Getting Rid of Black Mould in Homes

Black mould affects thousands of properties every year in the United Kingdom, often caused by the way buildings are constructed and DIY draft proofing which reduces the natural ventilation of a property. This can cause an unpleasant internal environment, especially during periods of cold weather, while black mould can damage walls, furnishings and can even pose health risks.

If you are concerned about a black mould problem in your home, there are steps you can take to alleviate the problem. It is essential to act quickly to understand what is causing the problem, and while wiping away black mould works short term, generally the appearance of mould indicates a serious damp problem that may even require professional assistance. Moulds of different colours will thrive in damp spaces with a lack of ventilation and potential health issues for the young, elderly and those who suffer from allergies. While black mould is a term most people use, not all mould is black, it can also be green, brown, red, yellow, grey or white. All can cause health issues for some susceptible people.

Rentokil Property Care have been providing advice and specialist solutions for damp and mould problems in homes for decades, and we can provide you with professional treatments that address the root cause.

Sometimes a minor black mould problem can be fixed with DIY options, while other homes may require professional chemical cleans, ventilation improvements and treatments to increase the thermal efficiency of a property. A damp survey carried out by a CSRT or CSTDB qualified professional surveyor can help provide you with answers if you are concerned about black mould in your property.

While specks of black mould around window frames is relatively common in homes during the colder months, if the problem worsens this may indicate an imbalance in the internal environment.

There are several reasons why you may have black mould in your home:

The most common cause of black mould forming is from moisture being trapped inside the home and condensing on walls, giving black mould spores the perfect environment to germinate and grow.

Everyday activities from bathing, drying clothes, washing and even breathing contribute moisture in the atmosphere, which is known as humidity. If water vapour is unable to escape it will cool and condense on cold surfaces.

You may notice beads of water forming on or around windows, on walls and ceilings. These surfaces are damp to the touch and this moist environment creates the conditions for mould to form. The problem is often made worse in winter, as occupants close windows and stop other forms of natural ventilation, trapping moisture inside the property with nowhere to escape.

With excess moisture being produced, unless there is an outlet to remove the water vapour in the air, it will condense on cold surfaces.

British homes were often built with open fireplaces and chimneys, single glazed windows and were generally draughty - this allowed moisture to escape through natural means during periods of bad weather.

Now fireplaces are boarded up, double glazing is installed, while insulation is increased, meaning moisture has less escape roots, despite the same amount of moisture being produced within homes.

Partly down to the typical British weather, during winter we don’t open our windows or ventilate our homes enough to allow the damp air to escape.

So unless there is ventilation in the form of window trickle vents, extractor fans, kitchen hoods, PIV units and air bricks, moisture will remain trapped inside.

To prevent black mould from forming you need to increase ventilation and air flow throughout the property.

Moisture vapour can circulate through your property and will condense on cold spots, meaning that moisture produced in a kitchen could condense on cold spots in other rooms, especially external north facing rooms and walls.

Often solid wall constructed properties suffer from cold bridging, as there is no cavity to create a thermal barrier for the property. Bay windows will also be prone to cold bridging, as they project forward from a property and therefore cool easily.

To prevent this you need to improve the thermal efficiency of walls. Thermal plastering and anti-condensation paints can be used to increase the thermal efficiency of walls, helping remove cold spots where more traditional insulation methods are not suitable.

While sometimes not practical or possible, the best way to keep a property warm enough to prevent condensation is to have low background heating on throughout the day.

Short bursts of high heat may seem more cost effective, but as the warm air cools again, its ability to hold moisture drops, meaning that it will condense on cold surfaces. This is why condensation forming on windows is notable in the mornings, as the temperature inside the property drops over night. The World Health Organisation suggests indoor air quality in living areas is best around 18-20°C.

Sometimes black mould can occur because of plumbing issues such as leaking pipes or appliances. Penetrating damp can also cause black mould to form, as moisture penetrates through the fabric of a building, creating a cold spot where warm humid air inside the property can condense.

As the main cause of a black mould problem is not always clear, a damp survey can provide answers and solutions from a trained and qualified professional surveyor.

Black mould can appear in different places throughout the home, and can often require different methods to prevent the problem. Ultimately you need to consider where the excess moisture is coming from, and try to control its production and remove it from the property.

Black mould forming on walls is a common problem but understanding the root cause of the problem is essential. When walls are cold, moisture in the air will condense on the surface, making them damp to the touch, and in extreme cases beads of water will run down the wall and can even lead to timber skirting boards rotting.

When large furniture and wardrobes are pushed up against the wall, stale stagnant air becomes trapped and can lead to mould forming.

Often black mould will form on external north facing walls as these surfaces receive the least sunlight, and are therefore some of the coldest areas in the house. Leaking pipes built into the walls, and penetrating damp can also cause mould to form, so a thorough investigation is key before repairs are carried out.

When rearranging a room you may discover black mould forming on walls behind bedframes, chest of drawers and bedroom cupboards, and sometimes even forming in built-in wardrobes.

It is very common to find mould growth behind furniture in rooms with poor ventilation and air flow. When moisture laden air becomes trapped it will condense on the cold surfaces, providing ideal conditions for mould to form. This is also the cause of ‘dust shadows' forming behind furniture as dust can 'glue' to the damp wall.

Improve the ventilation by ensuring furniture is not pushed up against the wall by allowing air flow and keeping the room at a constant temperature.

