How to Pressure Wash A Deck


Decks are platforms that serve structural, aesthetical, and architectural functions. It is similar to a floor, only elevated and is adjoined to a building. Decks, wooden ones significantly add more beauty to outdoor living. Decking materials are either wood (treated lumber) or composite materials- composite materials are made up of fiberglass or a mixture of plastic and wood fibers.

The best method to clean a wooden deck is by pressure washing it. This is because some dirt can be stubborn and caked-on to remove with only detergents or any other type of cleaning agent suitable for woods. Still, the high-pressure jet of fast running water that comes out from the pressure washers hits the dirty surface and washes out any form of dirt present.

Pressure washing uses high pressure to direct a stream of hot or cold water in cleaning exterior surfaces. A pressure washer (or pressure washing machine, as it will be simultaneously referred to in this text) is simply a pump powered by an electric motor. It works by taking in water from a tap or source; the pump accelerates the water to high pressure and then pushes it out from a hose at full speed. The pressure washer serves as a mechanism to take off deep-seated diets and other contaminants. Often, a pressure washer can effectively clean with just a little water. When placed too close to the deck’s face or applied with too much pressure, it can corrode the wood.

Power in a pressure washer is regulated by two major factors- the water flow and the PSI (pounds per square inch). Knowing the right PSI to use is very important in pressure washing. When the amount of pounds per square inch is high, the force of the water will also increase. If the GPM is high, the cleaning appears to be faster and vice versa.

There are two significant types of Pressure Washing machines- the the Gas Pressure Washing machines and Electric Pressure Washing Machines. Electric pressure washers require electricity to work, usually run on a lower PSI, and run quieter than gas pressure washers. Gas pressure washers need fuel to operate and run a much higher PSI than Electric Pressure Washers.

There are some main parts of a pressure washer; Water Inlet, Cleaning Attachments, Water pump, Electric motor or Gas engine, High-Pressure Hose. For brief descriptions of these parts, checkout Parts of A Pressure Washer

Pressure washers come in different tips of spray nozzles. Spray nozzles are responsible for creating the water stream’s pressure that hits the surface to be cleaned. There are varieties of nozzles in coded-color types to choose from. When selecting the right nozzle type to use, the primary steps to guide are common sense (gut). It is also advised to start with the nozzle type with the most expansive spray area (40-degree spray nozzle) and start with small sizes to be cleaned.

  1. Red zero-degree nozzle: It is used with caution from any distance and is built with an outburst of high force to remove dirt from any surface.
  2. Yellow 15-degree nozzle: has a narrow yet rugged span, creates a span of about 15 degrees area of water flow. It is also often used to prepare surfaces for painting.
  3. Green 25-degree nozzle: This is the most common type of spray nozzle used for all-purpose cleaning surfaces. It creates a 25-degree wide area of water spray.
  4. White 40-degree nozzle: creates a wide area span of about 40 degrees of water flow and is mostly for cleaning fragile surfaces. It produces a gentle mist and can also be used to rinse off detergents.
  5. Black 65-degree nozzle: is the lowest pressure nozzle with the highest opening. It uses this to reduce velocity and increases pressure in the hose. This pulls detergent in and makes it faster and easier to clean.

Wooden decks accumulate a lot of grime when left uncleaned for a long time. Cleaning of decks is part of its maintenance and require the use of a pressure washer, effort) and other deck cleaning materials. Deck cleaning materials come in varieties; detergents, chemical solutions, and bleaches. Keeping it clean can prevent it from rotting, splintering, and warping. Cleaning a deck can take a lot of time, and below are steps/techniques on how to pressure wash a deck.

In Preparation of Pressure Washing

The equipment used mostly in pressure-washing a deck is the Pressure washer (Power washer). Optionally, sheets of plastic, deck stripper, orbit sander, or sandpaper can be used alongside the pressure washer.

After getting a suitable pressure washer, it is necessary to prepare the work area and have safety precautions. Use safety glasses for eye-protection should in case of particles fly off from the surface of the deck. Make sure children and delicate objects are not around the area that is to be pressure washed. Wear thick, firm clothing to avoid loosening up while cleaning. Cover nearby plants and shrubs with an awning cloth.

Start your deck cleaning right by resetting your nails and looking out for protruding ones. Since the deck furniture is mostly outside, it absorbs the rainwater, expanding the deck’s pins during rainfalls. And when the wood dries, it shrinks around the wood. This forces the nails upwards and can cause accidents in the process due to nails shooting out above the surface of the deck. Resetting a nail involves using a drift pin and hitting the pin in the part where the nail shoots until the nail is dislodged alongside the wood it is on.

The next step is cleaning the wood with cleaners. You might think this is entirely the job of a pressure washer, but if the surface has accumulated a lot of mildew and grime over time, washing the wood with detergents or other recommended wood cleaners is necessary. It helps pressure washers perform an even better job. It helps to use a pump sprayer for a large area of the deck to be covered. Spray the entire deck with the cleaner, leave to soak for some minutes- 15 minutes is recommended to allow the cleaner soften the dirt on the surface. Then, use a deck-scrubbing brush to remove the dirt from the wood by rinsing with a hose or by beginning to pressure-wash.

How to Clean with A Pressure Washer

The pressure needed to wash is rarely more than 1500 pounds per square inch (PSI). Cleaning the deck by washing with a pressure washer machine requires technique. To test it first, start with using 500- 600 PSI, till it is set to the conventional mode for the operator to use.

After setting the spray nozzle to a wide-angle (40-60 degree), hold the spray nozzle around 24 inches up the deck before using the trigger; after that, lower it to a unit of 12 inches higher up the wooden platform.

Clean in a lateral sweeping direction, overlap each spray stroke not to show lines or marks of the sweeping. Instead of a direct burst of water to clean a spot, use multiple sweeps to clean. Be sure not to focus on one area for more than a second. Keep the tip away by at least a foot away from the surface to avoid damaging it.

After pressure washing, the deck should be allowed to dry for 24-48 hours. Ideally, a pressure washer is not designed to corrode or damage the wood, but the wood can swell when wet, causing a rough surface resulting from getting wet. Ensure the wood is dry before you begin to sand.

Sanding is smoothening the deck surface with sandpaper or a mechanical sander. For wooden decks after pressure washing, a random orbit sander is recommended.


Be sure to test the pressure washer before using, as a washer with a high PSI can damage the wood and chip away the deck gradually. Test it on the other side of the deck first, where damage won’t be visible. Read the instruction manual of your Pressure Washer thoroughly before you begin work.