Evidence of moisture and mould on internal wall in house

Why Is There Mould in my Flat?

5 September 2023

If you have noticed that black mould has begun to spread in your flat, then obviously you are going to be concerned.

The most important thing to understand at this stage is how that black mould has found its way into your flat. Once you understand that, then it’s going to be a lot easier for you to get rid of that same mould once and for all.

So, why is there mould in your flat, and what can you do to remove it when you discover it?

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Why is My Flat Mouldy?

Condensation mould growing on interior walls in house


To start off, let’s address the root causes of mould, and how they can lead to black mould growing in a flat.

First off, black mould is nearly always the product of damp. Damp provides the perfect environment for black mould to grow, with the spores that grow into the fruiting body recognisable as black mould thriving in the environments created by damp.

So, to learn why your flat is mouldy, you first need to discover why your flat is suffering from damp.

There are three main causes of damp in a property, and if you are living in a flat then there will definitely be one cause more likely than the others.

First you have rising damp. Rising damp is the process of moisture travelling upwards into your properties walls from the ground, through a process known as capillary action. Rising damp normally never travels more than about three foot, or one meter above ground level, so unless you are situated in a flat on the ground floor, then it’s not going to be likely that rising damp is the cause of the damp in your flat.

Then there is penetrating damp. Penetrating damp is usually down to a fault in the property itself, something like a leaky pipe or broken guttering can contribute to damp spreading in a flat quite easily, and is much more likely to be the property defect responsible for damp rather than rising damp.

Lastly, you have condensation. Condensation is the cause of damp most likely to be responsible for the conditions allowing mould to grow, so we will look a little closer at the different causes and reasons that condensation worsens.

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Why Does My Flat Have So Much Condensation?

Condensation running down a window

Condensation is the by-product of living an everyday life. Actions like cooking, washing, drying clothes, exercising – all of these things create warm moist air, which condenses onto cold surfaces on contact, when that same warm air cools down, turning the moist air from a gas to a liquid.

Realistically, any action that creates moisture in the air is going to contribute to condensation. That’s why it’s advised that people who live in spaces without access to generous levels of ventilation keep an eye on the amount of moisture rich air they create, as it can easily lead to a condensation rich environment.

The key to eliminating condensation is an increase in the amount of ventilation. Your flat should have access to a healthy amount of ventilation, be it in the form of an extractor fan, window vents, the ability to open windows and create an airway through the flat – however it may be, ventilation is the best way to reduce the levels of condensation in your flat.

You can learn more about the different ways condensation builds up in a flat here, but if you are unsure why your flat is suffering from high levels of condensation then you can always arrange for a condensation survey from our team here.

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Need Help With Condensation? Call 0800 288 8660

How Do I Stop Condensation from Causing Black Mould?

Surveyor drawing plans on tablet outside property

With condensation being such a common problem in flats across the UK, its no surprise that there are plenty of flat-dwellers looking for a rock solid solution to the build up of condensation, and the resulting black mould, in their own home.

To stop condensation from causing black mould, any warm moisture created in your flat needs to ventilated safely. This might mean the addition of an extractor fan, the opening of windows, or even being more mindful of the activities that create moisture.

Shorter showers, using lids on pots when cooking, or drying your washing outside if possible (or in a well ventilated room) are all great ways of reducing the level of condensation in your flat.

You can also look into the layout and general state of your flat, and decide if that might be contributing to the high level of condensation allowing the black mould to grow.

A high level of clutter, for example, is something that can allow condensation to worsen. This is simply because a high level of clutter restricts the natural airflow in a flat, whilst also providing more surfaces onto which the condensation can land.

You can read much more about how you can reduce the level of condensation in your flat here, but we can tell you with certainty that if you don’t eliminate the condensation (or the other form of damp) allowing the black mould to grow, then you are only going to see the problem return time and again.

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Call 0800 288 8660 to Request a Condensation Survey, or

How Can I Clean Black Mould?

Mould Kit

The good news is that once the source of the damp has been eliminated, it will be fairly easy for you to clean away any black mould that might have been growing in your property.

So, in most cases black mould can be cleaned away fairly easily. You are going to need a few basic items; a bucket, a sponge (or anything you can scrub with), a black mould treatment spray (available from our online shop), and some protective gear to protect yourself from the black mould spores that will be released when its disturbed. (I would make reference here to buying a mould eradication kit and link to the shop)

First, you will want to spray the effected area with the black mould treatment spray. Once the mould is covered, you can scrub it with the sponge to make sure all of the black mould has been coated. When it is coated, we recommend leaving it for about half an hour to let the treatment have a full effect.

Once those thirty minutes are up, scrub it again and see if all of the black mould is removed. If not, just repeat the process until the surface is clear.

It really is as simple as that. What comes next is the restoration of the area affected by the black mould, and this might not be so simple. Depending on the surface effected, you might have to look into replacing what the black mould has ruined, as it can have a disastrous effect on some surfaces.

For example, if left alone for long enough black mould can potentially ruin wallpaper. The mould itself will cause the paper to dry out and become brittle, not to mention the nasty discolouration and blotting that the mould will cause. You might be able to ignore or patch up the wallpaper, but depending on the spread of the mould you may well end up with a ruined pattern, and have to re-paper the area.

Then there is plasterboard. Plasterboard is another surface that black mould can have a dreadful effect on, with the mould ruining the finish and overall surface of the plasterboard, potentially meaning that if the black mould infestation is bad enough you are going to have to look into having the wall either reskimmed, or entirely replastered.

If the black mould has spread to a fabric, again, it may be beyond repair. You can do your best to give it a thorough wash, and this might help to remove the spores and mould embedded within the fabric, but depending on the severity of the black mould infestation, you might have to accept defeat and look into new carpeting, or sofas, if your efforts to clean are unsuccessful.

Harder surfaces like tiles, hardwood, laminate flooring, they are all going to be amongst the easiest surfaces to clean as it will be harder for the black mould spores to penetrate the harder exteriors these materials have. Usually a good black mould treatment spray and a healthy scrub, and you can expect to clean up the black mould pretty easily.

Remember, you should only attempt to clean black mould once the source of the damp has been addressed and eliminated. Cleaning the mould before the damp has been dealt with is like shovelling snow when it’s still snowing – you might clear the mould in the short term, but the spores will still be present and ready to grow if the damp conditions continue.

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Help Removing Black Mould

If you are struggling with black mould in your flat, then you can always talk to our team about discovering the cause of the mould, or even for advice on how to clean it away. You can call 0800 288 8660, or you can request a call back online via the form below, and our team of property care experts can help to guide you through the black mould removal process.