connect your garden hose to it. Then, turn the water supply for the hose on and start the pressure washer. 

Try spraying a test area (like the edge of a step) before beginning to spray the entire wooden surface so you’re used to the recoil of the spray and the type of stream you’ll be getting out of the nozzle. As needed, gradually increase or reduce the pressure fitting for a powerful clean without damaging the wooden surface. 

Step 6: Wash

Fill your pressure washer soap dispenser with your chosen cleaning solution or deck cleaner. Next, attach the soap nozzle to the end of the pressure washer hose. 

Power up the pressure washer, and using long, overlapping strokes, distribute the water and soap solution across the hardwood surface. It may be easier to work in sections rather than cover the entire wooden surface at once. 

Swap out the soap nozzle with the scrub brush attachment and gradually scrub the cleaner into the surface. Don’t forget to scrub the cleaner in the hardwood’s corners as well as in-between planks and railings. (If you don’t have a scrub brush attachment, a stiff scrub brush works just as well.) Make sure that you do this while the cleaning solution is still wet to avoid streaking; you may add additional water and cleaner if necessary. 

Step 7: Rinse

Change your soap nozzle or scrub brush attachment to be replaced with the 40 or 60-degree tip. 

Start where the wooden surface meets a wall and work your way outward. Maintaining a 24-inch distance between the end of the nozzle and the surface, rinse off the cleaner from the hardwood surface, moving along the grain of the wood with wide, gradual sweeping motions. The goal here is to feather the spray along the length of the wood, parallel to any planks or boards while slightly overlapping strokes. 

After rinsing, you may notice some raised wood fibers present as a result of pressurized water hitting the surface. This is common when pressure washing wooden surfaces and can be resolved by using 80-grit sandpaper to smooth the surface back down after it has dried. Use a clean broom to sweep the area after for a smooth, clean surface. 

Repeat the previous step and this step for each section of the wooden surface you work with. 

Step 8: Apply wood treatments

Applying chemical stripper/brightener

If you decide to use a chemical stripper* to brighten your hardwood surface or remove existing staining or paint before a re-finish, make sure you prep the area by covering any nearby plants with a plastic sheet to protect them first. 

Using the 40-degree nozzle, spray down the surface of the deck one more time with water to ensure it stays wet. 

Add the chemical stripper to the pressure washer soap dispenser, and using the soap nozzle, apply the solution across the surface in the same manner as when you rinsed it earlier. 

Let the solution sit for at least 15 minutes; make sure the solution does not dry during this process.

Replace the nozzle with a 25-degree tip and rinse the area of the solution. Make sure you also rinse off nearby garden plants with the regular garden hose when you are done in case they were exposed to the chemical. 

*Note: According to The Spruce, many chemical stripper/brightener solutions roughen wood fibers, so you may need to sand the wood surface before applying the stain or sealant later. In addition, some deck cleaners contain a chemical stripper component, so you may end up performing this step during step five depending on the solution you picked. 

Applying a stain or sealant

Allow your hardwood surface to dry completely before applying any form of wood stainer. 

After the wood has dried from cleaning or after using the chemical stripper/brightener, you will need to prepare it for a finish or sealant by first using 80-grit sandpaper over the surface to ensure it’s completely smooth. (The process of sanding will also help open up the wood’s pores so that it can absorb the stain or sealant.) For larger surfaces, it may be best to use an orbital sander with a five-inch sanding pad to get the job done quickly. 

Next, use a clean broom to sweep away any excess dust in the area. 

Using a paint roller with extender, dip the roller into a paint tray filled with the staining or sealing material. Apply the stain with the roller over the surface; two thin coats will do. (You can also use a cheaper sponge mop if you do not have access to a roller and paint pan.) To reach hard-to-reach corners or for handrails, use a natural bristle paintbrush. 

Allow the finish to dry for at least 24 hours before replacing the furniture and other objects on top. 

Other Considerations

Although it may seem easy to clean your hardwood deck or patio thoroughly, there are several things to think about before you jump straight into it. You’ll have to consider the type of pressure washer you need for the job; the nozzles you should use; and the cleaning solutions, in order to achieve an effective clean without damaging your deck or patio. 

You’ll also need to consider a sealant or special treatment for your deck or patio after pressure washing if you want to protect it from water damage and rotting or other environmental conditions. 

Pressure Washers for Hardwood Cleaning

Regardless if you plan on buying your first pressure washer for outdoor cleaning or prefer to rent a machine, it’s essential to recognize how to compare your options and know what’s best for your hardwood deck or patio. Different wood types require different pressure washing methods. 

PSI Settings

In general, make sure you use a mid-sized gas or electric pressure washer that offers no more than 2,500 PSI (pounds of pressure per square inch)—although you rarely need any more than 1,500 PSI for wooden surface cleaning. A lower pressure machine means it will take a little more time to clean the wood surface, but the result you get is well worth the effort. 

If you plan on pressure washing softer wood, like cedar or pine, make sure you use a pressure washer that can be adjusted to output 500 to 600 PSI. Harder types of wood can withstand higher pressures, but it’s best not to surpass 1,200 PSI during cleaning if possible. 

Below is a list of a couple of highly-rated pressure washer options suitable for pressure washing hardwood surfaces:

Pressure Washer Features
Sun Joe SPX3000 Pressure Joe 2030 PSI 1.76 GPM Electric Pressure WasherRobust, multipurpose power washer designed to clean various surface types.
Powerhouse International – Electric High Power- Pressure Washer – 3000 PSI 2.2 GPM Powerful and reliable engine for long-lasting use.

