Paint sticks to whatever is on the wall. If that is mildew, chalk, and pollen, the new coat fails along with them. Here is what the prep wash has to remove, how long the siding needs to dry, and how a painter can hand the wash to someone else.
New paint does not bond to siding. It bonds to whatever is on the surface of the siding. If that surface is a film of mildew, a layer of chalk, or a season of pollen and road dust, the paint is stuck to something that is itself barely stuck to the wall. It looks fine for a few months. Then it peels, usually on the shaded side first.
Mildew is the worse of the two because it is alive. Paint over live mildew and the spores keep growing underneath, then show back through the new color as gray or black specks. Paint labels almost always call for a clean, dry, sound surface, with mildew and chalk removed. The prep wash is how you get there.
That is why good painters do not open a can until the house has been washed. Some do the wash themselves. Plenty in this area hire it out, because a wash crew with the right equipment does it faster and the paint crew can stay on another job.
The green and black growth on shaded walls, under eaves, and behind shrubs. It has to be killed with a cleaner, then rinsed. Rinsing alone leaves live spores behind.
The powder that comes off on your hand from old paint, vinyl, and aluminum. A light layer washes off. A heavy layer needs a cleaner made for it and often a brush.
The gray layer on every wall, thicker near driveways and roads. Spring pine pollen adds a yellow coat that paint will not bond through.
Under soffits, around light fixtures, and in porch corners. Paint over a mud dauber nest and the paint falls off with the nest.
Around range hood and dryer vents, and on the wall beside the grill. Paint will not hold on grease, so these spots get a degreaser.
Rust lines under fixtures and gutter straps, and tannin bleed on some woods. These may need spot treatment, or a stain-blocking primer the painter chooses.
What the wash should not do is strip paint. Loose and peeling paint comes off by scraping and sanding, done by the painter, with a method chosen for the age of the house. More on that below.
Chalking is what paint, vinyl, and aluminum do as sunlight breaks the surface down. Rub your palm or a dark cloth across a sunny wall. A little white is normal on older paint. A heavy, even coat of powder means the surface is chalked through, and paint applied over it will be held on by powder.
Light chalk comes off in a good wash. Heavy chalk is a different job. On vinyl and aluminum it often calls for a dedicated cleaner and brush work, which is what we do as oxidation removal. Our guides to chalky vinyl siding and aluminum siding oxidation explain how to tell how far it has gone.
After the wash, once the wall is dry, test again. If your hand still comes away white, the painter needs to know before priming, and the paint label will say what that surface requires.
A simple test many painters use: press a strip of clear tape onto the washed, dry wall and pull it off. If the tape comes away white, the chalk is still there.
There is a quick way to tell mildew from dirt. Put a drop of household bleach on a dark spot. If it lightens within a minute or two, it is mildew. If it does not, it is dirt.
The prep wash uses a cleaner that kills the growth where it sits, gives it time to work, and then rinses it off at low pressure. It is the same soft wash we use on any house, with extra attention on the places that grow mildew fastest: the north side, porch ceilings, the wall behind shrubs, and the bottom few feet where splash keeps the siding damp. The guide to the green north wall explains why those spots always go first.
Rinsing matters as much as killing. Cleaning solution left on the wall can get in the way of adhesion, so a thorough rinse of every wall, window, and trim board is part of the job, not an extra.
A prep wash is not a stripping job. High pressure drives water behind vinyl laps and into the end grain of wood siding and trim, and wood that has soaked up water takes far longer to dry. On wood it can also raise the grain and leave fuzzy, furred patches that paint does not cover well.
Low pressure with the right cleaner removes everything that should come off. Paint that comes off in a soft wash was going to fail anyway, and the painter will scrape it. Paint that only comes off under high pressure was holding, and blasting it away just adds sanding and priming to the painter's list.
This is the question every homeowner asks, and the honest answer depends on the wall. The paint manufacturer's label is the authority. It states the conditions the surface and the air need to meet, and the painter should follow it over any rule of thumb, including ours.
