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Does Bleach Actually Kill Mould? Everything You Need To Know

spray bottle

Bleach is thought to be the be all and end all of mould removal. So, it may come as a surprise that bleach doesn’t actually kill mould as well as you may think.  

Read on to find out if bleach effective on mould, its drawbacks and when to seek the help of a professional mould removal service.  

Does Bleach Kill Mould?

It can, but its effectiveness is varied. 

There’s evidence bleach can kill fungi, but it needs to have a concentration of at least 10% to work. Even then, it cannot penetrate porous materials like plaster, wood or grout.

Bleach only kills mould on the surface of porous materials, leaving the membrane to continually grow beneath.  

So yes, bleach has the ability kill mould, but it’s only useful on non-porous surfaces like sinks and tiles at a 10% concentration.  

So, Can I Use Bleach To Kill Mould Myself?

MouldMen doesn’t support the use of any homemade bleach DIY solutions to eliminate mould as they simply aren’t effective.

However, commercially made DIY products containing quaternary ammonium compound and a sodium hypochlorite base solution can help eliminate mould. 

Considerations For Using Bleach To Kill Mould

Before slathering bleach over every mouldy surface, there’s a few things you’ll want to know: 

  • Bleach with a concentration high enough to kill mould can also corrode tiles and grout, making them more porous and susceptible to mould growth. 
  • Bleach can remove the colour of mould rather than the mould itself. You’ll think the mould is gone, when in fact, the bleach has just made it invisible. This allows the mould to continue to grow and spread undetected.   

What About Store Bought Bleach Products?

Commercially available mould cleaning products may look like they’re doing the job, when in fact, they’re just masking the problem.  

Most of them use bleach (often listed as sodium hypochlorite) as an active ingredient. However, the concentration of bleach in these products marketed as ‘mould killers’ is often only 5% or less. 

Health Concerns For Using Bleach

Bleach is a corrosive substance that can cause a variety of health concerns. Prolonged exposure can cause irritation of the mouth, eyes and lungs and even burn the skin if not rinsed off immediately after contact.  

You should never mix bleach with ammonia, vinegar, drain cleaners or other acids as it can release a toxic chlorine gas.  

Mould Removal Alternatives To Bleach

The health risks and environmental implications of bleach can be off-putting for many people. For a natural, non-chemical alternative to bleach, try one of these solutions: 


Vinegar is well known as a natural mould treatment. To clean mould with vinegar: 

  1. Pour undiluted vinegar into a spray bottle and spray directly onto the mouldy surface. 
  2. Let it sit for an hour. 
  3. Use a soft bristle brush to scrub the mouldy surface until the mould is gone.  
  4. Dry the area completely. 

Tea Tree Oil

Tea tree oil has antifungal properties, making it a helpful treatment for mould spot removal. Here’s how: 

  1. Mix one teaspoon of tea tree oil with 2 cups of warm water in a spray bottle.  
  2. Apply the solution to the mould affected area and leave for 20 minutes. 
  3. Sponge off the mould with warm water. 

Professional Mould Removal Services

It is important to note that the above remedies only work as temporary mould removal treatments. For large or recurring patches, it’s best to seek the help of a professional mould removal service to safely remove the mould and determine the root of the cause.  

The MouldMen team will inspect, treat and provide you with a Mould Management and Prevent Plan to ensure that your home is kept safe and free from black mould. Call us on 1300 60 59 60 to book your free inspection today. 

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