Pressure Washer Delivery System

Also, think about the type of delivery system you want your pressure washer to have. Many pressure washer owners prefer to have a machine with downstream delivery rather than upstream. 

The difference is this: With downstream delivery, cleaners are added to the pressure washer’s hose after the water has gone through the pump, making your choice of cleaning solution a little more flexible since there’s no risk of damage to the internal components of the machine. 

Upstream delivery, on the other hand, feeds the cleaner through the pressure washer’s pump, so you have to be more careful when selecting your cleaning solution so as not to end up damaging your pump with harsh chemicals such as bleach or ammonia. 

If you plan on renting your pressure washer—or if this will be your first pressure washer purchase—try to look for downstream machines; they are more user-friendly and require less maintenance in general. 

Pressure Washer Nozzles & Attachments

For effective pressure washing, use a fan tip that offers a 40 to 60-degree spread to lessen the degree of water pressure on the hardwood surface to avoid damage. 

You will also need a soap nozzle to dispense the wood cleaner in addition to a scrub brush attachment. 

Cleaning Solutions for Hardwood

There are several types of wood deck cleaners available. They can be found in three categories:

  • Chlorine Bleach Cleaner* – Chlorine cleaners are usually not recommended, as their chemical base will actually damage the wood’s integrity over time and create an unwanted bleaching effect. In addition, the bleach found in this solution can cause a rusting effect on any screws or nails in your patio or deck. 
  • Oxygen Bleach Cleaner – Oxygen bleach cleaners are effective in removing mold and mildew from hardwood surfaces when mixed with water. Some multipurpose wood cleaners, such as Simple Green Oxy Solve Deck and Fence Pressure Washer Concentrate, can also aid in the removal of oils and grease, and tree sap. 
  • Oxalic Acid-based Cleaner – While this cleaner is not effective in removing mold and mildew, it is useful in eliminating tannin stains, which are naturally occurring dark, reddish-brown stains that can be found in redwoods, cedars, and oaks. This cleaner is ideal if you want to both clean and brighten your wooden surface. 

*Note: Be mindful of the type of chemical cleaners or treatments you plan on using together to avoid adverse chemical reactions. For example, avoid using bleach with deck cleaners containing oxalic acid, sodium hydroxide, sodium hypochlorite, or sodium percarbonate. 

Ideally, you should stick with either an oxygen bleach cleaner or oxalic acid-based cleaner. You can find effective variants of both cleaners on Amazon for a reasonable price. 

Wood Treatments

Chemical Stripper & Brighteners

Some deck cleaners feature chemicals designed to help brighten wooden surfaces which can also be used with pressure washers. For example, some of the most common chemical stripper/brighteners are combined with oxalic acid-based wooden deck cleaners. For this reason, in many cases, you may find that you can both wash and strip your wooden surface all at once. 

Of course, some wood brighteners can also be found as an individual solution, such as #1 Deck Wood Brightener

Wood Staining

There are four types of staining treatments for hardwood surfaces:

  • Clear or Transparent (also referred to as “natural” treatment) – Clear or natural staining offers the results you would imagine would come from this treatment. Finishing as a clear coating, this treatment option shows the original wood underneath while forming a protective layer over it. It’s ideal if you’re attached to the way your deck or patio’s wood currently looks like. However, it is not as UV resistant as solid staining and therefore, can begin to degrade under extreme light exposure. 
  • Toner – Toner stains help bring out the look of your wood’s grains, giving it a beautiful, accented feature. 
  • Semi-Transparent – Semi-transparent staining does the opposite of toner staining as it helps cover up or mask grains for a more muted effect. 
  • Solid – Solid treatments cover the wood completely, resulting in a look completely different from the original surface. (It is almost the equivalent of using straight paint.) It offers the most reliable protection against UV rays, protecting the wood from experiencing warping or graying from extreme heat exposure.  

Regardless of the type of stain you choose, make sure that you end up going with an oil-based stain that is water-repellent. This will ensure that the wood is also protected from water damage. 

Wood Sealant

If your wood staining solution does not feature water-repellent properties, you will need to find an appropriate sealant to ensure that your hardwood surface stays protected. With the right type of sealant, you can avoid swelling, warping, or rotting damage in the long run.  

Outside of stain-sealant combinations, there are a couple more wood sealant options to choose from: 

  • Linseed or Tung Oil – These sealant options are best for dark-grained woods such as walnut and mahogany. 
  • Polyurethane, Varnish, or Lacquer – These sealants are best for lighter colored woods, such as pine or ash. 
    • Polyurethane – Polyurethane sealants offer users the flexibility of choosing your own finish effect, whether you prefer a soft sheen or a high gloss. 
    • Varnish – Marine varnish, specifically, contains properties that help protect hardwood from UV damage. 
    • Lacquer – This sealant is more commonly used with wooden furniture, and offers a scratch-resistant finish on deeper-toned wood. 

Once you’ve figured out which pressure washer, nozzles and attachments, cleaners, and wood treatments are best for your hardwood deck or patio, you’re ready to start cleaning!

Final Thoughts

Without regular upkeep and cleaning, a nice deck or patio can quickly begin to look worn down and withered over time. You can keep your outdoor wood surface clean and looking great all-year-round with routine pressure washing and re-treatment at least every two to three years! 

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