Back in the day I've heard that bleach is a good way to kill mold. The other day a home inspector suggested that Dawn dish soap actually works much better than bleach. I've heard from another home inspector to use the store-bought mold killer.

Does anyone know what really works and what doesn't for a DIYer?

  • 4
    Both bleach and detergent can kill surface mold.
    – DA01
    Jun 3, 2012 at 17:57
  • Bleach will react and become inert after a short period of time and the mold can re-establish. Detergent will stick around a lot longer. Other mold treatments include Sodium Carbonate, TSP, and other salts that make it hard for mold to re-establish especially if things are kept relatively dry.
    – Paul
    May 2, 2015 at 13:35
  • 1
    Yes an home inspector said to clean with dawn then spray with bleach.
    – user47886
    Jan 16, 2016 at 16:00

10 Answers 10


I just find it useful to recap all the information I could find on the web about it and the unanswered questions and hypotheses that still need to be tested. Please feel free to correct and update my answer or by commenting below (Verified information and test result are more than welcome). This answer is a work in process: many things written here need confirmation (and others would require answers from the stack chemistry)

In brief: our current technological level isn’t advanced enough to solve that issue... The solutions proposed below are just a workaround. As mold needs moisture + cellulose (it eats it) + air to survive, the most efficient way remains either to control humidity (which is unfortunate for those who can’t do it), or (easier and cheaper) to simply wrap the things the mold love to be (e.g. wood, or the cellulose of a plasterboard) with a hermetic substance (you'll find below a super cheap DIY solution).

Molds are difficult to eradicate because:

  • It can live deeply inside stuff. So only killing the visible mold isn’t enough.

  • Killing all the mold (the visible ones and the one deeply rooted in stuff) isn’t enough as the molds generate countless tiny spores (their “seeds”). A single spore can start by itself a whole new mold invasion. And their spores are really tough (1) and they also float in the air.

So to get rid of mold invasion, several actions seem to be required:

  • 1/ killing the visible mold,
  • 2/ killing the molds deeply rooted inside the wood, wallpaper…
  • 3/ preventing the next invasion by:
    • making the environment harsh for the molds to grow
    • deactivating/killing the spores

Killing the visible mold is easy: just use bleach or peroxide … (cf the below). But it could come back in a day or two...

Killing the molds deeply rooted is another story as you need something to help the product (which kills the molds) penetrates inside the wood. You need to use a “surfactant”, like dishwashing soap (or a better one, which one?) (1). (I never worked for me).

The easiest, cheapest way, and often the only solution (if you can't lower the humidity): use a hermetic coating

There is a DIY super cheap solution: by mixing 10gr of polyurethan foam with 80gr of acetone you can waterproof stuff with this water-like substance. But it only works if you put several layers (at least 3). A single layer isn't hydrophilic nor waterproof, but ‘breathable’. If I remember well, each layer is pierced by some tiny bubbles and thus tiny holes. So, the more layers you add, the more waterproof (but also rigid) it becomes. With this cheap stuff I waterproof my camping gears, and humid walls. Molds can't pass through several layers. (But be careful: acetone can dissolve / destroy many stuffs like some type of plastic).If needed put a layer of paint over it at least to protect it from UV, and because, if you take the cheapest foam, it'll be UV sensitive, the coating will turn yellow, then brown after a few weeks/months (which can be quite nice).

BONUS: you can reuse the spray can for month by using this trick:

⚠ WARNING: be very careful to not touch the mix of acetone and polyurethan foam, not even with gloves as it contains isocyanates (present in the hardener or catalyst of polyurethane-based two-part paints. It will be dissolved by acetone and will easily penetrate your skin and most gloves ― I recommend applying it using a paint roller or, if you really need to touch it, using Butyl gloves, or (cheaper) 2 layers of latex gloves under some DIY gloves made out of PP plastic bags ― latex gloves will only protect you for few minutes, maybe even seconds).

other information (theorical)

UVC lamp could (theoretically) kill and prevent the invasion

They work in 2 ways:

  1. they destroy (some) mold with ultraviolet radiation (and their spores, which is very hard to do)
  2. they also destroy them with the ozone gas they are producing.

Obviously, you have to be very careful since these lamps a very dangerous for every form of life (including you). It can cause cancer, blindness... Even half a second on your eyes/skin is too much. You should simply light the lamps when you are out or wear adequate protection if you don't mind breathing ozone gas (some UVC lamps don't produce ozone though). Plastics don't like it either (eg. you monitor, laptop...) but UVC photons aren't really strong: a simple thin sheet of plastic (even transparent) might be enough to stop them (they don't pass through a transparent glass either). But don't trust me, check it yourself.