As general guidance, here is how drying usually goes in this area:
| Surface | General drying guidance | What slows it down |
|---|---|---|
| Vinyl siding | Usually ready after a full day of dry weather | Water trapped behind laps, shaded walls, high humidity |
| Fiber cement | Often a day or two | Cut edges and butt joints hold water longer than the face |
| Painted wood siding and trim | Often two days or more, best confirmed with a moisture meter | End grain, shade, and any wood that soaked up water |
| Brick and stucco | Often several days | Masonry holds water deep and dries slowly through the face |
| Any surface after a rain | Start the count again | A rain after the wash resets the clock |
North Carolina humidity stretches every one of those. A wall in full sun in October dries far faster than a shaded wall in a sticky July. Dew matters too, because paint applied late in the day can still be wet when the dew falls. A painter with a moisture meter on wood siding is working from a reading, not a guess, and that is the right way to make the call.
If the house was built before 1978, the paint on it may contain lead. Intact paint is not the main hazard. Disturbing it is. Scraping, sanding, or blasting loose paint off the wall puts lead chips and dust into the soil and the air around the house, where children and pets find it.
Federal and state rules govern how paint is disturbed in pre-1978 homes when the work is done for pay, including how debris is contained and who has to be certified to do it. Those rules apply to painters and to other contractors. So test first. A lead test kit or a certified inspector will tell you what is on the wall before anyone decides how to prepare it.
Order matters across the whole property. If the roof needs a roof wash, do it before the siding, because it runs down the walls. Gutters before walls. Concrete last, after the painting is finished and any drips have dried.
If you would rather keep your crew painting, the prep wash is easy to hand off. You sell the paint job. We wash the house before your crew arrives, on a date that leaves time to dry, and you get photos of every elevation when we finish. We do not paint and we do not quote paint work, so there is never a question about whose customer it is.
Photos of each elevation help us price it without a visit. Tell us anything we should know: lead test results, loose paint, areas you plan to scrape, and plants the homeowner cares about.
We schedule it with enough lead time for the surfaces to dry before you start. Weather moves both of us, so if rain pushes the date, you hear it from us that morning.
Soft wash on every elevation, soffits and porch ceilings included, a full rinse of glass and trim, and dated photos you can show the homeowner.
Rub test, tape test, moisture meter on the wood. If something is not right, we come back and make it right. That policy covers work we do for a painter the same as for a homeowner.
We are licensed and insured, and we send a certificate of insurance before the first job. We take prep washes for painters in Clayton, Garner, Raleigh, Smithfield, Cary, and the rest of the Triangle.
If you are about to repaint, book the wash for the week or so before the painter starts, not the day before. Ask the painter how much dry time they want and whether they want to walk the wall after the wash. If the painter's bid already includes a wash, ask how they do it: what cleaner, what pressure, and how long they wait before painting. Rinsing the house with a pressure washer the morning the priming starts skips most of what makes paint last.
If you are not ready to repaint and the house just looks tired, wash it first and look again. A lot of siding that reads as faded is only dirty, and a wash can put off a paint job for a few more years. Call (919) 698-3669 and we will tell you which one you have.
We do this work every week across the Triangle and Johnston County. Free quote, no obligation, and a real person on the phone.
“They brought the color back on our vinyl siding after another company left it chalky. Night and day.”
“They transformed the outside of our house. The siding looks brand new and they were careful around all my flower beds.”
“Came out on a weekend when I needed it and the results were excellent. Real person answered the phone every time.”
Low pressure and non-pressure roof cleaning are the same idea: the solution does the cleaning and the water only carries it away. Here is what that looks like on shingles, metal, and flat roofs, and how long it holds in central North Carolina.
Read the guide →ConcreteA driveway clean is more than a pressure washer and an afternoon. Here is what a proper concrete cleaning service does, stain by stain, and what no amount of cleaning will fix.
Read the guide →ConcreteA patio is not one surface. Broom-finish concrete, stamped concrete, pavers, flagstone, and brick all clean differently, and the method that suits one of them can ruin another.
Read the guide →We fly the roofline and show you the footage on the spot. You see your own gutters, joints, and downspouts on the screen instead of taking our word for it. It costs nothing and you are not committing to the cleaning.
Free for homes and businesses across the Triangle and Johnston County. No obligation to book any work afterwards.
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