How to Kill Mold with Bleach: Steps & Alternatives

Mold and mildew are not just an eyesore, they can be hazardous to your health. Bleach is a common household item that will help remove mold on surfaces in the home. Bleach has many benefits for killing mold, but it also carries risks if not used properly or with caution. 

Kill mold with bleach by mixing 1 cup of bleach with 1 gallon of water and spraying the mixture to the surface with mold. After an hour, scrub and rinse the surface before drying it up. Ensure the room has enough ventilation and you have put on protective gear such as a mask, goggles and gloves.

The bleach to water ratio for mold is 1:9 from the procedure above. The bleach concentration to kill mold is 10%. This concentration won’t kill mold immediately and is limited to nonporous surfaces like tiles. 

How to Kill Mold with Bleach

Does bleach kill mold?

Bleach kills mold but works best only on non-porous surfaces like tiles and tubs. Bleach is ineffective against porous surfaces such as wood, drywall, or concrete. Mold will spread its roots into porous materials and bleach, thus only killing the outer parts of the mold. Soon afterward, the mold regrows even stronger than before. 

A bleach mixture for mold will also kill black and white mold, although you’re better off calling for a mold expert to deal with dangerous molds such as black mold. Even during mold remediation, leave the building to avoid inhaling the airborne mold spores.

How to clean mold with bleach 

Use bleach to get rid of mold on nonporous surfaces as follows:

  1. Turn on the fan or open the windows to ventilate the house. 
  2. Wear protective gear like a mask, apron, goggles, and gloves since bleach is corrosive and emits dangerous chlorine gas. 
  3. In 1 gallon of water, add 1 cup of bleach, then pour some of it into a spray bottle. 
  4. Spray the mixture on the mold, then waits for at least 1 hour. 
  5. Scrub with a soft-bristled brush if the surface is rough or dirty. 
  6. Rinse with clean water, then allow the surface to air dry.

This method works on all nonporous surfaces, including basement walls, roofs, and floors. Not drying the surface cleaned of mold will only encourage the mold to regrow. Also, throw away all the items that came into contact with the mold, such as the brush and gloves. 

Why you shouldn’t use bleach to clean mold

You may need to avoid using bleach to kill mold for the following reasons:

Has health risks

Using bleach to clean mold may have adverse health effects. Chlorine bleach is an acidic and hazardous chemical because it can irritate the nose, throat, and lungs when inhaled or swallowed. It is possible to experience eye, skin, and respiratory irritation from exposure to bleach. The chlorine released can also cause cancer through its byproduct called dioxin. 

These effects result from acidic bleach releasing chlorine gas when in use. You should never mix bleach with ammonia as the reaction between them emits toxic fumes (nitrogen trichloride and hydrazine) that are harmful to your health. 

Has environmental risks

Bleach has been linked with groundwater contamination through its manufacturing process. This process involves significant amounts of salt contaminating groundwater sources when disposed improperly into rivers or lakes. It also causes significant problems globally by leading to algae blooms.

Can damage surfaces and fabrics

Using bleach for cleaning mold can result in damaged surfaces, curtains, or clothing because the bleach cannot distinguish between different types of materials. Bleach will deteriorate many everyday household items like counter tops, carpets, drapes, etc. 

The strong chemical compounds that make up chlorine bleach also cause deterioration over time on various building components, including metals, plastics, rubber gaskets, and other seals found around doors and windows. These are necessary parts of buildings (and homes). This means that everything is at risk from exposure to concentrated amounts of chemicals such as bleach, even when used sparingly.

Does not work on porous materials

Bleach doesn’t work well on porous materials such as drywall, carpeting, and wood paneling. Bleach’s chemical setup prevents it from soaking up into the material and killing mold from within or removing stains. Bleach can work well for non-porous surfaces because when applied, it won’t seep into anything else but its intended area. 

With bleach being made up of 90% water and 10% chlorine, the chlorine will evaporate, leaving the water behind. This further encourages the remaining mold to regrow. 

As stated by the Environmental Protection Agency (EPA), always call for a professional mold cleaner if the mold covers more 10 square feet or more. Mold remediation should help do away with the mold and mildew permanently. 

Bleach alternatives for removing mold

Given the shortcomings of bleach in killing mold and mildew, the alternatives available include the following:

White vinegar

Pour undiluted white vinegar into a spray bottle, then spray it on the moldy surfaces. After 1 hour, wipe the surface with a cloth and air dry. You don’t need to rinse it off. 

White vinegar is an effective cleaning agent that can be used as a substitute for bleach and kill mold on porous surfaces such as wood. It has acetic acid and is typically available in the market, just like household bleach which you probably already have at home. When comparing bleach vs. vinegar for mold, vinegar is the better option.

