People ask us this every week. Short version: in Seattle you should plan to power wash more often than anywhere else in the country. The combination of moisture, evergreen trees dropping needles, and 9 months of overcast skies is basically a greenhouse for mildew, algae, and moss. The good news is that most homes can stay on a simple yearly rhythm and never deal with the heavy buildup that takes a full day to chip off.
The honest schedule
Here is what we recommend for the Greater Seattle area, broken down by surface. Times are in years.
- Driveway and front walkway: every 1 to 2 years. Sooner if you have a tree dropping sap or a north-facing slab that holds moisture.
- House siding: every 2 to 3 years. North and west walls grow algae fastest because they get less sun.
- Wood deck: every year, ideally in late spring. Wood traps moisture and grows mildew within months.
- Composite deck: every 1 to 2 years. Composite resists mildew but still gets a film.
- Patio and concrete pavers: every 1 to 2 years. Pavers grow weeds and moss in the joints if left alone.
- Fence: every 2 to 3 years.
- Roof: only when needed. Most asphalt-shingle roofs last longer if you treat moss with a soft wash instead of pressure.
Best time of year to do it
Late spring through early fall. The drier the weather, the better the cleaner stays clean. Washing in March will look great for two weeks and then start collecting fresh grime once the rain returns. Washing in May or June gets you the longest clean window before fall.
That said, we do power washing year round. If you are listing your home in February or hosting an event in October, the season does not matter. We will get it clean.
How to tell it is time
You do not need a schedule on the wall. You just need to look. If any of these are true, it is time:
- Black or green streaks running down siding under gutters
- The driveway looks darker than the slab next to your neighbor’s
- The deck feels slick when wet
- Moss is filling the joints between pavers or bricks
- You are about to list, sell, host, or paint
What homeowners get wrong
The most common mistake is waiting too long. Once mildew has been growing for 3+ years, the roots are deep enough that even a heated power wash leaves a faint shadow. Cleaning it on a yearly rhythm is way easier than catching up after 5 years of neglect.
The second mistake is renting a cold-pressure rig from the hardware store and going at the siding yourself. That ends in stripped paint, dented vinyl, water inside the wall cavity, or a fall off a ladder. We have rebuilt enough trim from DIY washing jobs to know it is not worth the savings.
What it costs to keep on a schedule
For an average Seattle single-family home, a yearly driveway and walkway clean usually runs a few hundred dollars. Adding siding once every couple of years is another few hundred. The deck adds a bit more. Over 5 years, the math always wins compared to repainting siding or repairing wood that mildew has eaten into.
Getting on the rhythm
Most of our power washing customers in Seattle just call us once a year and we walk the property and clean what needs cleaning. No contract, no membership. Free quote any time on our power washing page or 206-501-2223 to talk to someone real.
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