How to Paint a Bathroom Properly: Moisture, Mould, and the Right Paint

Bathrooms are the most demanding rooms in any home when it comes to paintwork. The combination of steam, condensation, direct water splashes, temperature fluctuations, and often limited ventilation creates an environment that will quickly expose any shortcuts in preparation, product choice, or technique. A poorly painted bathroom can begin to show mould, peeling, and discolouration within months. A properly painted bathroom, using the right products and methods, will look fresh for years.

This guide covers everything you need to know about painting bathrooms correctly, with a particular focus on the challenges found in London properties, from period homes with limited ventilation to modern apartments with internal bathrooms.

Understanding Moisture in Bathrooms

Before choosing a paint or picking up a brush, it helps to understand what is actually happening to the walls and ceiling of a bathroom when it is in use.

A hot shower or bath produces a significant volume of water vapour. This warm, moist air rises and comes into contact with cooler surfaces: the ceiling, the upper walls, the window glass, and any area where the room meets an external wall. When the warm air meets a cooler surface, the moisture condenses, forming water droplets. This is the condensation you see on mirrors, windows, and tiles after a shower.

The same process happens on painted walls and ceilings, but it is less visible. The paint surface becomes wet, and if the paint is not formulated to handle this, several problems follow:

• Moisture penetration: Standard emulsion paints are porous. Repeated wetting allows moisture to penetrate through the paint film and into the plaster beneath, eventually causing the paint to lose adhesion and peel.
• Mould growth: Mould spores are present in every home. They need moisture, warmth, and a food source to grow. A damp bathroom with standard paint provides all three. The paint itself, along with the dust and dirt that settle on it, provides sufficient nutrients for mould.
• Efflorescence: On new plaster or in areas where moisture has penetrated, mineral salts can be drawn to the surface, leaving white, powdery deposits that push through the paint film.
• Staining: Persistent moisture can cause yellowing, water marks, and general discolouration, particularly on ceilings directly above the shower or bath.

Ventilation: The Most Important Factor

No paint, however advanced, can compensate for poor ventilation. If your bathroom does not have adequate ventilation, addressing this should be the first priority, before any painting work.

Natural Ventilation

A bathroom with an openable window has a significant advantage. Opening the window during and after bathing allows moist air to escape and dry air to enter. In older London properties, particularly Georgian and Victorian homes in areas like Chelsea, Kensington, and Notting Hill, bathrooms were often fitted into rooms with sash windows, providing excellent natural ventilation.

If your bathroom has a window, use it. Even in winter, cracking the window open for fifteen minutes after a shower will dramatically reduce condensation.

Mechanical Ventilation

Many London bathrooms, particularly those in converted flats and apartments, are internal rooms with no windows. These bathrooms rely entirely on mechanical extract ventilation (an extractor fan) to remove moist air.

Building Regulations (Approved Document F) require bathrooms without openable windows to have mechanical extract ventilation capable of removing at least 15 litres per second of air. The fan should be connected to the light switch, ideally with an overrun timer that keeps the fan running for at least 15 minutes after the light is turned off.

If your extractor fan is inadequate, noisy (which discourages people from using it), or not working at all, replacing it is one of the most effective things you can do to protect your bathroom paintwork. A good-quality, quiet extractor fan from a brand like Vent-Axia or Xpelair costs relatively little and will pay for itself many times over in reduced maintenance.

Heated Towel Rails and Underfloor Heating

A warm bathroom dries out faster. Heated towel rails and underfloor heating raise the surface temperature of the room, reducing the amount of condensation that forms and helping it evaporate more quickly. Both are excellent investments for London bathrooms, particularly those with limited ventilation.

Choosing the Right Paint

Standard Emulsion: Why It Fails

Standard matt emulsion, the type used on walls and ceilings throughout the rest of the home, is not suitable for bathrooms. It is porous, allowing moisture to penetrate, and its surface texture provides a foothold for mould. Even vinyl silk emulsion, which has a slightly less porous surface, is not specifically formulated for wet environments and will eventually fail in a busy bathroom.