I would first clean it with bleach (or peroxide), then use a powerful UVC lamp (maybe x(?) hours per week when the moisture is high). (That should do the job until the new generation of dehumidifier/desiccant like MOF will come to the market (currently desiccant dehumidifier like this seem to be the best). Or better: an RNA treatment to either destroy them or to stop them being toxic, or even a GMO healthy fungus that would fight the unhealthy one while providing some cool benefits (green light on the dark, nice sm?). Can't wait for the future...).

How to (try to) prevent further invasions?

—By making the environment harsh for the molds to grow: molds seem to be sensitive to pH. Some molds will be destroyed by an acid pH, but (most) others will be destroyed by very high/basic pH (over 9).

—By deactivating/killing the spores: that’s the tough part.

Borax (Sodium borate, sodium tetraborate, or disodium tetraborate) has a quite basic pH (but less than bleach), so , in theory, (it didn't work for me) it should Kills/prevent or slow mold growth. Once again, most, but not all types of molds need an acidic environment.

1 tablespoon in warm water (about 40 °C—makes it easier to dissolve it). According to many sources, Borax was effective and durable but some concerns have been raised about its effect on health (especially when ingested or when in contact with eyes). If I understood well, it was widely used for everything and anything without any concern about its potential toxicity (it’s also not biodegradable). So in results, it has been “classified” by the European Commission as a potential threat (fertility issue, among others). As borax becomes difficult to find (in the EU) I was wondering if any strong basic solution could do the job. What about for instance a solution containing (cheap) dishwasher powder (2)? “Borax Substitute”: sodium sesquicarbonate is much easier to find (in the EU) than Borax but is it really as efficient? And what about its durability (unlike borax, it’s biodegradable) (2)?


—Concrobium Mold Control: this product also plays on the pH to remove molds. It contains sodium bicarbonate (baking soda, pH=9), sodium carbonate (washing soda, pH=12), and trisodium phosphate (TSP, pH=12). Is TSP use only to increase the pH or for other reasons (2)?

—Sodium Bicarbonate: its pH is lower than Borax so it seems to be less effective (in my case, this solution did slow a bit the process, but not much). But it’s safe.

—Sodium percarbonate: (2) —Trisodium phosphate (TSP): (called “borax substitute”). Does it work despite its biodegradability? (2)

—The sealing solution (seems to be the most effective with the UVC): Clean up the mold from the support, wait long enough to dry it, and then “vitrify” the support (using for instance any transparent basic flooring product). The mold won’t come back on it since a thin layer of “plastic” protect its food (cellulose) against it. As for the mold that has been sealed under the layer, it’s not clear what will happen. What would happen to a mold simply recovered with a thin layer of PU or wax? But it will protect from the spores which are the main health issue. (2)?

How to Kill the Mold?

  • Bleach: kill the visible mold (how? (2)), but the chlorine doesn’t penetrate into the wood, wallpaper, so it doesn’t kill the molds deeply rooted. The water contained in the bleach will penetrate the wood so that will help the ‘inside’ molds to grow faster.

  • Hydrogen peroxide: same as bleach, but safer (no toxic gas)

By changing the pH:
Acidic solution (Vinegar…): might kill the mold that needs basic pH.
Basic solution (baking soda, borax…) might kill molds that need acid pH.

You can try to remove the mold with a sponge mix (cold) water and bleach (50% each) to kill the visible part. Then to dissolve anything basic (like borax, if you don't want to have kids) and some dishwashing soap. Wear a mask to protect yourself from the spores.

How to Kill/deactivate the spores:

Since spores can float in the air, some people recommend using Chlorine Dioxide: it’s a gas that kills (deactivates) the spores (of most species). But... the gas is unstable and explosive from a certain concentration, so you won’t find it in your supermarket. But it’s "easy" to make ("providing you find sodium chlorite"… I didn't). You only need to mix a drop of sodium chlorite with a drop from any acid (e.i: citric acid). When the two drops meet, the gas is produced. It’s best to evacuate the building during the process (they recommend 48h). (You can find on eBay devices measuring the concentration of this gas.) Some hospitals use this technic to disinfect. (UVC/ozone lamps seem easier, safer).

In brief, many questions remain. We are still waiting for the scientific invention that will deal with that (a smart virus maybe?). Meanwhile, MOFs based dehumidifier/desiccant should be soon available. I recommend putting a hermetic layer 1) to protect yourself from the toxicity of the mold and 2) to protect the thing it's growing into from humidity. (Cf. my super cheap solution above).





