The Complete Guide to Painting a Bathroom: Products, Process and Avoiding Mould

Why Bathrooms Fail Faster Than Any Other Room

Bathrooms are the hardest environment for any paint system. Every shower generates steam that condenses on walls and ceilings; every bath introduces sustained humidity; cleaning products — bleach, limescale remover, tile spray — are corrosive. The combined effect degrades ordinary emulsion within months and creates the conditions in which mould spores thrive.

Yet many bathrooms in London are painted with the same product used throughout the rest of the house, because it's convenient and the difference only becomes apparent a year later when you're looking at black spots in the corners and peeling paint around the shower tray.

The correct approach to bathroom painting is not complicated, but it does require choosing the right products and addressing the root causes of moisture rather than painting over them.

Step One: Investigate Before You Paint

If you have existing mould in the bathroom, do not simply paint over it with an anti-mould product and consider the problem solved. Mould is a symptom, not the cause. Before any painting:

Check ventilation: Is there a working extractor fan? Does it duct to outside air or into the roof void? A fan that circulates air into the loft space without exhausting it outside is ineffective. The extractor must be ducted to a vent at the soffit, eaves or external wall. If the fan is undersized or failed, replace it before spending money on decoration.
Check for structural damp: Black mould on external walls, particularly at low level or in corners, may indicate condensation driven by a poorly insulated or cold bridge wall rather than just high humidity from showering. Insulating behind the surface or improving heating in the room is the fix, not anti-mould paint.
Check around the shower tray and bath: Failed silicone joints allow water to get behind tiles and into wall substrates. This water then works its way through plasterboard or plaster and appears as damp patches, blistering paint or efflorescence. Re-sealing the bath and shower tray before painting is non-negotiable.

Removing Existing Mould Correctly

Before applying any paint to a previously mouldy surface:

Apply a mould treatment — Zinsser Mould Killer or Ronseal Mould and Mildew Remover — to all affected areas according to the manufacturer's instructions (typically leave on for 15 minutes, wipe off)
Allow the surface to dry completely — at least 24 hours in a warm, ventilated room
Apply Zinsser Bulls Eye 1-2-3 Primer or Zinsser BIN Shellac Primer over any stained areas. These primers stain-block and provide a sound base for the topcoat even on surfaces that have previously been discoloured by mould or water.

Do not skip the primer stage. Anti-mould topcoats alone will not prevent mould reoccurrence if the surface below is still discoloured and the spores have not been properly treated.

Correct Paint Products for Bathroom Walls and Ceilings

The market distinguishes between 'kitchen and bathroom paint' (a marketing term applied to various products with varying levels of moisture resistance) and genuinely moisture-resistant coatings. What you actually need:

Dulux Trade Bathroom+ or Dulux Endurance Kitchen & Bathroom: A vinyl emulsion with added mould inhibitor and moisture resistance. Provides a soft sheen finish that is reasonably wipeable and resistant to condensation. Adequate for most family bathrooms that are well-ventilated.

Farrow & Ball Full Gloss or Modern Eggshell: Farrow & Ball's modern water-based eggshell has better moisture resistance than their Estate Emulsion and is appropriate for bathrooms, although it is more expensive. The Full Gloss is the most moisture-resistant option in their range and provides a durable, wipeable surface.

Zinsser Perma-White Interior: A specific formulation designed for high-humidity environments, with a guaranteed anti-mould performance. It dries to a hard, semi-gloss finish. Not the most beautiful product, but highly effective in problematic bathrooms that have had repeated mould issues. Can be tinted to custom colours.

Little Greene Intelligent Matt Emulsion: Performs better in bathrooms than many standard emulsions due to its breathable, mineral-rich formulation, but is not a dedicated bathroom product. Best used in bathrooms that are well-ventilated and have never had significant mould problems.

For ceilings, the same bathroom-spec product should be used as on the walls — ceilings are typically the worst affected surface because warm humid air rises and condenses there first.

Painting Over Tiles: Is It Worth It?

Painting over ceramic or porcelain bathroom tiles is possible but is a compromise solution. It is appropriate where:

Retiling is not in the budget or is impractical (e.g., the tiles are well-bonded to the wall and removal would damage the plasterboard substrate)
The tiles are in good structural condition but the colour or pattern is dated

The correct system for tile painting:

Clean tiles thoroughly with a degreaser (sugar soap or a dedicated tile cleaner). Grease and soap residue are the primary causes of tile paint adhesion failure.
Apply a dedicated tile primer: Zinsser Bulls Eye 1-2-3, Johnstone's Trade Aqua Primer, or a specific tile primer such as Ronseal One Coat Tile Paint Primer. Sand smooth lightly with 240-grit between primer and topcoat.
Topcoat with a hard-wearing enamel or tile paint: Dulux Kitchen & Bathroom Tile Paint, Rust-Oleum Tile Transformations, or a two-pack epoxy enamel for maximum durability. Two full coats minimum.
Re-seal all silicone joints once the paint has fully cured (typically 7 days for most enamel products) — not before, as fresh silicone can interfere with adhesion.

The limitations: painted tiles will not be as durable as glazed ceramic; they will show wear around grout lines over time; and they cannot be cleaned with abrasive cleaners. Expect a painted tile finish to last 4–7 years in regular use with care.

Ventilation: The Long-Term Solution

Every paint system in a bathroom is compromised if the ventilation is inadequate. The standard for bathroom extraction is a minimum of 15 litres per second (54 m³/hour) for an intermittent fan. The fan should run for at least 15 minutes after the shower ends — either with a humidistat control or a timer overrun.

Trickle ventilation through window frames (in casement windows with trickle vents) supplements but does not replace an extractor fan.

If the bathroom has no external window and no extractor, it needs an extractor before it needs new paint.

We Specify Bathroom Decoration Correctly

If your bathroom has had repeated mould or paint failure problems, or if you simply want the decoration done right the first time, contact us for a free assessment and quotation. We'll identify the root cause of any moisture issues, specify the correct products, and deliver a finish built to last in the most demanding room in the house.