Prep first
Before you start
- Fix the water source and dry the wall; spots dry within 24 to 48 hours usually won't grow mold again.
- Put on gloves, goggles without vents and an N-95 respirator before you touch the growth.
- Brush loose mold off outdoors if you can, so the spores don't scatter into the house.
Mold on siding shows up as dark streaks and patches, and it grows wherever moisture stays on the wall. It spreads from tiny spores, so a wash alone may not stop it coming back if the wall keeps staying wet. The material decides how gently you need to work, and on porous building materials mold can fill crevices and may be impossible to remove completely, so an old, deep stain may need replacing rather than more scrubbing.
Test any mold cleaner on a small hidden patch of siding before you work across the whole wall. Small patches of mold on vinyl siding are usually a job you can handle yourself, but large or high growth is worth a pro. Pick a mold and mildew remover made for siding if the usual wash leaves dark streaks behind.
Before you start
What siding, roof & exterior can take
Safe to use2
- Water
- Oxygen bleach
Use with care5
- Soaking
- Chlorine bleach
- Solvents (alcohol, spot removers)
- Acids (vinegar, lemon)
- Scrubbing and abrasives
7 items
What you'll need
Tap an item to get it on Amazon, or tick what you already have.
- Garden hose with a low-pressure spray nozzleRinses the detergent off without forcing water into the siding.
- Soft brushLifts loose growth from vinyl, aluminum and fiber cement without marking the finish. (opens Amazon)
- Stiff synthetic-bristle brushWorks along the grain of painted or stained wood. (opens Amazon)
- Mild liquid detergent and a bucket of warm waterThe base wash for every siding type. (opens Amazon)
- SpongeScrubs the stubborn vinyl spots after the detergent has sat. (opens Amazon)
- Commercial mildew remover labeled safe for painted or stained woodThe wood-safe option for stubborn patches. (opens Amazon)
- Gloves, goggles without vents and an N-95 respiratorKeeps spores off your skin and out of your lungs. (opens Amazon)
As an Amazon Associate we earn from qualifying purchases.
7 steps
Step by step
Step 1 of 7
Identify your siding first
Work out whether the wall is vinyl, aluminum, painted or stained wood, or fiber cement, because each takes a different level of cleaner. If you can't tell, treat it as the most delicate option: a mild detergent and water wash on a small hidden patch. Check that patch after it dries before you clean the rest.
Step 2 of 7
Brush off the loose growth
Knock off the loose mold or mildew with a soft brush before any water touches the wall. Doing it dry keeps spores from scattering into the house.
Step 3 of 7
Wet the wall first
Hose the siding down before any soap goes on, so the detergent spreads evenly and doesn't dry into the surface. Mix a bucket of warm water with a mild detergent, keeping the mix mild rather than strong.
Step 4 of 7
Wash from the bottom up
Work the detergent solution over the siding one section at a time, starting at the bottom and moving up so the runoff doesn't streak the dirty area below. On painted or stained wood, use a stiff synthetic-bristle brush along the grain; on vinyl, aluminum and fiber cement, use a soft brush.
Careful. Don't let the suds dry on the siding.
Step 5 of 7
Rinse with a garden hose
Rinse the dirty, sudsy area off right away with a garden hose on a low-pressure spray, working top to bottom so the runoff stays clean. Keep rinsing until no suds are left on the wall.
Careful. Don't aim a pressure washer at the siding; high pressure can damage fiber cement and its finish, and on vinyl never aim it upward.
Step 6 of 7About 5 minutes
Treat the stubborn spots
On vinyl, moisten the stubborn stains with the detergent and leave it about 5 minutes, then scrub with a sponge and rinse off. On painted or stained wood, a commercial mildew remover labeled safe for painted or stained wood takes the place of the detergent on those patches.
Step 7 of 7
Let the siding dry completely
Let the wall dry fully before you judge the result, then check the same patches again after a few days. If the mold comes back in several days or weeks, repeat the process from the start.
Tip. A quick look after the first wash helps you spot any patch that needs a second pass.
If you'd rather buy than mix
Best products for mold on siding, roof & exterior
For wood siding, test the mild detergent wash on a hidden patch first. For vinyl and aluminum, a mild liquid detergent is all the wash needs.
Dawn Ultra Dish Soap Refill Jug
These are the everyday supplies the steps above use, in the versions most people buy on Amazon.
Finished the steps? How does it look?
Nice work. Let it dry completely and check it again in good light. Here is what done looks like:
How to tell it's really gone →A faint mark usually needs one more round, not a stronger product.
See what to do for what you're seeing →Heavy buildup usually takes more than one round.
Heavy or long-standing buildup →When to call a professional →How to tell it's working
Once the siding is dry, the washed area should look even, with no dark fuzz or spotted patches left. If a patch still looks dark, go back over it with the stubborn-spot treatment rather than scrubbing harder, and give it a few days before you decide it has stayed.
What changes for yours
Adjust for your siding, roof & exterior
House walls and painted exterior siding
Painted walls and painted siding take the same wash, but the paint is what you protect. Fiber cement with a painted finish needs the gentlest approach: no bleach, no acid, no hard metal brush and no abrasive sponge.