Using UVC: https://www.epa.gov/indoor-air-quality-iaq/does-ultraviolet-uv-radiation-uv-lamps-kill-mold-0

  • spent quite some time to share these info, to get down-voted. Why?
    – JinSnow
    Jan 13, 2017 at 15:44
  • 1
    Not the downvoter, but length of time spent on answer does not directly correlate with quality of answer
    – Tom Busby
    Mar 6, 2017 at 11:09
  • @TomBusby I agree. But concerning the down-vote you justified by your comment, I would say it reflects the average stack user's way to use the downvote button.
    – JinSnow
    Mar 6, 2017 at 12:05
  • @JinSnow, stumbled across your post a year later. I suspect the downvote was for this reason. Answers are intended to be definitive solutions. You've got a lot of information here, but it mostly duplicates other answers and much of the supplemental information is worded as speculative, even adding new questions. You added some general reading sources at the end, but not tied to specific facts. It might have received a better reception if you had limited it to just what you know for sure (citations), and left off your own unanswered questions and anything speculative.
    – fixer1234
    Feb 4, 2018 at 23:55
  • 3
    @TomBusby "Answers are intended to be definitive solutions", no. Answer are intended to bring the most useful information. In most case there is no permanent answer, solutions are constantly evolving. "Not tied to specific facts", well, only "known alternative to get rid of mold". Some people join stack to rule it and impose their views, others to share information. You'd better invest your time in proposing better answer than downvoting/wasting time of people who invest their time to share.
    – JinSnow
    Feb 6, 2018 at 8:45

Bleach, when used carefully, may be effective at killing surface mold. However, when I started to research how to get invisible to the eye mold and it's related odor out of some unfinished wood, over and over I kept finding assertions that bleach is inadequate for eliminating mold issues for the following reason:

Mold's hypae (root structures) actually grow into wood and drywall like roots. The hyphae are not killed by bleach because bleach's ion structure prevents chlorine from penetrating into porous materials such as drywall and wood. It stays on the outside surface, whereas mold has protected enzyme roots growing inside the porous construction materials. When you spray porous surface molds with bleach, the water part of the solution soaks into the wood while the bleach chemical sits atop the surface, gasses off, and thus only partially kills the surface layer of mold while the water penetration of the building materials foster further mildew and mold growth. [This quotation appears on many websites almost word for word, but no site I looked at gave any credit to the original source of this information]

How do you get those hyphae out of the wood or other material? You need a surfactants.

Surfactants serve the purpose of significantly lowering the surface tension of water to allow a cleaning solution to penetrate porous surfaces -KleanPros

What's an example of a Surfactant? Dishwashing soap.

This is why some mold cleaning guides will suggest adding dishwashing soap into your bleach/water mixture, or say to skip the bleach entirely, and just use the surfactant cleaning properties to dislodge the mold and remove it from the surface without actually "killing" it.

A mold expert who came to do mold testing at our home claimed that, depending on the species of mold being eradicated, that bleach was the "worst thing you could do" in fixing a mold problem, because it may cause a release of highly toxic mycotoxin particles. Neither the EPA or OSHA recommend bleach for mold removal under "most" circumstances.

The EPA also points out that:

Dead mold may still cause allergic reactions in some people, so it is not enough to simply kill the mold, it must also be removed.

Which goes back to that surfactant thing. If you're talking about a non-porous surface, sure, bleach may work well, so long as you use it properly (ventilate, don't mix with ammonia, etc), but if there's any possibly porous or crevice-filled surfaces, either the dish soap or a epa-registered mold-killing product would be a reasonable choice.

  • 2
    Basically it's always been a three step clean down process. Bleach on the first pass to kill and remove the surface equivalent of mushrooms, rinse with damp towel passes and then take the remainder down with soap solution which you only rinse off later if you're painting. It has to soak into the myceliar component of the fungal growth. Then when you paint, there are anti-mold additives to mix into the paint. And the first pass had better be done as you point out, after educating yourself on what you have. Libraries have some nasty stuff that grows on leather, you don't want to breath it. Feb 2, 2014 at 0:49
  • Dispensing with the bleach isn't a bad idea, chlorine isn't something you should be breathing. Feb 2, 2014 at 0:51
  • 2
    Be cautious what dishwashing soap you mix with bleach. Some combinations create a chemical reaction that produces toxic vapors. The dishwashing soap should have a statement somewhere on the back label indicating not to mix with bleach, if it is an issue. I usually google to double check even if I don't see it labelled.
    – AaronLS
    Oct 31, 2017 at 2:16

I've personally found that a spray bottle with a 20% bleach-80% water worked best.


