How To Prevent Condensation & Mould In Bathrooms

What Causes Mould On Walls?

Black mould growth & moisture go hand in hand. Mould is caused by moisture, either from an internal or an external source. While our guide focuses on condensation, it is important to understand the varying sources of moisture and to identify what source of moisture is affecting you before you attempt to address it.

External

External sources of moisture come in a number of forms. These sources of moisture generally come in the form of penetrating damp & rising damp. Firstly, penetrating damp is caused from water ingress on exterior walls. This is due to wind-driven rain absorbing into exterior walls, as mineral surfaces such as brick, stone & concrete are porous, meaning they uptake moisture. The more porous the surface, the more water it will absorb.

Once the moisture enters the external wall, it can pass through the external wall into the inside of the property, causing large-scale internal damp. This is particularly the case with solid wall properties as there is no cavity to stop this transfer of moisture. Having said this, houses with cavity walls can also be at risk as poorly fitted insulation or any debris in the cavity can recreate this bridge for the moisture to transfer through.

In any case, penetrating damp can be identified by dark staining on external walls, internal mould, walls that are damp to the touch, crumbling plaster and by any signs of damage to the external wall, such cracked bricks & crumbling mortar. Crucially, penetrating damp can occur at any level of the building, which helps to identify it compared to rising damp.

Rising damp in contrast occurs at the ground level, when moisture from the ground is absorbed by the ground-level bricks. This rising damp is caused by a failure or non-existence of a damp proof course (DPC), which prevents the transfer of moisture from the ground by creating a water resistant layer. Rising damp is a rarer form of external water ingress that can lead to damp problems, such as crumbling plaster and damaged skirting boards.

Internal

The other potential cause of mould growth is internal condensation. The simplest way to help prevent condensation from building up inside your home is to improve the ventilation of your house by opening windows and using extractor fans when possible in order to allow the condensation to escape. In winter months it is sometimes not possible to have windows open, which can worsen the problem.

Furthermore, the temperature of the property can influence the ability for condensation to form. With cooler temperatures. condensation can more easily form on internal walls. Along with this, when clothes are dried on radiators, not only is their ability to heat the room reduce, but the moisture that comes off the clothes gathers in the room.

You can often find that this mould grows behind furniture where there is a lack of air circulation.

When it comes to bathrooms, generally mould growth especially on ceilings is due to the high moisture levels caused by showers & baths. If this mould growth gathers in the corners of ceilings and walls, this is also an indicator that it is an internal source of moisture in the form of condensation.

The Impact Of Mould On Health

The most important impact that mould can have is on the health of those that occupy a property that suffers from black mould. Mould is a form of bacterial growth that produces allergens & irritants that can cause a reaction either from touching mould spores or by inhaling them.

According to the NHS website, damp and mould in your home can have a particular impact on:

• Babies and children
• Elderly people
• Those with existing skin problems
• Those with respiratory problems, such as allergies and asthma
• Those with a weakened immune system

How To Remove & Prevent Mould

External

When it comes to external sources of moisture, there are ways to prevent mould. The only solution to prevent rising damp is to seek the advice of a damp expert who can implement a DPC to prevent the damp.

In the case of penetrating damp, whether you have a brick, stone or rendered exterior wall, this ingress of moisture can be prevented by applying a waterproofing coating. These work to prevent water ingress by creating a water repellent surface on exterior walls. It is crucial that whatever waterproof treatment you use, it must be highly breathable. If you use a non-breathable product such as a sealer, this will trap any moisture inside the wall, leading to damp problems and damage.

There are two options; a waterproof masonry paint or a masonry cream. While a waterproof masonry paint creates a coloured finish, masonry cream creates invisible waterproof protection that is perfect if you want to maintain a natural brick finish. Emperor Paint offer both a masonry paint and masonry cream that are super hydrophobic, highly breathable and have a proven 25+ year performance in all weather conditions. These have been developed to help prevent the numerous problems that penetrating damp can cause.

Both Emperor Masonry Paint & Masonry Cream come with a lifetime guarantee, ensuring their performance for decades to come.

Internal

Mould thrives in cold, moisture-rich conditions. When it comes to black mould growth in bathrooms caused by condensation, by preventing the formation of condensation on internal walls, you can significantly reduce the growth of mould long-term.

There are number of ways to easily reduce condensation, including improving ventilation, using dehumidifiers & increasing the use of heating. However, this is sometimes not enough to prevent mould from growing in rooms that are subject to consistent exposure, such as bathrooms. For this reason, anti-condensation paint & anti-mould paint was developed, which aims to prevent the formation of condensation on interior walls, thus reducing the ability for mould to grow.