Bathroom-Specific Paints

Several paint manufacturers produce paints specifically formulated for bathrooms. These products typically incorporate some or all of the following:

• Moisture-resistant film: The paint forms a tougher, less permeable barrier than standard emulsion, reducing moisture penetration.
• Anti-mould additives: Fungicides and biocides are incorporated into the paint to inhibit mould growth on the surface.
• Enhanced adhesion: Better bonding to the substrate reduces the risk of peeling in humid conditions.

Here are the leading bathroom paint products available in the UK market:

Dulux Trade Bathroom+

One of the most widely used bathroom-specific paints, Dulux Trade Bathroom+ is a water-based matt emulsion with built-in anti-mould protection. It is moisture-resistant, wipeable, and available in a wide range of colours via the Dulux colour mixing system. It offers a genuine matt finish, which many homeowners prefer, while still providing the performance needed for a bathroom environment. Allow two coats over a suitable primer on new plaster.

Little Greene Intelligent Matt Emulsion

Little Greene's Intelligent range is not marketed specifically as a bathroom paint, but its formulation makes it exceptionally well-suited to wet environments. Intelligent Matt Emulsion is highly washable, moisture-resistant, and durable, while maintaining the beautiful flat matt finish that Little Greene is known for. It is available in all of Little Greene's extensive colour range and is particularly popular for heritage properties in Belgravia, Mayfair, and Kensington where homeowners want a premium finish throughout.

Farrow & Ball Modern Emulsion

Farrow & Ball's Modern Emulsion is their washable, wipe-clean formulation, recommended for kitchens and bathrooms. It provides the characteristic Farrow & Ball depth of colour in a more durable finish than their Estate Emulsion. While not as overtly moisture-resistant as a dedicated bathroom paint, it performs well in bathrooms with adequate ventilation.

Zinsser Perma-White

For bathrooms with persistent mould problems, Zinsser Perma-White is a specialist option. It is a self-priming, moisture-resistant paint with a five-year guarantee against mould and mildew. Available in matt, satin, and semi-gloss finishes, it is particularly useful for problem areas such as ceilings above showers and internal bathrooms with limited ventilation.

Crown Trade Clean Extreme Anti-Bacterial Scrubbable Matt

Crown's Clean Extreme range offers anti-bacterial and anti-mould properties with a scrubbable finish. It is a practical, hard-wearing option that performs well in bathrooms and is competitively priced compared to premium heritage brands.

Finish: Matt, Satin, or Gloss

The finish you choose affects both appearance and performance.

Matt finishes look the most elegant and are increasingly popular in bathrooms, particularly in high-end London properties. Modern bathroom-specific matt paints are formulated to be moisture-resistant, so a matt finish no longer means poor performance in a wet environment. The main trade-off is that matt surfaces are slightly harder to wipe clean than satin or gloss.

Satin finishes offer a soft sheen that is easy to clean and sheds moisture effectively. Satin is a good middle-ground for bathrooms, offering better practical performance than matt without the full reflectivity of gloss.

Gloss finishes are rarely used on bathroom walls and ceilings in contemporary schemes, but they remain the best choice for woodwork, skirting boards, and window frames in bathrooms, where a hard-wearing, water-shedding surface is essential.

Preparation

Treating Existing Mould

If your bathroom has existing mould, it must be treated before any painting begins. Painting over mould will not kill it. The mould will continue to grow beneath the new paint and will eventually push through.

To treat surface mould:

1. Apply a mould treatment solution. HG Mould Spray, Zinsser Mould Killer, or a solution of one part bleach to four parts water will kill surface mould. Spray or sponge it on, leave for the recommended time, and then wipe clean.
2. Allow the surface to dry completely. This is essential. Painting over a damp, recently treated surface will trap moisture and create the conditions for mould to return.
3. Apply a stain-blocking primer if the mould has left staining. Zinsser B-I-N (shellac-based) is the gold standard for blocking mould stains and preventing bleed-through. It dries in minutes and can be overcoated within an hour.

Preparing the Surfaces

Good preparation is as important in a bathroom as in any other room.

• Fill any cracks or holes with a flexible filler. Bathrooms experience more thermal movement than other rooms, so a rigid filler may crack over time.
• Sand the walls lightly (180-grit) to provide a key for the new paint.
• Wash the surfaces to remove soap residue, body oils, and other contaminants that can affect paint adhesion. Sugar soap is effective for this.
• Prime any bare plaster with an appropriate primer or mist coat. New plaster should be allowed to dry fully before painting, which can take several weeks.

