Pressure-Washing a Deck
Get the expert knowledge you need for power washing a deck.
Power washing a deck seems like a simple task. Just point and shoot, right? But the reality is that without the right equipment and knowledge, power washing your deck can potentially cause costly or even irreparable harm to the wood.
Choosing the right power washer and operating it at the correct pressure setting are the first keys to correctly power washing a deck. Power washers can be powerful enough to carve into brick or gentle enough to remove a few cobwebs.
Refinishing a Deck
A deck can be a valued extension of the home, but time and the elements will take their toll. If it has been a few years or even decades since your deck has been given the attention it deserves, it may be time to refinish with necessary repairs, a thorough cleaning and a fresh coat of paint or stain.
Determine Your Needs
A deck that is just a couple of years old or has received regular maintenance is still likely to benefit from a good cleaning. An older deck may need repairs to railings or steps, replacement of split or splintering planks and decisions will need to be made regarding the type of stain used to protect and beautify the structure.
Select a Cleaning Solution
Diluted bleach is a popular choice for deck cleaning, but isn’t necessarily the best choice. Over time, stain is more likely to fade or discolor and bleach can hasten the degradation of the wood. Instead, select a cleaner formulated specifically for deck cleaning and follow manufacturer instructions regarding dilution and application.
Deck cleaner can be spread by using a brush or broom to sweep across the surface or applied using an inexpensive tank sprayer as shown here. Make sure all edges, corners and gaps are treated as will as the deck surface. Follow manufacturer instructions regarding use, but in most cases, the solution should be left to soak on the wood for a period of time before continuing.
A pressure washer is a powerful tool for cleaning a deck. Take care to select a nozzle appropriate for the job. Spray nozzles are categorized by the angle of the spray. A zero degree “red tip” provides the most powerful stream, but can damage the soft wood. Consider a nozzle with a spray angle of 25 or even 40 degrees to clean your deck without scarring the surface.
Repeat Cleaning Process, If Necessary
If it has been a long time since the deck has been pressure washed or has been subject to unusual mildew or staining, a second application of deck cleaner and another round of pressure washing may be needed for a thorough cleaning. If you were on the fence about applying a new stain to the deck, it may be easier to decide once you’ve seen it at its cleanest.
Selecting a Stain
If the lumber used to build your deck looks just perfect in condition and color, you may elect to apply a clear sealer. For most of us, the deck will benefit from a little color, but the choice of stain used will vary with preference and deck condition. A deck that is in good condition with minimal splintering and uniform color throughout is a good candidate for a semi-transparent stain, which soaks into the wood and leaves the grain of the wood visible. Solid stains, as we use on this project, coat the surface of the wood like paint and will hide replaced lumber and minor weathering. If the condition of the wood is especially weathered, a resurfacing stain containing grit is a forgiving choice and can hide cracks as deep as 1/4".
Plan to stain once deck is completely dry and no rain is in the immediate forecast. Tape off edges as needed and make sure no debris is present. A paint pad or roller can be used to apply stain to the deck, but care should be taken to apply evenly. Solid stains are more forgiving, but uneven application or “touch up” spots will stand out when using semi-transparent stains.
For cleaning a wooden deck, you'll be best served by using the lowest pressure setting that's still effective. For soft woods like cedar or pine, this is usually about 500 to 600 psi. For harder woods, it can go up to 1200 to 1500 psi.
Choose the right tip to use as well. For wood cleaning, generally a fan tip or rotating tip (used carefully) will work best. Remember to always start the water pressure in a safe area pointing away from people and glass windows, and start at least two feet from the wood deck, then feather the pressure into range from about a foot to 18 inches from the deck. Never get closer than 12 inches from the deck unless you're using low pressure.
Remember to start in an area that would be easy to repair or replace. For example, try starting on a stair tread, which would be simpler to replace than an entire deck board. Once you're sure you've got the right pressure setting, work from the house outward and be sure to keep a consistent distance as you hold your arm steady and sweep, working with the grain of the wood. If the washing results in raised soft wood fibers, you will need to sand before staining your newly cleaned deck.
See also: Deck and Patio Design Ideas