Anti-condensation & anti-mould paints work in different ways. Some contain biocides that kill mould growth, ensuring it can't grow. The problem with these products is that they do not prevent the root cause of the mould, which is the moisture.

There are more advanced technologies available such as the Glass Microsphere technology from Suretherm. Suretherm Anti Condensation Paint is an internal water-based emulsion that significantly reduces the ability for condensation to form in the first place. By significantly reducing condensation, mould does not have the required conditions to grow.

It achieves this by absorbing heat from other sources such as the central heating, similarly to how a battery charges. This is heat that would previously have escaped through the wall and out of the property. By retaining heat twice as long as a standard emulsion paint, Suretherm can prevent the formation of condensation, which is made easier on cold walls.

If you are looking for a mould treatment for walls, Suretherm is the long-term solution that will prevent the problem at source.

What You Will Need:

• Suretherm Anti-Condensation Paint
• Cleaning solution
• Medium-pile roller
• Masking tape
• Paint tray or kettle
• Cloth
• Filler & sandpaper (if required)

Step 1: Preparation

Before any DIY project, you must ensure you put time into preparing the surface to be painted. This is the secret to achieving beautiful, long-lasting results, trust us!

The bathroom wall must be clean, dry and free from anything that can interfere with the adhesion of the paint. This includes removing the mould before you paint.

Start by removing any loose and failing paint from the wall using a scraper, if required. The moisture may have caused bubbling or peeling paint over time, so be sure to check carefully before moving on.

Remove all mould using a suitable cleaning solution such as Zinsser Mould Killer. You could use another cleaning solution, including a bleach solution by mixing a small amount of bleach with water. Start by wiping the wall down using hot soapy water to remove the initial layer of mould, followed by spraying the cleaning solution on to the surface and allowing it to dry. This does not need to be removed before painting as it will have killed any mould growth ready for you to paint.

If you have any surface damage such as cracks or holes, these can now be filled using an interior filler. Work the filler back and forth with a filling knife, ensuring that the defect is fully filled. Once left to completely dry, sand down to a smooth edge using sandpaper. Wipe down the surface to remove any surface dust, as this can lead to peeling paint if left.

Once the surface is completely clean & sound, apply masking tape to any edges and protect the floor using a dust sheet to prevent any paint splatter.

Step 2: Painting

Once the surface is ready, you can begin to paint. Start with your first coat of paint, firstly painting around the edges of the wall or ceiling using your paint brush. Once this is done, you can then use a medium-pile roller to paint the rest of the surface and to roll back over as close to the edge as possible to remove any brush marks.

Once you have applied you first coat of paint, leave it to completely dry which will take 4 hours. Once dry, it is time to apply a second coat. Apply the second coat, again starting with the edges and finishing with a roller to paint the rest of the surface.

The chances are is that you are painting your bathroom ceiling white, which is ideal as Suretherm comes in white as standard as the product cannot be coloured. Having said this, if you want a coloured finish then do not worry, you can paint over the top of Suretherm with any paint of your choice. You can also apply wallpaper over the top, without impacting the performance of the product.

Once dry, you can overcoat the area you have painted using a paint of your choice. We recommend using a washable paint such as Crown Trade Clean Extreme Scrubbable Matt as this can be easily washed using a cloth without marking the paint.

Frequently Asked Questions

Q. Can you use an anti-mould paint?

There are a number of anti-mould paints on the market that will help to prevent mould growth. Generally, these products will kill mould before it grows thanks to fungicides within the product. This can be undesirable to many and does not prevent the moisture problem. An anti-condensation paint is designed to prevent the formation of condensation, which is why it is the product we recommend.

There are a number of mould inhibiting paints such as Crown Trade Mould Inhibiting Eggshell if you are looking for an anti-mould paint.

Q. How much paint will I need?

The amount of paint you will need completely depends on the size of the area you wish to paint. Suretherm comes with a coverage of approximately 9-10m² per litre. With two coats required, an area of 10m2 can be coated using 2L of Suretherm.

We hope this has answered any questions you may have had regarding preventing condensation & mould growth in bathrooms. If you would like any more help & advice, our team of experts are on hand. Why not send an email to the team at hello@paintersworld.co.uk or message us on social media? At Painters World we have a wide range of paints & decorating supplies available, so no matter the job, we've got the right tools for you. Plus, get FREE next working day delivery on all orders over £50.