First few minutes
Just happened? Do this first
- Deal with epoxy before it cures, using paper towels.
- On skin, use a waterless skin cleanser for resin, then wash with soap and warm water. Never use solvents.
- Change any clothes that epoxy has spilled on right away.
- If epoxy or wet foam gets in your eyes, flush them with water for 15 minutes and get medical help if discomfort lasts.
Epoxy and spray foam on siding are much easier to handle while they're wet, since cured foam has to be scraped off rather than rinsed away. Once epoxy has set, what's left is residue, and the goal is to loosen it without harming the siding or the paint on it. Test every cleaner on a hidden patch first before going over the whole wall.
For leftover residue, an adhesive remover is the usual choice, and oxygen bleach powder suits any staining it leaves behind. Fiber cement and painted wood react differently, so check which siding you have before you pick a product. If the paint starts to lift or vinyl looks dull after a few passes, stop and call a pro.
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
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- Paper towelsThey wipe up wet epoxy and excess resin before it cures. (opens Amazon)
- Plastic drop clothIt protects nearby plants from overspray. (opens Amazon)
- Garden hoseIt rinses the siding before and after washing.
- Mild dish detergentIt's the washing agent, mixed in water. (opens Amazon)
- Soft brush or clothIt cleans siding and fiber cement without damaging the finish. (opens Amazon)
- Oxygen-bleach cleanerIt treats mildew or organic growth on wood. (opens Amazon)
- Stiff synthetic-bristle brushIt scrubs wood along the grain. (opens Amazon)
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6 steps
Step by step
Step 1 of 6
Wipe up wet epoxy first
Deal with any wet epoxy before it cures, since paper towels are the right tool for spills and excess resin. Once it has hardened, the rest of these steps are the realistic route.
Tip. Work from the edge of the spill inward so you don't spread it.
Step 2 of 6
Clear debris and protect plants
Sweep away leaves and debris from the siding before anything gets wet. Cover nearby plants with a plastic drop cloth, and spray them with water to dilute any overspray.
Step 3 of 6
Test every cleaner first
Choose an inconspicuous area and test the cleaner you plan to use there, along with any pressure washer setting. Wait to see how the siding looks before you work across the whole wall.
Careful. On vinyl siding, never aim a pressure washer upward.
Step 4 of 6
Wash gently with dish detergent
Rinse the siding with a garden hose first, then scrub with mild dish detergent in water and a soft brush. On fiber cement, use a soft brush or cloth, and keep your scrubbing light at every spot.
Careful. A hard metal brush or abrasive sponge can damage the finish on fiber cement.
Step 5 of 6About 15 minutes
Treat mildew with oxygen bleach
On wood, apply an oxygen-bleach cleaner to the mildew or organic growth, working in sections. Keep it wet for the dwell time on its label, about 15 minutes, then scrub along the grain.
Tip. Mist the area with the hose if the cleaner starts to dry before the time is up.
Careful. Never mix bleach with ammonia or a detergent containing ammonia, since it forms a toxic gas.
Step 6 of 6
Rinse everything away completely
Rinse thoroughly with a garden hose until no cleaner, suds or residue are left on the siding. Work section by section so nothing has time to dry on the surface before you reach it.
Careful. Don't let cleaners or soap dry on the siding.
If you'd rather buy than mix
Best products for epoxy on siding, roof & exterior
Pick an oxygen-bleach cleaner made for wood, and read its label for the dwell time before you start.
Amazon Basics Microfiber Cleaning Cloths
How we picked these: each product is made for this type of stain, its maker doesn't warn against using it on siding, roof & exterior, and its directions fit the steps above.
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.
If the stain was already dried or set, the method changes.
Old, dried or set-in stains →When to call a professional →How to tell it's working
The siding should look even, with no sticky film or dull patch left over the spot. On wood, the grain should look clean and the surface shouldn't feel slick or soapy after the rinse.
What changes for yours
Adjust for your siding, roof & exterior
Vinyl siding
Vinyl gets the same first steps: wipe up wet epoxy, test the cleaner, then wash with mild dish detergent and a soft brush. What changes is what stays off it, since organic-solvent cleaners, liquid grease remover, nail polish remover and furniture polish can all damage the surface.
