How to Pressure Wash Wood & Composite Decks

How to Pressure Wash Wood & Composite Decks

Decks can be a major upsell in residential pressure washing—but only if you do them correctly. Wood and composite decking require very different cleaning methods, and doing it wrong can cost you a job—or worse, damage someone's property.

Cleaning Wood Decks (The Right Way)

Wood surfaces are very sensitive to pressure. While blasting it with high PSI may look clean in the moment, it will damage the wood fibers and leave the deck with a fuzzy texture known as “furring.”

Correct Method for Cleaning Wood

  1. Pre-treat with Sodium Percarbonate: This oxygen-based cleaner lifts dirt and organic growth from the wood without harsh pressure.
  2. Wash at low pressure: Make one continuous pass with the wand. Do not stop and restart every few feet—this creates visible stripes in the wood.
  3. Follow up with Oxalic Acid: This brightens the wood and neutralizes the cleaner, restoring the wood’s original tone.

Note: Let the chemicals do the work. Your PSI should stay low—ideally around 800–1000 PSI max, using a wide fan tip.

Properly cleaned wood deck using the two-step method

Why We Defer All Wood Cleaning Jobs

We’ve made the decision to pass on all wood deck jobs. Here’s why:

  • They are time-consuming and lower margin
  • The risk of damage is higher
  • Results are highly variable depending on the wood condition

Instead, we build relationships with other pressure washers in our area who specialize in wood cleaning. We refer all wood jobs to them, and in return, they often send us house and concrete wash leads. Everybody wins.

Cleaning Composite Decks

On the other hand, composite decks are incredibly easy to clean. They use the same cleaning process and solution as a standard house wash:

  1. Apply your house wash mix (typically sodium hypochlorite and surfactant via downstream or soft wash system)
  2. Let it dwell 5–10 minutes
  3. Rinse thoroughly with low pressure

Composite doesn’t absorb water like wood and holds up very well during cleaning. These are quick, profitable, and low risk.

Key Takeaways

  • Never blast a wood deck with high pressure
  • Use sodium percarbonate and oxalic acid for wood
  • Always make full passes—no start-and-stop stripes
  • Refer wood jobs if you aren’t confident
  • Composite decks = easy profit