Flagstaff's 6,910-foot elevation and four-true-seasons climate give homeowners unique exterior cleaning challenges that don't exist in Phoenix or Tucson. Ponderosa pine pollen, red volcanic cinder, monsoon mud, snow mold, and wildfire soot all leave their mark on your home in different months. Here are seven seasonal pressure washing tips every Flagstaff homeowner should keep in mind.
If you only wash your house once a year — which is plenty for most Flagstaff homes — do it in late May or June, right after ponderosa pine pollen season has wound down. Pollen leaves a yellow film on horizontal trim, lower siding, and outdoor furniture that bakes into finishes under summer sun if left untreated. A late-spring soft wash removes the pollen while it's still loose and leaves your home protected through monsoon.
Monsoon storms from July through September wash red volcanic cinder, ash, and mud across every concrete driveway and sidewalk in Flagstaff. By late September, most driveways have a noticeable pink-orange tint from iron oxide in the cinder. A fall driveway cleaning resets the concrete to its original gray before winter freezes anything in place.
Pressure washing in Flagstaff doesn't work below freezing — full stop. Water that contacts a 30-degree surface freezes before it rinses, and ice can lift mortar, crack shingles, split deck boards, and damage outdoor electrical. The practical service season is April through October. Any company that's willing to wash your home in November or January is willing to damage it. Wait for warmer weather.
If you're tempted to pressure wash your own wood deck, do the pinky test first: press your pinky nail into a hidden corner of decking. If the wood dents easily, it's soft enough that almost any pressure washer setting will damage it. Pine and cedar are particularly vulnerable. Even with the right nozzle, an inexperienced user can fuzz the grain so badly the deck has to be sanded before staining. If your deck is wood and it needs more than a hose rinse, hire a pro who can dial in PSI for your specific boards.
Snow mold and mildew thrive in shaded, damp areas, and the underside of decks and the shaded side of fences in Flagstaff stay damp for months after snow melts. These hidden surfaces are spore reservoirs. Spores spread from there back to the visible deck and fence surfaces year after year. A spring deck and fence cleaning that includes underside treatment dramatically slows regrowth.
Even soft wash detergents can stress plants if they're sprayed onto dry foliage. Wet plants don't absorb cleaning solution. Before any wash — whether you DIY or hire a pro — thoroughly wet down all plants, shrubs, and lawn within 10 feet of the work area. We do this automatically on every job, and we rinse again at the end. If a pro you've hired doesn't pre-rinse, ask them to.
Long Flagstaff winters give roof algae and lichen ideal conditions to grow on the shaded north slopes of roofs, especially in heavily wooded neighborhoods like Cheshire, Continental Country Club, and Forest Highlands. By spring, you can often see the black streaks from the street. Roof algae shortens shingle life and traps moisture against the roof deck. Soft washing — never pressure washing — is the only correct method. Done right, it kills the algae down to the root and the streaking is gone for years.
Late May or early June, right after ponderosa pine pollen season has wound down. The weather is consistently above freezing, the pollen film is still loose, and there's plenty of dry weather for your home to fully dry. The second-best window is mid-September, after monsoon season ends and before the first hard frost.
Most homeowners can safely rinse pollen off composite decking with a garden hose. But cleaning a wood deck with a pressure washer is one of the most common DIY mistakes we see. The wrong PSI will shred soft pine, fuzz cedar, and gouge boards in a way that's hard to fix without sanding the whole surface. If your deck is wood and it needs more than a hose rinse, hire a pro.
Most window screens benefit from being removed and rinsed flat with a garden hose. For window glass, a soft microfiber and a vinegar-water solution removes cinder dust without scratching. Avoid using a pressure washer on window seals — high pressure can force water past the seal and into the frame, leading to fogged double panes and water damage.