What is actually growing on your house
The green film on a north wall is algae. The black streaks running down a roof are a different algae that feeds on the limestone filler in shingles. The grey-black spotting on a fence or a wood deck is usually mildew. What all three need is moisture, warmth and shade, and our climate supplies all three for most of the year.
This matters because growth is not only cosmetic. Living organisms hold moisture against the surface they occupy. On wood that means accelerated rot. On painted surfaces it means adhesion failure and early peeling. On mortar it means slow erosion. On concrete it means the slick film that makes a driveway genuinely dangerous after a rain.
Removing the organism, rather than just the visible layer, is what determines how long a wash lasts. Pressure alone removes the appearance. A cleaning solution with dwell time removes the organism, which is why a soft wash stays clean far longer than a high-pressure rinse of the same wall.
A realistic schedule by surface
- House exterior soft wash: once a year for most homes. Heavily shaded elevations sometimes every eight to ten months.
- Driveways and sidewalks: once a year in open sun, twice under tree cover.
- Wood decks: annually, ideally before restaining.
- Fences: every one to two years, depending on shade and sprinkler exposure.
- Roof treatment: only when streaking appears, typically every three to five years, and never with pressure.
- Commercial sidewalks and dumpster pads: quarterly to monthly, depending on foot traffic and food service.
These are starting points, not rules. Two houses on the same street can need different schedules because one has a live oak on the north side and the other does not.
Read your own property first
Walk the perimeter and note four things. Which walls get direct sun and which stay shaded all day. Where trees overhang the roof or the driveway. Where sprinklers hit the house, a fence or a walkway. And where water sits after rain instead of draining.
Those four observations explain nearly all of the variation in how fast growth returns. A north wall under a tree canopy with a sprinkler head aimed at it will be green again in six months no matter how well it is cleaned. Fixing the sprinkler direction does more for that wall than an extra wash.
The same logic applies to driveways. A driveway under heavy canopy collects leaf litter that decomposes, holds moisture and feeds algae. Blowing it clear regularly extends the interval between cleanings measurably.
The best time of year to schedule
Late winter through spring is the most useful window here. Growth from the previous year is at its peak and visible, temperatures are workable, and cleaning before the humid season starts gives the surface a clean baseline going into the months when growth accelerates.
If you are painting or staining, cleaning is not optional and the sequence matters. Surfaces need to be cleaned and then fully dry before coating. On wood that usually means several days, longer in humid weather. Coating over a surface that still holds moisture or still has living growth on it is the fastest way to a failing paint job.
Before a home goes on the market, a full exterior wash is one of the highest-return items available. It changes the first photograph and the first impression at the same time, at a fraction of the cost of any other exterior improvement.
What is reasonable to do yourself
Some of this is genuinely DIY-friendly and some of it is not. The dividing line is whether a mistake is reversible.
- Reasonable: rinsing a small patio, cleaning outdoor furniture, blowing leaf litter off flatwork regularly.
- Risky: any wand work on siding, where close-range pressure forces water into the wall.
- Risky: wood decks, where high pressure raises the grain permanently and leaves wand marks.
- Do not: roofs, where pressure strips granules and shortens shingle life by years.
- Do not: soft brick, older mortar and stucco, where pressure erodes the surface.
The most common repair call we get is not for a dirty surface. It is for concrete that was cleaned with a hand-held wand and now carries permanent stripes, because a wand cannot be held at a perfectly consistent distance and speed by hand. A surface cleaner attachment solves it, and it is the single piece of equipment that separates a professional flatwork result from a rental unit result.
What a cleaning schedule is really protecting
A wash is maintenance on the surfaces themselves, not just a cleaning. Paint that is kept free of algae lasts noticeably longer before it needs redoing. Wood that is not held permanently damp by mildew takes years longer to rot. Concrete that is kept clean does not develop the slick biofilm that causes falls.
Measured against the cost of repainting a house, replacing a fence or resurfacing a driveway, an annual wash is a small line item that pushes those larger expenses further out. That is the case for treating it as scheduled maintenance rather than as something you do when the house starts to look bad.
Questions we get on this
On siding, brick, stucco, wood and roofs, it is more effective, because it kills the organism rather than removing only the visible layer. High pressure has its place on concrete flatwork, where the surface can take it and the goal is mechanical removal.
Not with normal precautions. Plants get watered thoroughly before work starts, which dilutes anything that reaches them, and rinsed again afterward. Delicate ornamentals near a wall being washed can also be covered. Tell us about anything you are particularly protective of.
On a soft-washed house, expect a year or more before growth becomes visible again, longer on sunny elevations. Flatwork under trees may show change within months. Where results fade unusually fast, the cause is almost always shade plus a moisture source such as a sprinkler.
