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Read More About Black Mould - FAQS

Black Mould - FAQS

We provide answers to your most frequently asked questions about black mould.

What is black mould?

Black mould is the common name used to refer to fungi that are found in damp or water-damaged buildings. These include Cladosporium, Alternaria and Stachybotrys chartarum. You can recognise fungi growth by areas of dark green, grey or black slime. 

Stachybotrys chartarum

Stachybotrys spores by Brendon Rawlings via Wikimedia Commons

Is black mould harmful?

In some cases, prolonged exposure to black mould can be harmful, especially for the elderly, infants or asthmatics as well as those with skin and respiratory problems. Mould produces allergens but some forms can also release mycotoxins that can aggravate respiratory conditions. It can also cause fatigue, headaches and breathing difficulties if left untreated. For more information on Mould and Health read this from the NHS. You can also read our piece on the health risks of  mould.

Where does black mould grow?

Black mould thrives in moist areas and is commonly found in:

  • Bathrooms
  • Basements or cellars
  • Underneath kitchen and bathroom sinks
  • Underneath or behind refrigerators
  • Behind walls that also house plumbing
  • Near air-conditioning units
  • Around windows 
  • Under carpet that is frequently damp

Mould can grow on a range of surfaces including painted walls and ceilings, wallpaper, carpets, and tiles.

Click through for more help identifying and treating damp. 

What causes black mould?

Mould is often caused by high humidity in your home. If you have excess moisture in the air that can't escape then it creates the conditions for mould to grow. Poor ventilation is therefore one of the most common causes. Building faults that lead to damp also create conditions for the fungi to thrive. 

How does black mould grow?

Black mould thrives on moist surfaces, particularly bathroom ceilings, crevices on bathroom walls and window sills. Bathrooms are extremely moist and humid rooms. When moist air comes into contact with air at a lower temperature, mould begins to grow. Mould is an asexual organism, meaning one single pore can asexually reproduce trillions of mould spores in the space of a few days.

If not visible, how can I tell if my bathroom is suffering from mould?

One of the first warning signs of mould growth is a slightly unpleasant musty smell. The smell may be rather earthy, indicating that the wood from underneath your flooring is beginning to rot.

Your bathroom may develop spongy floorboards usually indicating the wood beneath is beginning to rot and decay.

Tiles may become loose due to rotting beneath the tiles’ surface. Moisture tends to cling on the mastic between the shower/bathtub and the walls. This causes the caulking to crack, allowing excess water to seep behind the shower or bathtub wall.

Condensation leads to a rapid and unhealthy spread of mould and rots so it is important to act fast to prevent any black mould outbreaks.

You can read our guide on how to kill mould in bathrooms.

mould on grout caulking behind sink


How to cure black mould growth?

A good scrub down with a specifically formulated cleaner like Mould Wash Concentrate will get rid of mould, algae, and mildew on many surfaces including masonry, tiles, wood and painted surfaces.

Mould Wash Concentrate is a surface biocide cleaner, which is used as a cleanser before anti mould paint can be applied. Prepare the surface by removing any debris from the surface, including flaking paint, mould and dirt. Once the area is clean, simply wash down the surface with the diluted Mould Wash Concentrate using a sponge or cloth.

After the surface has been cleansed and has dried completely, you can now use anti-mould paint to cover the surface. Note that whenever painting over mould, you should always use anti-mould paint as other paint products will not prevent any further outbreaks.

Anti-mould paint is specifically designed to protect against unsightly and unhygienic black mould. Made with highly-advanced biocides with proven results, anti-mould paint can guarantee 5 year protection.

Ideal for walls and ceilings in homes and commercial buildings, anti-mould paint is the perfect solution to black mould infestations for all property types.

If you have a specific colour scheme that you would like to keep then we also sell anti mould paint additives that can be added to standard emulsion paints to make them mould resistant. 

Permagard have listened to our customers and created a mould remover kit that contains all you need to cure black mould

How else can I prevent future outbreaks of mould growth?

  • Increase ventilation in your house or flat, this may be by mechanical ventilation systems like our Nuaire Drimaster ECO PIV system, positive input ventilation units or by simply opening windows.
  • Ensure installed ventilation fans are turned on and working to reduce condensation/ moisture in the air.
  • Clean regularly – Clean your bathroom with bleach or a surface sanitiser at least once a week. Scrub your bathroom tiles and any dark crevices.
  • Light – mould thrives in moist, dark areas so allow a lot of light into your bathroom.
  • After a shower, wipe down all of the surfaces with a dry sponge or cloth. This will remove any excess water.
  • If your property suffers from condensation make sure to wipe this damp from the surfaces to reduce mould growth.
  • Move furniture like sofas away from walls so air can circulate behind them which reduces condensation occurring.
  • Avoid leaving damp towels or bath mats on the floor. Wash them regularly to prevent mould


View more mould treatments or explore your options when it comes to condensation control in your home. 


You can see an overview of the costs of damp proofing treatments.