Mold-removing chemical products are good but the mold keeps growing back.

What is an efficient permanent solution?

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  • 5
    That picture is both beautifully fascinating and hideously repulsive at the same time.
    – Kaz Wolfe
    Dec 12, 2014 at 11:53
  • Well first of all I must tell you that this isn't right place to ask this question. Not because it's off topic but because people at home improvement are better at solving this problems. Now, can you give us some details: Here this wall is (ground floor, basement etc.) is it outside wall, is there any plumbing inside (if you know).If it is outside does it have thermal insulation. On which height does the mold appears, is it near floor or near celling? Apr 8, 2015 at 12:31
  • Keeping a room moisture free helps a lot. My other half is an estate agent and her advice is usually to have the heating turned up with the windows open. Not sure why, but it seems to help get rid of the moisture.
    – Terry
    Apr 8, 2015 at 13:28
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    @user1298069 mold is just indicator of some other problem(s).Please give us additional info so we could help you. Apr 9, 2015 at 8:20
  • The mold is in the toilet
    – Flair
    Apr 14, 2015 at 20:44

6 Answers 6


Removing the cause of the problem rather than the problem itself is the only real solution to permanently remove mould .

For mould the usual culprit is moisture. In most cases the moisture will come from one of two places:

  • If the moisture is coming from the air (e.g. a steamy bathroom or a cold hallway) the problem is managed (perhaps not completely fixed) by removing moisture from the air. To remedy this you can try:

    • Use an electric dehumidifier (the little salt block ones simply aren't efficient enough)
    • Keep the area well ventilated, open windows and doors
    • Don't add moisture unnecessarily, e.g. use an extractor fan if cooking or showering generates a lot of steam.
  • If the moisture is coming through the walls, floor or ceiling, the problem is much more difficult and will probably require a professional damp proofing course.

You will also need to remove the mould completely to reduce the chance of spores multiplying again. The chemical sprays you use already are probably enough for this.

  • 1
    I use a bleach spray that is advertised and sold as mould remover. A 10 minute soak, followed by wiping down removes it completely. I do this once a year and it never gets too bad. However, Never paint over it. Once it's trapped within layers of paint like that, it's game over.
    – fredley
    Dec 11, 2014 at 12:50
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    @Tom: I've read in multiple places that bleach isn't that effective vs mold: Just found this page that discusses it: spore-tech.com/viewCategory.asp?idCategory=78 (so "sort of" with a caveat warning .. be careful ;) might work ok on tile, but NOT wood)
    – Ditto
    Apr 10, 2015 at 14:51
  • No, no and no.... Sorry James I don't want to be rude but this isn't good enough answer, but it's really not your fault because OP didn't provide us with enough details. There could be many more things which are causing a mold. My first suspect is that there is no thermal insulation which is causing humidity which leads to mold...we need more details in order to solve this and this is or could be big problem. Apr 12, 2015 at 20:08
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    @pythonstarter, No worries, you certainly weren't rude. As I read your comment however, you seem to mostly agree with my answer. We both identify moisture as a probably factor. Ultimately, my answer is simply: Removing the cause of the problem rather than the problem itself is the only real solution, then I give one possible cause and a possible solution. Apr 13, 2015 at 7:29
  • Yeah,like I said it's not your fault.What wories me is that,since your answer got many up votes OP will take it for granted, and do as you told him.And none of us knows what the problem really is.I agree with your answer,moisture is certanly the cause.Question is where does the moisture come from? Apr 13, 2015 at 19:05

Black mold is caused by Stachybotrys (also known as "toxic black mold" in the US( and it's usually associated with poor indoor air quality that arises after fungal growth on water-damaged building materials and exposure can cause adverse health effects.

The worst-case scenario for homeowners is produced by consecutive episodes of water damage that promote fungal growth and mycotoxin synthesis, followed by drier conditions that facilitate the liberation of spores and hyphal fragments2003.

Remember that simply killing the mold with a biocide is not enough. It can grow on any substance (on wood, paper, carpet, and foods) and there is no practical way to eliminate all mold and mold spores in the indoor environment. The way to control indoor mold growth is to control moisture.