Mould can easily develop on any surface with the right moisture content, and often insulated ceilings can have cold spots due to missing insulation where moisture can condense. Mould can form in uniform patterns where a panel of insulation is missing between joists. In some cases where there is no insulation at all, mould will form across a ceiling, especially in sloped ceilings which are not easy to insulate. Black mould can also form on loft hatches as these are often not insulated. Insulation improvements are required to help prevent these issues.

Steam forming on windows is the first sign of a condensation problem, and often small specks of black mould are nothing to worry about, and can be wiped away. If water is running down window frames pooling on window cills, and black mould is forming around windows, this could indicate a bigger issue. Address the excess moisture being produced and open window trickle vents to help remove it from the room.

Drying wet clothes on radiators is a common cause of mould forming on windows, as the moisture cannot escape. Try to dry clothes in a room with the window open and the door closed, this will allow moisture to escape, rather than condensing around windows.

Kitchens are one of the main areas where moisture is produced in the home. Extractor fans should be used at all times when cooking on the hob, and when using pans of boiling water it is essential to use pan lids to stop vapour from escaping through the property. Leave extractor fans on for 10 minutes after cooking, and try to keep kitchen doors closed so the moisture cannot circulate throughout your home.

With hob canopies, make sure you know if they extract moisture outside or just filter cooking smells and return the moist air to the room.

Bathing and washing produces steam which will condense on cold surfaces. Make sure to use the extractor fan and keep your door shut. It is common for condensation to form in bedrooms adjacent to ensuite bathrooms, doors are left ajar or the extract turned off and moisture can then escape into the bedroom. When running a bath start by filling the bottom with cold water before adding hot, this will help reduce the amount of steam created.

Black mould forming on surfaces can be a worrying occurrence, and often the solution required is unique to each property, so the action taken will depend on several factors.

While small changes to moisture production may reduce the amount of moisture in the air, improving ventilation is one of the most effective long-term solutions to prevent mould caused by condensation. This can be carried out by using extractor fans, the installation of PIV units or opening window trickle vents.

When black mould is forming on walls and ceilings, you may need thermal improvements. Black mould on ceilings could indicate missing loft insulation, while external walls can be affected by cold bridging. Thermal plastering and anti-condensation paints can be used to increase the thermal efficiency of internal wall surfaces, helping remove cold spots where more traditional insulation methods are not suitable.

When black mould is forming behind furniture or in bay windows, you can increase the air flow by moving furniture away from the walls. Whilst wiping away isolated areas of black mould may work for some, if the problem persists and DIY fixes do not work, you may require professional assistance.

A CSRT or CSTDB qualified surveyor from Rentokil Property Care can provide you with answers on why you have black mould forming in your property, and can offer advice and treatment options for a long term solution.

The first step is to try and remove the excess moisture from your home by improving ventilation - this will remove the conditions needed for mould to grow. You can attempt to wipe away black mould from surfaces, and if the source of moisture has been addressed it may not return. If you have allergies, make sure to use gloves and a mask, while a mixture of liquid soap and water can be used to remove the mould.

If DIY attempts to remove the mould have only provided a temporary fix, you may require professional solutions. Professional mould cleaning, and recommendations for long term solutions may be required.

You can remove mould from painted walls by using a mix of liquid soap and water, but if you have allergies, make sure to wear gloves and a mask when carrying this out. If the black mould has been left for some time, often the paint can be stained and deteriorated. A two part steriliser and cleaner system may be required to remove the stain. Areas affected may need repainting as a last resort.

You must address the source of moisture that caused the problem in the first place, and consider thermal improvements to cold walls. It is far easier to deal with a mould problem early than to let it spread and cause more costly damage, both to decorations and the health of occupants.

Make sure that skirting boards are not warped or rotten by condensation, as this could also indicate further issues that need to be addressed. 

To prevent black mould from returning you need to control the levels of moisture within the home, while improving ventilation to help remove the humid air. Identify areas where black mould is forming, and make efforts to improve air circulation by moving furniture.

While dehumidifiers may reduce moisture in one room, they will stop working once the water tray is full, which can limit their ability to provide an effective long term solution. Installing extra ventilation or a PIV unit after a professional survey may prove a better long term investment.

You may require professional help from a trained and qualified damp surveyor - they can provide you with recommendations and remedial treatments.

Black mould can be worrying, so if the problem persists in your home you could benefit from professional assistance, as this can help provide a long term solution.

Rentokil Property Care will be able to provide you with a damp survey, giving you the peace of mind that comes with a professional inspection. Rentokil Property Care are experts in damp and condensation solutions, and have been offering professional damp surveys for black mould for decades.

Our CSRT and CSTDB qualified surveyors will take the time to thoroughly investigate your property, while using a range of methods and specialist tools to identify the root cause of the problem. This will include the use of thermal imaging cameras to identify cold spots, checking the ventilation requirements, and providing  guidance to effectively control excessive moisture.

All findings will be detailed in an easy to read survey report, along with recommendations for treatments where necessary. This may include thermal improvements to walls, increased ventilation or insulation top ups.

Rentokil Property Care has been working in peoples homes and businesses for over 70 years, correctly identifying property issues and providing long term solutions.

We are experts in property preservation, and can provide you with personalised advice for the black mould problem affecting your property.