This type of vinegar contains acidic solid properties, making it easy to kill mold and mildew. There is no need to rinse after application, unlike chlorine-based cleaners such as bleach or most store-bought cleaners. White vinegar dissolves dirt naturally, so this method works well even on tough stains.

Avoid using vinegar on aluminum, cast iron, waxed wood, and natural stone surfaces, as it can damage the surface. You can, however, easily remove mold from wood with vinegar.

Tea tree oil

Add 2 teaspoons of tea tree oil in 2 cups of white vinegar or 2 cups of water then pour the mixture into a spray bottle. Spray the moldy surface, wait for 1 hour, then wipe the surface dry. 

Tea tree oil is a natural fungicide, antiseptic and antibacterial agent. It’s effective in treating ringworm, athlete’s foot, jock itch, tinea versicolor, and other skin infections because it penetrates deep into pores where the fungus resides. 

Tea tree oil kills 99.99% of pathogens, including yeasts & molds, without damaging other cells or tissues. It won’t damage the surfaces when used to clean surfaces, unlike bleach. 

Hydrogen peroxide

Mix water and hydrogen in equal parts, then spray the mold with the mold-killing solution. After 1 hour, rinse and wipe the surface dry. 

Hydrogen peroxide is a mild bleach alternative for removing mold. Hydrogen peroxide will kill the mold after about an hour, but it may leave behind a yellow stain. If you don’t need to immediately use something on surfaces that won’t be harmed by leaving overnight or longer, try using white vinegar as a bleaching agent instead of store-bought chemicals like Hydrogen Peroxide or Clorox.

Baking soda

Dissolve 2 tablespoons of baking soda in 2 cups of water, then add the solution to a spray bottle. Spray it on the moldy surface, then scrub after an hour. Rinse the surface, then spray the baking soda solution on the surface again. Let it air dry. 

With baking soda, you can also remove mold from grout. It’s a homemade mold killer that kills mold by dehydrating it. 

Grapefruit juice extract

Add 10 drops of grapefruit juice extract into 1 cup of water, then add to a spray bottle. Spray the surface with the mixture. Wait for 15 minutes, then wipe the surface dry. 

Grapefruit juice extract is used in cleaning mold since it’s acidic and is safe to use on all surfaces. Salt paste

Mix equal parts of baking soda and table salt with just enough warm water to make a thick paste. Apply the paste to the moldy surface, then wait for 15 minutes. Scrub with a brush, then rinse before drying the surface. 

The salt kills the mold spores by dehydrating them, making them unable to grow and reproduce. If the salt paste doesn’t work to remove all of the mold from an area, use vinegar instead since salt isn’t very effective at removing mildew stains alone. 


Mix equal parts of ammonia and water the spray the mix on the surface with mold. After 3 hours, scrub and rinse, then let it air dry. 

An ammonia solution is an excellent natural mold removal solution. Ammonia contains alkaline molecules that can dissolve the cellular structure of molds, killing them instantly. Even if some parts of the fungi remain after total removal, they will not be able to survive on non-nutritious surfaces, so this is an effective way to kill all fungi entirely and prevent future growths.

Signs of mold 

Some of the signs that your building has mold include the following:

  • A musty and earthy smell in your home. 
  • Musty smell from the air conditioner. 
  • Damage to materials such as wood.
  • Dark lines on the grout between tiles. 
  • A persistent cold and fatigue. 
  • Peeling paint or wallpaper.
  • Dark spots on the wall, especially where there is moisture, and it’s dark. 
  • Itching when you put on certain cloths. 
  • Worsening of some respiratory problems such as asthma and allergies. 

These issues point to different levels and types of mold infestation in the home or office. If you can’t identify the mold immediately, better call a mold expert since some mold can be very dangerous to human life. 

How to prevent mold 

Prevent the growth of mold through the following methods:

  • Stop leaks that cause dampness on surfaces. Stopping leaks requires checking around windows frames, roofs, gutters, etc., and ensuring pipes are joined properly with glue and other adhesives.
  • Keep the building ventilated by keeping the windows open and using fans to circulate the air in the building. 
  • Keep surfaces dry and clean. For instance, users can place a dehumidifier in the basement or laundry room. Keeping surfaces dry means keeping humidity levels below 50%.
  • Carpeting should not be placed in locations of your house that may get wet, like the kitchen or bathrooms. Always dry rugs as soon as they get wet. If already infested with mold, throw them away. 
  • It is also important not to use too many chemicals on floors as they might damage walls and paintwork that are damp from water leakage.
  • Clear and repair any gutters and downspouts to ensure water from the rain flows away from the walls. 

If an area has already been contaminated by mold spores, it will be more difficult to prevent future outbreaks if there are still moisture problems within the house itself.

Still, the best way to remove mold is to call for a mold remediation expert who will assess the source of the mold and the extent of its growth, then kills and prevents its regrowth. Clorox can kill mold, but it’s not as effective as what a mold remediation expert will do.

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