The first step is solving an indoor mold problem which is always stopping the source of moistureEPA:

  • Assess the area infected with mold, checking for any hidden mold.
  • Identify and permanently fix the source of the leaks or seepage (such as water problem) to prevent mold growth. Water leaks in pipes, around tubs and sinks and can provide a place for biological pollutants to grow.

Secondly get rid of mold it-self:

  • Clean and dry any damp or wet building materials and furnishings.
  • Clean mold off hard surfaces with water and detergent, and dry completely.
  • Clean all components of the HVAC system to ensure nothing becomes contaminated.
  • Remove any object/materials near the insulation system that may have been contaminated.
  • Use mold removal compositions (such as containing anionic surfactants and sodium hydroxide)US5783550

After removing mold, here are the things which can prevent mold keeps growing back:

  • Reduce indoor humidity (to 30-60%) to decrease mold growth. Use dehumidifiers and air conditioners (be sure that the appliances themselves don't become sources of biological pollutants).
  • Reduce the potential for condensation on cold surfaces on cold surfaces.
  • Be sure crawlspaces are well-ventilated.
  • Turn off certain appliances (such as humidifiers, kerosene heaters) if you notice moisture on windows and other surfaces. Or remove/dispose contaminated HVAC filter media.
  • Vent your clothes dryer to the outside.
  • Raise the temperature of cold surfaces where moisture condenses.
  • Increase air circulation.
    • Use exhaust fans (e.g. in bathrooms and kitchens) to remove moisture to the outside.
    • Move furniture from wall corners to promote air and heat circulation.
    • Keep open doors between rooms (especially to closets which are colder than other rooms) to increase circulation.
  • In areas where there is a perpetual moisture problem, do not install carpeting. It can absorb moisture and serve as a place for biological pollutants to grow.
  • If you have insulated air ducts and the insulation gets wet or moldy, it should be removed and replaced.
  • Consider replacing the insulation in the HVAC system with an external to prevent future floodwater contamination.

If above conditions causing the mold growth are not corrected, mold growth could recur.

In case where the area of mold is large you should hire a remediation manager to properly dispose of the mold or consult with a qualified professional.

See also:


I have the same problem and I have tried with white vinegar and after several months bleach spray for mold removing (which is not exactly a lifehack but works). The spray works better for me, but smells bad and it is very toxic.

I have made a little research and I found the following strategy:

  1. clean the surface with bleach spray
  2. clean the spray with sponge
  3. dry the surface
  4. apply a special anti-mold basis
  5. paint over it as you add to the paint special chemical against mold (containing some kind of preservatives, anti fungi chemicals, or silver ions)

some cons of this method are:

  • it uses harmful chemicals
  • should not be used if the moisture comes from the wall

If the moisture comes from the wall first you have to make proper isolation.

If the moisture comes from the air then you have to reduce air humidity (ventilation, electric dehumidifier). Find the source of humidity and remove it. Sources of humidity can be household activities such as cooking, washing; big plants; water leakage due to plumbing problem somewhere in the house.


Depending on the environment this is happening in (pets, children, food preparation, ...) this permanent solution might not apply.

A bit of back-ground: Mould is one of the oldest life forms on Earth and thus pretty resistant to pretty much everything... You can temporarily stop growth, but even bleach, ammonia, ... are no permanent solutions.

The solution: Before attempting any of the following remedies, you need rubber boots, chemical gloves and a gas-mask.

Therefore, use the following: (higher number = more effective = more toxic)

  1. Peroxide: The Marilyn Monroe of the solutions, but not the normal pharmacy 2%, but the nasty 30 or 40% industrial-strength product. It works by releasing ionic oxygen, so the gas-mask might seem superfluous but is really needed as it'll burn your lungs. 30-40% Peroxide also stings like hell if even a tiny drop gets on your skin and feels like someone is poking you with a needle for an hour or so (though no permanent damage will be done, happened quite a few times to myself).