Sealing Around Baths, Showers, and Basins

Before painting, ensure that the sealant around your bath, shower tray, and basin is intact. Failed sealant allows water to penetrate behind fittings and into the wall, causing dampness that will eventually manifest as paint failure and mould growth in adjacent areas. Use a quality sanitary silicone sealant from a brand like Dow Corning or Everbuild.

Painting Technique

Ceilings

The bathroom ceiling is the hardest-working surface in the room. Hot, moist air rises and hits the ceiling first, making it the most prone to condensation and mould. Give the ceiling particular attention:

• Use a bathroom-specific paint or a product with anti-mould properties.
• Apply two full coats, ensuring even, complete coverage.
• Consider a satin rather than matt finish for the ceiling, as it will shed condensation more effectively.

Walls

In a standard bathroom layout, only a portion of the wall area is exposed to direct water. Tiled splashbacks behind the bath, basin, and shower protect the most vulnerable areas. The exposed painted walls above and around the tiled areas should be painted with a bathroom-specific product.

If you have an open shower area without a full tile surround, the adjacent walls will be subject to significant direct water exposure. In these areas, paint alone may not be sufficient, and tiling, glass screens, or specialist waterproof panels may be more appropriate.

Woodwork

Skirting boards, door frames, and window frames in bathrooms should be painted with a durable, moisture-resistant finish. An oil-based eggshell or satinwood from a brand like Little Greene or Dulux Trade will provide the best durability. Water-based alternatives such as Dulux Trade Diamond Satinwood are also effective and have the advantage of lower odour and faster drying.

Special Considerations for London Properties

Period Bathrooms

Many London period properties have bathrooms fitted into rooms that were not originally designed for the purpose. High ceilings, ornate cornicing, and large sash windows are common features. These rooms can be challenging to paint due to their height and detailing, but they also benefit from better natural ventilation than modern bathrooms.

For period bathrooms in conservation areas or listed buildings, paint colour and finish may be subject to heritage considerations. Little Greene and Farrow & Ball both offer extensive heritage colour ranges that are available in bathroom-suitable formulations.

Basement Bathrooms

Basement bathrooms are common in London townhouses, particularly in areas like South Kensington, Pimlico, and Fulham. These rooms often have limited natural light, no windows, and a tendency towards dampness due to their below-ground position. They require the most robust approach to paint specification, ventilation, and mould prevention. A dehumidifier can be a useful addition to a basement bathroom.

En-Suite Bathrooms in Apartments

Modern London apartments frequently have compact en-suite bathrooms with internal layouts and minimal ventilation. These rooms benefit from a powerful, quiet extractor fan and a paint system that can handle daily high humidity without failing.

Professional Bathroom Painting

Our bathroom painting service addresses every aspect of painting a bathroom correctly. We assess the ventilation, treat any existing mould, carry out thorough preparation, and apply a paint system specified for the conditions of your particular bathroom. We work with all the leading paint brands and can advise on the best products for your requirements and budget.

Whether you have a compact en-suite in a Fulham apartment or a grand period bathroom in a Kensington townhouse, we understand the specific challenges that London bathrooms present and deliver a finish that will look fresh and resist mould for years to come.

Maintaining Your Bathroom Paintwork

A well-painted bathroom requires minimal maintenance, but a few simple habits will extend the life of the paintwork:

• Ventilate after every bath or shower. Open the window or run the extractor fan for at least 15 minutes.
• Wipe down surfaces that are prone to condensation, particularly around the window and on the ceiling above the shower.
• Address any mould spots immediately. A quick spray with mould treatment will prevent a small patch from becoming a major problem.
• Maintain sealant. Replace cracked or discoloured sealant promptly.
• Repaint every three to five years, or sooner if the paint shows signs of deterioration. Regular repainting is far less expensive than dealing with the consequences of long-term moisture damage.

A bathroom painted with the right products, applied correctly over proper preparation, with adequate ventilation to support it, will remain fresh, clean, and mould-free through years of daily use.