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Three steps to getting rid of Black Mould 

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Step One – Treat the cause, not the effect

You need to treat the cause of the problem not the effect.  The effect is the black mould, the cause of the problem is humidity being generated.  This is why we generally recommend good quality humidity controlled extract fans to bathrooms and kitchens and any other areas where there is likely to be a lot of humidity such as a room which is used for drying clothes in.

Ceiling Black Mould

Ceiling Black Mould

Different types and styles of extract fans

As with most products, extract fans come in different styles and have different functionality.  The main thing you need from an extract fan is for it to be extracting!  We often find extract fans in houses have been switched off, which often when we enquire is due to the noise.  However, extract fans are essential for removing humid air.  There are several types of extract fans:


Basic Extract Fan

Basic Extract Fan

  1. One-off extract – this simply works when you switch the extract fan on and off.
  2. Activated extract fan such as via a light switch point – this is a fan that turns on and off when you switch the light on and off for example. Equally, it could be triggered by someone walking into a room with a more sophisticated system (although we have never seen one).
Designer Extract

Designer Extract

If your property has black mould call us on Freephone 0800 298 5424

In both these cases, they do extract assuming the fans are clean but only at the time they are in use; they require active effort to be switched on and off.  This is probably when an over-run is added to the previously mentioned system that allows the extract fan to over-run the time that it is switched on and off.  This can be a few minutes and it is usually something that can be set.  It is a much better system as it clears the air so to speak of the humidity.  However, in a heavily used bathroom there can still be problems with black mould in the house.

Humidity Controlled Extract Fan

These focus on the issue, which is the humidity, and switch on and off until the relative humidity is adjusted at a pre-set level.  This means that you can use the bathroom and have a shower, etc in the morning and the fan is switched on and off during the day when you are out with no activity or input required on your part; the fan works automatically.

The problem we have come across with these fans is that they can switch on and off on humid days and on some very humid days run most of the day as they are of course fighting a losing battle when the air is humid.  However, for the majority of instances we feel this is the best type of fan for most people.

Maintain and Clean Extract Fans

As mentioned, if an extract fan is dirty then it will not work properly therefore ensure that extracts are regularly cleaned and maintained.

An extract fan needs a cover or sometimes you can get backdraughts.  There are designer style fans that open and close which stop backdraughts.

Extract vent dirty

Extract vent dirty

Extract fan cover

Extract fan cover

Designer style extract fan

Designer style extract fan

Step Two – Cleaning Black Mould

Clean any walls that have black mould with chlorine bleach, it is normally one-part chlorine to about ten parts of water.  You will need to wear protective gloves and you will need a sponge to apply it with.  You need to apply it relatively sparingly with lots of elbow grease, not trying to soak the walls with water.  Ideally use something like a plant sprayer to spray the walls with it (you will need to throw the bottle away after you have used it).  You need a towel-like material that soaks up liquid and you need to dry the wall.


Be aware that even if you do clean it properly, as we have come across in a case recently, and then you carry on not treating the effect, i.e. still have extract fans that are broken or in this case you switch off the extract fans and don’t use them then the black mould will come back.


Do Dehumidifiers help with Black Mould?

A question that is often asked is do dehumidifiers work?  The answer is yes and no.  Dehumidifiers do deal with the humid air and are often used in situations where there has been a flood or something similar to help dry out walls or a builder on a tight contract who needs the plaster to dry out quickly so they can paint it.  By using a dehumidifier to deal with a humidity problem in a house you are living in, it is probably best to see if you can do something about the problem.  For example, if you are drying clothes in different rooms can you just dry them in one room and have a dehumidifier or even a humidity controlled extract fan added to that room.  Ultimately, it comes down to can you dehumidify and deal with the effect of the humidity.


We have also used a crystallised product as a temporary measure to draw moisture from a room and also help freshen it up.  This was once we had resolved the cause of the problem.



Be Careful

Also, be careful cleaning anything precious such as carpets, etc. as you will need to protect them or try a test area on the carpet to see how the bleach will affect it.

Carpets with Mould

If you are looking to clean carpets (we have literally seen mould in carpets) or furniture it very much depends upon how badly it has been affected with the black mould.  Do a sample area to see how it cleans; it may be that you need to throw it away.

