Dealing with mould and mildew stains: The right prep and paint system for bathroom and kitchen ceilings

Mould and mildew growth, particularly in bathrooms, kitchens, and utility rooms, is a frustratingly common problem in the UK. It’s not just an aesthetic issue; it can be a sign of poor ventilation and a potential health hazard. When warm, moisture-laden air (from showers, cooking, or dryers) hits a cold surface, condensation forms. This moisture, combined with the porous nature of standard matt paint, creates the perfect breeding ground for mould spores.

As a homeowner or tenant, your first reaction might be to simply wipe it down and paint over it. However, if you skip the critical preparation and use the wrong product, the mould will return, often within a few months, bringing the black stains back through the fresh paint film.

Identifying the root cause

Before you even pick up a brush, you must understand why the mould is growing. Painting over the problem without fixing the cause is a guarantee of failure.

Condensation (The most common cause)

This occurs when high internal humidity meets a cold spot (the ‘dew point’).

• Where it occurs: Ceilings, particularly around the edges of external walls, cold corners, and window reveals.
• The fix: Improve ventilation. This means installing or upgrading extractor fans, ensuring they have an adequate run-on time (at least 15-20 minutes after the room is vacated), and heating the room slightly to raise the surface temperature.

Water ingress (The structural cause)

This involves external water leaking into the structure.

• Where it occurs: Often appears as a distinct watermark, sometimes yellow or brown, and can be isolated to a single area (e.g., below a gutter, near a leaking pipe, or around a chimney stack).
• The fix: A decorator cannot solve this. You need to call a plumber or roofer to fix the leak and allow the masonry to dry out fully before decorating.

Note: If the plaster is crumbling, bubbling, or feels wet to the touch, you have water ingress and must call a specialist for structural repair first.

Step 1: Prepping the surface like a professional

This step is the most important part of the entire process. You cannot paint over active mould spores.

Safety first

Mould spores can be respiratory irritants. Ensure you wear:

• Safety goggles.
• Gloves.
• An FFP3-rated dust mask to prevent inhaling airborne spores.
• Good ventilation (open windows, but seal the door to the rest of the house).

How to prep ceiling for mould painting

1. Remove visible mould: Start by removing the surface mould. Do not scrape dry mould, as this releases spores. Wipe the area with hot, soapy water first.
2. Apply a fungicidal wash: Use a dedicated fungicidal wash or a specialist mould remover to kill any remaining spores that have penetrated the paint film. Products like diluted household bleach (1 part bleach to 4 parts water) or proprietary mould killers are effective. Apply it beyond the visible mould area. Do not rinse the fungicidal solution; allow it to dry thoroughly according to the product’s instructions to ensure maximum spore kill.
3. Scrape and sand: If the existing paint is bubbling or peeling (a sign the mould was attacking the adhesion), gently scrape off the loose paint to a sound edge. Sand lightly with fine-grit paper (around P120) and clean the dust away thoroughly.
4. Stain blocking (If required): If the mould has left a dark, deep stain that persists after cleaning, a professional may use a shellac-based stain blocker like Zinsser B-I-N. This ensures the dark stain doesn’t bleed through the new paint layers.

Step 2: Selecting and applying the anti-mould paint system

Once the ceiling is dry, spore-free, and sound, you can apply the protective paint system. You are looking for a product that is not just moisture-resistant but contains a biocide that inhibits the growth of mould on the paint film itself.

One of the most trusted names in professional mould treatment is Zinsser Perma-White. This product is specifically formulated for high-humidity areas like bathrooms, kitchens, and laundry rooms, however there are also other options:

Paint System	Key Benefit	Ideal Use
Dulux Easycare Bathroom	MouldTec technology, highly moisture and steam resistant, wide colour range.	Standard family bathrooms and kitchens where condensation is moderate.
Crown Trade Clean Extreme	Trade-grade durability, anti-microbial protection, available in scrubbable matt.	High-traffic areas, rental properties, or commercial kitchens.
Anti-Condensation Paints	Contains thermal microspheres to raise the surface temperature, preventing condensation formation.	Rooms with severe cold spots (e.g., North-facing bedrooms or older homes).
Paint Additives	Biocidal additives (e.g., Dryzone Anti-Mould Additive) can be mixed into any standard paint (non-vinyl) to achieve mould resistance.	When you need a specific, non-mould resistant colour or brand but require protection.

Why hire a professional to fix mould on the ceiling?

While the cleaning process might seem straightforward, hiring a skilled painter and decorator to fix your mould problem can make the process a lot less stressful:

1. Root cause diagnosis: A professional will correctly diagnose if the issue is simple condensation or complex water ingress, preventing unnecessary painting.
2. Specialist products: They have access to professional-grade fungicidal washes, stain blockers, and anti-mould paint systems (like trade-specific versions) that are superior to off-the-shelf retail options.
3. Flawless finish: They ensure the ceiling is prepped, stains are properly blocked, and the anti-mould paint system is applied evenly for a smooth, lasting finish that is guaranteed against fungal degradation.

Mould is a perennial problem in the UK, but with the right preparation and the right anti-mould paint, you can achieve a long-lasting, clean ceiling. But, if there is only one thing you take away from this article: do not simply wipe and paint!

With Rated People, you have the power to get it done. Find a trusted, local tradesperson today.