    Use a natural sponge (no synthetics!) to scrub off the mould and soak all the tiny cracks the mould is growing out of... You'll notice a slight fizzying as you apply this: this is absolutely normal as the ionic oxygen is being released. Don't just clean the area with the mould itself, but clean as much around it as well as the spores will be everywhere. If possible, clean the walls, floor and ceiling as well in the room/corridor/basement this is happening in. (Don't use a vacuum cleaner: it'll make things worse)

  2. Sulphuric acid: The vitriolic of the solutions, just not the normal battery acid (5%), but real vitriol that is hygroscopic and will not only liquefy any deep spores, but pull out microscopic amounts of water from the cracks that contain the mycelia. No need to describe what vitriol does to your skin: a mummy will look fresh compared to a skin that gets even a tiny drop on it!

    Use a high-quality synthetic sponge and please don't apply this on wood, calcium-containing stone (bluestone, sandstone, calcite), metal or similar materials (bricks, cement, concrete are no problem). You'll notice a bit of heat as you apply the vitriol; this is due to the hygroscopic effect and is absolutely normal. Again: don't just clean the moulded area, but as much around it as well to kill off the spores as with solution #1.

  3. Potassium Cyanide: This is the kill-all of cleaning products! Containing a triple Carbon-Nitrogen bond it breaks open any mould DNA down to the molecular level and leaves behind the most sterile and clean area you've ever witnessed. Just add it to water (even a 2% solution will work great!) and again use a sponge (synthetic or natural: now it doesn't matter) and the same physical treatment as the above solutions. This is the most permanent solution of all!

Whichever of the solutions you took, it's important to let the entire room dry (adding an air conditioner set to dehumidification mode is an asset) as mould needs water (even in microscopic quantities) to flourish!

Final warning: If you would want to apply all of the above, please allow sufficient time between applications as mixing the vitriol with the Potassium Cyanide will generate Hydrogen Cyanide: a gas smelling of nice raw almonds that kills any oxygen-breathing life-form on Earth within seconds!

And finally: apply another coat of water-resistant paint to the surfaces thus treated!

  • 3
    +1! Another great permanent solution is to apply gasoline liberally to the affected area, apply a flame to it, then go get some coffee (it may take a minute). The mold should be gone by the time you return. Sep 29, 2016 at 14:00
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    Thank you @CaptainObvious, but I believe OP would prefer a solution that destroys the mold only, not the entire house. Sep 29, 2016 at 14:04

You have not said where this mould is or what the conditions are. So here is just a helpful guess.

Firstly, the mould spores are always there, you can't get rid of them forever, so you have to stop them from flourishing. Most of all you have to get it dry. Ventilate! Move your furniture and stuff an inch (25 mm) away from the wall. Dry the spot by using heat. Of course this may spread the spores around the place, wash them off first. Make sure your problem areas are always well ventilated. If this is a bedroom then get used to sleeping with an open window.

-Using a dehumidifier is a good short-term solution, but uses a lot of electricity.

-Never ventilate on a warm day when outside is warmer than in. Otherwise warm, moisture-laden air comes in and the water condenses on your cool areas.

That's the first step. Now we have to stop moisture from collecting in corners and similar spots. It does this where one spot is colder than the others. If the house belongs to you then insulate it on the outside. Otherwise talk to your landlord about it. Often cold spots are above window frames because the house structure has design faults. You might like to insulate on the inside, though that's not the optimal solution.

So your answer is to ventilate and insulate.

edit: a new point I thought of. You can paint the problem area with fungus-preventing paint. I got some of this for the north side of my garage and it works very well. However, this is probably not suitable for indoors - but you could ask in the paint shop.


Many mold killing products contain chemicals. These chemicals can be allergenic, bad for the environment, and bad for your family and pets.

Vinegar, on the other hand, is a natural acid. Vinegar is totally non-toxic and safe of course. You can drink it, afterall. Vinegar is also biodegradable and fine for the environment.

Although vinegar leaves a strong smell, the fumes are not harmful at all.

It is very cheap to buy vinegar. You can easily find bottles of white vinegar in the supermarket.

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