Test a corner of the paint first, and if it starts to lift or dull, stop and let the wall dry before going further. Painted siding is a good reason to skip hard scrubbing altogether.
Vinyl siding
Vinyl is the most forgiving of these, but it has its own limits. Stay away from organic-solvent cleaners, undiluted bleach, liquid grease remover, nail polish remover and furniture polish, since they can damage the panels.
If a stubborn patch is still there after one moisten-and-scrub pass, repeat that pass rather than scrubbing harder. Vinyl that has been cleaned well should look even, with no dark fuzz left behind.
Heavy or long-standing buildup
Old mold that has been on the wall a long time can be harder to lift, and it often shows as dark staining more than fuzz. Mold can fill crevices in porous building materials and be difficult or impossible to remove completely, so replacing the piece may be the realistic answer.
Dried mold on wood siding often needs a second pass. Put the mild detergent solution on the wood and keep it wet for about 15 minutes, misting it with a garden hose if it starts to dry, then rinse thoroughly.
If the stain is still there after that, repeat the process rather than scrubbing harder, because aggressive scrubbing and caustic cleaners can wear away the wood surface. Mold that keeps returning usually means moisture is still reaching the siding, so fix that as well.
Vinegar, baking soda, peroxide and more
Do home remedies work on mold on siding, roof & exterior?
Most home remedies for mold were written for fabric or indoor hard surfaces, so they don't carry over neatly to siding. To clean without damaging paint or scrubbing hard, let the mild detergent do the work: wet the wall, wash, leave stubborn patches about 5 minutes, and rinse. Only mild detergent and a low-pressure rinse suit siding, so the rest are skipped.
Helps1Skip5
What makes it worse
Mistakes to avoid
Don't mix bleach with ammonia
Never mix chlorine bleach with ammonia or any cleaner containing it, because the mix produces toxic fumes. Check the label of any cleaner you pick up before you use it on the house.
Don't rely on bleach as a routine cleaner
Chlorine bleach and similar biocides aren't recommended as everyday mold treatment on siding. If you do use one, ventilate and exhaust the air outdoors.
Don't paint or caulk over mold
Paint or caulk laid over mold is likely to peel, so clean the surface and let it dry first. Only paint once the wall is clean and fully dry.
Don't run the heating or cooling system if it is contaminated
If you suspect the heating or cooling system has mold in it, don't run it, because it can spread mold through the building. Have it checked before you turn it back on.
Don't scrub wood siding with steel wool or wire brushes
Leftover iron in steel wool or wire brushes reacts with the wood's natural extractives and leaves stains. A synthetic-bristle brush avoids that problem.
Troubleshooting
If the stain is still there
Pick what you're seeing:
Streaks appear after washing.
Solution dried on the wall or dirty runoff ran over dry siding. Re-wet the area and wash again from the bottom up, rinsing each section immediately.
Dark marks remain on wood siding after cleaning.
Try a commercial mildew remover labeled safe for painted or stained wood. If marks remain, they may be staining or damage rather than active mold.
Water is getting behind vinyl panels.
Stop spraying upward. Hold the hose or wand level or angled down so water runs off the panels, not under them.
When to call a professional
Sewage or contaminated-water mold is a job for an experienced professional, not a wash-and-rinse job. For bigger areas, follow established remediation guidance or bring in a professional before you start.
Questions
Is black mold on siding handled differently?
No, black mold on siding is cleaned the same way as any other mold, so the same detergent wash applies with no special product. Wear gloves, goggles without vents and an N-95 respirator while you work, and bring in a professional if the growth covers a large area.
Can you remove mold from a house yourself?
Yes, for small patches of surface mold, roughly 10 square feet or less. Anything bigger should be handled under established remediation guidance or by an experienced professional.
What cleaner should you use on mold on house siding?
Mild detergent and water covers vinyl and aluminum, and a commercial mildew remover labeled safe for painted or stained wood suits painted or stained wood. Fiber cement stays with the mild wash.
Will mold come back on siding after cleaning?
It can, because mold only grows where moisture keeps reaching it. Fix the source of the wet spot, and repeat the wash if the mold returns in several days or weeks.
Does mold permanently damage siding?
It can. Mold can leave staining and cosmetic damage that doesn't always come out, so a mark that stays after a proper cleaning may be the surface itself.
How fast does siding need to dry to avoid mold?
Wet areas that dry within 24 to 48 hours usually won't grow mold, so aim to get the siding dry inside that window. If it stays damp longer than that, expect growth to return.
Is vinegar a good mold cleaner for siding?
Not for siding. Vinegar is meant for light mildew on hard indoor surfaces, so the mild detergent wash is the better choice outside.
Mold on other materials
Other stains on siding, roof & exterior
Start from the bigger picture
How we know this
Every method, amount and warning here comes from university extension services, industry bodies and product makers. We read them, check every step for unsafe combinations and changed amounts, and write it up so you can follow it.