September 12, 2025 · 8 min read
How Often to Pressure Wash Your House (By Region)
Of every question we get on a daily basis, the most common is also the simplest: how often should I have my house pressure washed? The short answer is once a year for most homes — but the honest answer is that climate, surroundings, and siding type all change the math. After 15 years of cleaning homes in every climate in the United States, here is the schedule we actually recommend, broken down by region and by what we see on real properties.
The Quick Answer
Most single-family homes benefit from a professional soft wash every 12 to 18 months. Homes in heavy shade, near the coast, or in the humid Southeast often need it annually. Homes in dry, sunny climates and on open lots can sometimes stretch to 24 months. If you can already see black streaks, green growth, or a dingy film on your siding, the answer is now — those contaminants are eating into your paint and substrate every day they stay there.
Region 1: The Humid Southeast (FL, GA, AL, MS, LA, SC, NC, TN, AR)
Annual cleaning is non-negotiable. The combination of year-round warmth, high humidity, and frequent rain creates ideal conditions for mildew, mold and gloeocapsa magma (the blue-green algae responsible for those ugly black streaks on roofs and siding). Homes shaded by oak, magnolia or live oak — which is most of them — often need a wash every 9 months. If you live near the coast, salt deposits compound the problem and require an annual rinse even on the cleanest-looking homes.
Region 2: The Pacific Northwest (WA, OR, Northern CA, ID)
Annual cleaning, with special attention to roofs. The mild, wet climate is moss heaven. Moss on shingles and pavers can take hold in a single winter and is structurally damaging — it lifts shingle edges and traps moisture. Annual soft-wash treatment of the roof and house, paired with zinc strips at the ridge, is the gold standard. Decks need cleaning every 12 months and re-sealing every 24.
Region 3: The Northeast (NY, NJ, PA, CT, MA, RI, VT, NH, ME)
Every 12 to 18 months, ideally in late spring after the worst of the pollen and salt-spray season. Winters bring road salt and grime; spring brings pollen; summers bring algae and mildew on shaded north walls. A spring clean removes a winter's worth of contamination and protects your siding through the next freeze-thaw cycle.
Region 4: The Midwest (IL, IN, OH, MI, WI, IA, MN, MO, KS, NE, ND, SD)
Every 18 months on average. Drier than the South and East, with more extreme temperature swings. The biggest issue is pollen, road dust, and north-side mildew on shaded walls. Spring or early summer is the right window — a clean home before the pollen settles also keeps your HVAC intake cleaner all year.
Region 5: The Mountain West (CO, UT, NV, MT, WY, ID)
Every 18 to 24 months. Dry air dramatically slows mildew growth, but UV and dust take their toll on paint and stucco. The biggest issue here is window streaking from sprinkler over-spray and oxidation buildup on aluminum gutters. Plan for a clean every other year and a one-off gutter brightening in between.
Region 6: The Desert Southwest (AZ, NM, West TX, Southern NV, Southern CA)
Every 24 months. Heat and aridity keep biological growth to a minimum, but oxidation, dust, and minerals from hard well water build up steadily. A biennial clean keeps stucco bright and prevents the chalky oxidation that gradually dulls paint.
How Siding Material Changes the Schedule
Vinyl and Hardie hold up best to long intervals between cleanings — they shed dirt and resist staining if washed annually. Painted wood (cedar, T1-11, lap siding) is the most vulnerable and benefits from an annual clean to prevent paint failure caused by mildew penetrating the paint film. Stucco and EIFS hold mildew aggressively on the north side; even in dry climates these homes do best with an 18-month cycle on shaded elevations.
What About Brick and Stone?
Brick is forgiving but mortar joints harbor mildew that streaks downward over time. Every 24 months is appropriate for most brick homes; coastal or shaded brick benefits from annual rinsing. Natural stone needs a low-pressure, pH-neutral clean — never high pressure or acidic chemistry.
Warning Signs You Have Waited Too Long
- Visible black streaks on north-facing walls — gloeocapsa magma has taken hold.
- Green or yellow fuzz at the bottom course of siding — algae feeding on moisture from the splash zone.
- Tiger striping on aluminum gutters — acid rain oxidation that requires brightening, not just washing.
- Spider webs and wasp nests in every soffit corner — a sign no one has cleaned in 2+ years.
- Paint that looks dull, chalky or faded — oxidation that a soft wash can often partially restore.
- Black spots on concrete walkways or driveway — embedded algae that worsens with every rain.
How to Make a Cleaning Last Longer
Three simple steps extend the life of a professional clean: keep gutters flowing so splash-back doesn't re-soak siding, trim back tree branches that touch the home, and ask your contractor to apply a residual surfactant package that continues to inhibit mildew for several months after the visit. Combined, these can stretch a 12-month cycle to 18 and an 18-month cycle to 24 in most climates.
The Bottom Line
Annual is right for most of the country. The cost of an annual soft wash ($279–$899 for most homes) is a tiny fraction of the cost of repainting or re-siding a home — and those are exactly the expenses you avoid by keeping the exterior maintained. Call AquaShine at (626) 618-8360 for a free, no-pressure quote tailored to your home and your climate.