Staining over dirty or weathered wood traps contaminants under the finish. The stain may look fine for a few weeks, then peel in patches. A proper wash removes mould, dirt, and grey oxidation so the product bonds to clean wood — not to debris.
Power washing before staining removes the things that cause early failure: surface dirt, mildew spores, UV-oxidized grey wood fibre, pollen, previous sealer residue, and organic buildup from leaves and debris. Stain bonds to the first thing it contacts. If that thing is a layer of grime and oxidation, the bond is with the grime — not the wood.
The step most contractors skip: brightening
Washing opens the wood and raises its pH. Without a brightening step — applying a wood brightener that neutralises the pH and closes the grain properly — the wood surface is chemically unbalanced when you start staining. Penetrating oil-based stains absorb differently in high-pH wood. The result is uneven colour and shorter life.
We apply a wood brightener after every wash, let it work for the recommended dwell time, then rinse. It adds time to the prep day. It's also the difference between stain that lasts 3–5 years and stain that looks patchy by year two.
What power washing alone doesn't fix
A pressure washer can't remove deeply embedded grey oxidation from wood that's been neglected for several seasons. For those surfaces, we use a wood cleaner before washing — a chemical treatment that breaks down the oxidised layer and lets the wash do its job. If we show up and find a deck that's heavily greyed, we'll adjust the scope and cost before we start.
Why we schedule 24–48 hours between washing and staining
After washing, wood needs time to dry fully — not just surface dry, but through the grain. Staining over wet wood is the same problem as staining over high-moisture new lumber. The stain sits on top of trapped water and doesn't bond. We schedule the wash and the stain on separate days, with the interval depending on sun, temperature, and humidity.
When not to hire us
If you've had your deck recently power washed by someone else and it was done with proper brightening, we don't need to wash it again. Tell us when it was done and what was used. We'll assess whether the surface is ready or whether a light cleaning is needed before we stain.