Undiluted chlorine bleach is also off the list, so stick to the mild wash and a thorough rinse.
Fiber cement siding
Fiber cement takes a soft brush or cloth for washing, and the scrubbing should stay gentle at every spot. For mildew on this siding, use a mildew-specific cleaner with a soft cloth rather than the oxygen-bleach cleaner used on wood.
Leave out the wood brightener, since acid isn't for fiber cement, and keep the washing to a hose and a soft tool.
Painted or weathered wood siding
Wood siding follows the oxygen-bleach step, with the scrub going along the grain and a rinse afterward. If the wood has grayed, a commercial deck cleaner or brightener can remove the mildew and dirt so the wood's own color shows.
If all the natural color has leached out, the wood stays silver when dry, and those fibers should be left alone rather than scrubbed back to new.
Spray foam on siding
Cured spray foam can't be dissolved, so the washing steps won't lift it. It has to be scraped off the siding instead.
Spray foam is a flammable aerosol, so shut off pilot lights and other ignition sources while you're using it. Don't keep soaking cured foam in solvent, because once it has dried, it won't come off that way.
Old, dried or set-in stains
Old epoxy that has cured on siding may never come off, and cleaners won't change that. Once it has dried, spray foam can't be removed with any solvents or cleansers, so it has to be scraped off the surface.
For old grime on wood, a commercial deck cleaner, brightener or restorer removes mildew and dirt, and you can scrub along the grain with a stiff synthetic-bristle brush. If the wood's natural color has leached out, it will stay silver when dry, and those fibers should be left in place.
Old stain or sealer comes off with a stain and sealer remover, which you neutralize with a brightener and then lightly sand once dry. Tannin bleed and rust streaks on wood respond to an oxalic-acid brightener, used per its label, but that stays off fiber cement. Realistically, the wood will look cleaner and brighter, but the epoxy itself may still be there, so contact a hardware store about the leftovers.
Vinegar, baking soda, peroxide and more
Do home remedies work on epoxy on siding, roof & exterior?
A garden hose, mild dish detergent and an oxygen-bleach cleaner for mildew handle siding better than most household remedies. Most other household remedies are better skipped on siding.
Works2Skip4
What makes it worse
Mistakes to avoid
Don't pressure wash fiber cement siding.
A high-pressure power washer can damage the surface and finish on fiber cement, so a hose and soft brush are the right tools there. Save the pressure washer for wood, using the lowest pressure that cleans, a fan tip and spray along the grain.
Don't power wash soft woods like western redcedar.
Pressure removes wood from the surface of soft species like western redcedar. Scrub gently by hand and rinse with a hose instead.
Don't use steel wool or wire brushes on wood.
Leftover iron in the metal reacts with the wood's natural extractives and leaves stains. Use a stiff synthetic-bristle brush along the grain instead.
When to call a professional
Call a professional if you're unsure about pressure washing, since siding can be damaged in the wrong hands. If the wood is old treated lumber, replace it rather than cutting or burning it, because the sawdust and smoke contain arsenic.
Questions
Can epoxy be removed from siding once it cures?
Usually not completely. Cured epoxy may not come off siding at all, so remove what you can and contact a hardware store about the rest. The best result always comes from wiping up the wet spill before it sets.
How do I get spray foam off siding?
Cured spray foam can't be dissolved by solvents or cleansers, so it has to be scraped off the surface. Wet foam is much easier, so wipe it quickly with a cloth without spreading it.
Can I pressure wash epoxy off siding?
Only on wood or vinyl, and only with care. Use the lowest pressure that cleans, and never on fiber cement.
Is chlorine bleach safe on siding?
Opinions differ on chlorine bleach for siding, so it's safer to skip it. An oxygen-bleach cleaner handles mildew on wood without that risk.
What should I use on black spots on siding?
Treat them as mildew or organic growth on wood, using the oxygen-bleach cleaner kept wet for about 15 minutes. On fiber cement, use a mildew-specific cleaner with a soft cloth instead.
Can I brighten grayed wood siding?
Yes, a commercial deck cleaner, brightener or restorer can remove mildew and dirt so the wood's own color shows. If all the natural color has leached out, the wood stays silver when dry and should be left alone.
Epoxy 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.