Safe and Proper Wood Deck Pressure Washing Practices

Avoid Irreparable Damage with the Right Cleaning Processes, Tools and Techniques for Wood Decks

Thinking about calling a company or doing your own deck pressure washing? While harder surfaces like brick and concrete can handle direct pressure, wood deck surfaces must be cleaned with an added level of care and caution. Using the wrong chemical or technique to pressure wash your wood deck can strip it and ruin it.

Let’s get down to basics on properly and safely pressure washing wood decks.


When to wash my wood deck?

Wood decks are exposed to all weather elements throughout the year. Over time, sealants tend to wear down, and algae takes root. The decking will start to inherit a green or aged black look and can become extremely slimy and slippery after it rains. When it gets to that point, it’s time to have it washed.

Decks can be pressure washed at any time of the year. For those who enjoy their deck during warm weather, an annual spring deck wash is advisable. Be sure to book a pressure wash several weeks ahead before the spring rush of customers occur.

If you’d like to stain, paint or seal your deck wood, a pressure wash is a great way to prime the deck surface for even coverage. Cleaning the deck will be necessary to remove any organisms, dirty and debris stuck to the wood.

When following the deck wash with paint, stain or sealant, be sure to choose a week where you have several consecutive days of dry, sunny weather. You will want the deck to dry at least 24 hours (48 hours is better) to allow the wood to dry completely before applying any products to ensure good adhesion for sealants or stains. If the wood decking is not thoroughly dry prior to painting, moisture trapped in the wood will leach from the wood, causing the paint to peel off.

Prior to cleaning, we remove all the rugs, furniture, and plants and sweep the deck clean.We also wet any adjacent plants that cannot be removed to prevent chemicals from sticking to them.


Choosing Proper Cleaning Agents for Pressure Washing Decks

The first step toward safely cleaning the deck is using the appropriate cleaning agent (detergent) for the correct amount of time. Most of the work should be done by the detergent. The pressure washing equipment should not be used to blast the grime off the wood. Doing so will strip the wood decking and leave etch marks, leaving furry strips of raised wood grain. It will look terrible and to repair it would mean replacing those boards.

Depending on the type of wood, detergents, bleach mixes, and custom chemical solutions can be used to get the wood cleaned. These chemicals should be chosen carefully to make sure they are used for the proper application, type of deck wood, and won’t damage existing sealants, paints or stains. These agents will kill whatever organisms are growing in the wood and loosen dirt. It is extremely important to only use these agents for the recommended application time to avoid chemical stains and/or deeply damaging the wood.

The detergent is applied all over the deck for complete coverage, including pickets, gates and handrails. Typically, it is allowed to set and work for 10 to 15 minutes after application, depending on the agent.


The Right Techniques for Pressure Washing Decks

In extremely dirty areas some or all parts of the deck may benefit from a scrub with a bristle brush. We use synthetic bristle brushes because natural bristles can be corroded by certain cleaning agents. The brushing motion helps to activate the cleaning agents and jostle harder stuck-on residues and particles from the surfaces.

Typically, the agents aren’t allowed to dry on the surface, and it may be necessary to mist the surfaces to keep them wet prior to rinse. Often we can see the agents starting to work within a few minutes of application. Once necessary scrubbing is completed, it’s time for a rinse.

A 25 degree nozzle is advised for wood deck cleaning. It provides enough concentrated spray pattern to clean wooden decks without scarring them when used properly. The nozzle should be at least 4 inches from the surface of the deck to avoid applying too much pressure, and the pressure output should not exceed 1,500 psi.  Using the incorrect nozzle or getting the nozzle too close to the wood is the most common cause of damage to the decking.

The wand is moved back and forth across each plank following the grain of the wood. The technique looks similar to a long sweep of the wood. The technician is always on the move, making sure to provide a continuous, even cleaning across each plank. Following each swing we lift up with the wand to avoid leaving stop and start mark lines which can be seen even after staining. The majority of the algae and dirt in the wood will be lifted during this process and will be scattered around the deck.

A final, gentle rinse will remove any remaining cleaning and particles that remain on the deck. This is typically done with a fanning motion. The adjacent plants should also be given another rinse to remove any chemicals or residue.

Once this is complete, conduct a final inspection of the deck to ensure all parts of the deck have been effectively and thoroughly cleaned.


When to Call a Pressure Washing Company

Pressure washing a deck is a task within the ability of many homeowners. However, if you have never cleaned your wood deck before, or don’t own the right equipment, we recommend calling a professional pressure washing company to do it for you.

We find that customers spend the entire weekend trying to hunt down the right chemicals and rent, borrow, or buy a pressure washing machine. Then, trying to get the job done in their limited remaining time, they accidentally splinter their deck wood, causing unsightly damage.

Another circumstance we see is that customers spend a lot of time working in one area, only to discover their entire house, windows and roof need to be cleaned too. Overwhelmed by the amount of work, tools and time needed to complete the whole job, they call us to do it for them.

Pressure washing a wood deck is not an efficient use of their time or money for most homeowners, especially when an experienced company can clean their deck (and entire home) properly and quickly.


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