Clothes with Mould

Clothes can also be affected by black mould; we have seen a property where clothes were kept in black bags to stop them from getting mouldy.  We feel it is probably best to throw anything away that has black mould on it if it does not come clean after washing.  Remember that unless you deal with the cause of the humidity then the problem will re-occur.

Step Three – How can you help get rid of black mould?

Clothes drying and black mould

This can range from everything such as making sure that clothes are dried in a room which has a humidity controlled extract fan, opening windows and not opening windows depending upon the relative humidity outside. Ventilation is always a difficult one, you need to get it right and not too cold.

Background heating to get rid of black mould

In some of the rooms you don’t use too often that have been left unheated it is worth adding background heat.

We would also look at buying yourself a relative humidity controlled heating system.  These have clocks/timers which switch on and off when the humidity gets above a certain level and help reduce condensation occurring in rooms that you do not use that often, for example the small bedroom that you store items or even within a roof space.  We have come across problems where the amount of stored items in a roof space has reduced the air movement in this area and the items in the roof such as old clothes, etc. can store damp and create black mould and other problems.

Roof air movement

Roof air movement

Roof full of stored items

Roof space full of stored items

Black mould – who are the experts? 

This is easier said than done.  Educate yourself with regard to looking after the house and about condensation and black mould; read anything that you find on black mould however be aware of who is writing the article and whether they have a vested interest, for example using their product.

In terms of our interest, we are more than happy to advise we are independent chartered surveyors looking to carry out a building survey or a defect report and this type of problem will be covered within the report.  We will give both a reasoned explanation as to what we think is going on and a solution with anticipated cost of the works we are recommending.  We would also add that we have recently seen a number of articles using the term ‘toxic mould’ and we would take these with a pinch of salt.

Black mould solution

Finally, we would add that we, and everyone involved in black mould, are still learning about it.  In many ways it is a relatively new concept as we have increased the insulation within our properties.

Other Articles on Condensation, Rising Damp and Black Mould

We have written many surveying articles on this subject which may be of interest to you:


Condensation and air movement

Condensation – do trickle vents work?

Rising damp and black mould


I have still got problems with black mould, I’ve tried everything – is it the building’s fault?

Sometimes you need to call in an expert to deal with the problem but we would first of all suggest you read and re-read our article and just make sure that you have covered everything.  We have dealt with defect cases and legal disputes where we feel it has been more attributed to the type of building than the occupier’s lifestyle although it is very difficult to be certain without lots of testing.  We have carried out data monitoring as mentioned and thermal imaging of properties along with tests on the dampness in the walls and carried out building surveys and we would generally comment that you are more likely to have a problem with black mould in:

Thermal image of apartment

Thermal image of apartment

Buildings with concrete elements

1960’s/1970’s property which has got concrete elements particularly on a flat/apartment development from this era with a concrete frame or concrete panels.

Concrete Frame Building

Concrete Frame Building

Airtight Buildings

We are also finding problems with properties from about the 1990’s onwards which are very highly insulated and airtight however there does not seem to be a consideration of the need for air movement in the property.

Extension of different construction

Existing houses that have had extensions added which are highly insulated against an older colder construction.

Having said that, where we have investigated these frequent problems we have come across that although extract fans are installed in bathrooms and kitchens they are not used and/or they do not have an over-run time to take the humidity out of the air.  The people living in the property then go to work and the humid air travels throughout the property to the colder areas such as in cupboards, around window reveals, carrying with it dirt, human skin, etc. to start the black mould growth.

Mould to Window

Mould to Window

Plastic double glazed windows without trickle vents

Other problems that we come across often is the installation of plastic double glazed windows that do not have trickle vents.  This then leads to comments such as that we have not changed the way we use the building but we are now getting condensation problems.  This is usually because the older windows were single glazed, possibly draughty and were not expected to perform that well and when a new window is put in without a trickle vent air can no longer move around a property and condensation occurs.

Trickle vents

Trickle Vents

Air movement via trickle vents

Air movement via trickle vents

Trickle vents

Trickle vents

Independent Surveyors

If you truly do want an independent expert opinion from a building surveyor, we are happy to do valuations, building surveys, structural surveys, structural reports, engineer’s reports, specific defects reports, home buyers reports or any other property matters.

Please contact us on 0800 298 5424 to have a free of charge friendly chat with one of our surveyors

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We hope you found the article of use and if you have any experiences that you feel should be added to this article that would benefit others, or you feel that some of the information that we have put is wrong then please do not hesitate to contact us (we are only human).