So I’ve been in the remediation industry for almost 15 years and yes everyone has their opinions so what the hell I’ll add mine. Bleach does not completely kill mold it more so stabilizes it. And that’s a short answer. As for dawn dish soap I have used it on mold remediation jobs for cleaning and disinfecting. Every time I did never failed an air test. That was about 10 years ago as well Lowe’s and hope depot have products that are way more suitable for a mold remediation these days. There are many different ways to rid the mycrotoxins out of your home here are my recommendations

Rmr Fog with benefactor Benefactor Iaq 6000 Simple green lol Any disinfectant that will completely kill spore plus nucleus's

  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know how best to contribute here. Oct 10, 2019 at 11:24

Hydrogen peroxide and water are what I use. A 3% peroxide and water is what they used at a hospital I worked at. They told me that hydrogen peroxide was one of the safest sanitizers there was with no residue or smell like bleach has. Reading the other answers a surfactant may be helpful but I would probably use jet dry (first have to find out if it would be safe to mix with hydrogen peroxide) the jet dry would not leave a residue like dish soap would. Jet dry is the stuff you add to your dishwasher to reduce spots. With proper humidity levels I have sprayed unfinished wood it killed the mold and never came back after sealing the floor and adding a dehumidifier in a partly finished basement.


Tea tree oil . Mold cannot thrive in its presence. Oil of oregano is even better. I can't attest to how much it kills, or what happens to the mycotoxins, I'm sorry. I have read that oil of clove is effective for stachybotrys control. I don't know how much or what type of clove. I do use it if I am out of oregano oil but I'm not sure what it does. I'd rather use that than use nothing. I did want to share my small input here because having a spray bottle with 30 drops of oregano oil to a half a cup of water to spray into the air or onto a surface has enhanced my life after having been exposed to mold and being sensitized to it. You could theoretically remediate a whole house if you have enough oregano oil. You would have to get it into a seriously potent gaseous state by nebulizing including in my opinion, cutting any hole into the drywall to get between it and the furring strips or whatever the outside structure is made out of as well. I have sprayed it in my car after exiting a moldy building so that I don't contaminate my vehicle . I can attest that that works. Years ago I did not have this system and I actually had to get rid of a car after I moved out of a moldy apartment. I do not know about the efficacy of porous surfaces such as wood. Again it is mixed with water. I do know that Oregano oil can be mixed with alcohol, as confirmed with the support team at NOW Foods which supplies therapeutic grade 100% oil of oregano. I hope this helps someone. I personally have entered a building where I could smell mold and subsequently sprayed all of my clothing with the mixture. Leave in an enclosed bag for few hours and launder.. there's literally no smell of mold on the clothing after the oregano oil and the fumes of the oregano oil have penetrated the clothing with the seclusion in this manner.

  • I have also heard about Dawn dishsoap I assumed that it was due to a High formaldehyde content in it. Another poster mentioned surfactant use. Jan 13, 2020 at 20:44
  • Hello, and welcome to Home Improvement. This is more of a discussion than an answer to the original question; you should probably take our tour so you'll know how best to contribute here. Jan 13, 2020 at 22:11

Spraying every surface and the complete room's air volume (also inside cupboards, shelves etc.) with a flower or garden sprayer filled with 25% vinegar + 1 drop of dish washing detergent helps immediately and is less poisonous. But protection glasses should be used and the breath should be hold.

After drying, an ozone generator can be applied. Repeat both if necessary.

Airing rooms in high humidity areas should be done only if it is dark outside - preferably before sunrise -, since the air is cooler and has statistically less humidity.

A humidity tester is important to keep the figure always below 70%.


FEMA has a good PDF on the basics of mold removal. Short version: Remove compromised material, bleach, sand wood to remove spores. Wear a 30 dollar silicone 3M half mask at the minimum. It will cost less than the box of disposable masks you'll burn through and actually protect you.


My 2 cents...

I used a store bought mold remover and a wire brush. Soak, scrub and repeat.

I wore a full suit like someone who paints cars and eye protection.

I used an N100 mask (3M 8233)

When satisfied I removed it all I painted over it with Kilz.

Put in new insulation.


If you have a serious mold problem in your home, get a professional to treat it. No home remedy is going to help in that case.

TSP has essentially been taken off of the market. It was used often to prep for painting in the past. There are TSP substitutes, but this stuff is dangerous.

My allergist recommended cleaning with white vinegar solution to remove/control mold in the home on a regular basis in the bathroom, refrigerator, etc.

Borax is still readily available. You can find it in the grocery in the laundry detergent aisle. As for it causing inhalation injuries, don't snort it. Sheesh, everything is dangerous if not used properly/according to directions. I use borax with every load of laundry I do. It is a great, inexpensive laundry booster and cleaning agent.

Someone was asking/hoping they could get their hands on some "sodium chloride." Look in your kitchen cabinet.... it's table salt.

  • If you have a mold problem in your house, you have a water problem in your house. Fix the water problem, or the mold will just keep turning up over and over again. Mar 5, 2017 at 22:44
  • They meant sodium chlorite NaClO2... Mar 20, 2019 at 22:59

Not the answer you're looking for? Browse other questions tagged or ask your own question.