What paint stops mould coming back on a bathroom ceiling?

Why does mould keep coming back on the bathroom ceiling?

Mould needs moisture, and a bathroom ceiling gets plenty. Warm steam rises, hits the cooler ceiling and condenses into tiny droplets. If the room isn't aired, that film of water sits there for hours, and the black or grey spots follow, usually in the corners and above the shower first.

It tends to be worse in winter. Ceilings are colder and the air is damper: the Bureau of Meteorology's long-term averages for Frankston Beach show 3pm relative humidity of about 73 to 74 per cent in June and July, against about 59 to 60 per cent from December to March. Cold ceilings plus damp air plus a closed door is the recipe for a mouldy bathroom.

Can you just paint over mould?

No. Painting over live mould hides it for a few weeks, if that. The spores are still in the old paint and the plaster, and they grow back through the new coat, often looking worse because the fresh paint shows the stains more clearly.

Paint makers are consistent on this. Haymes says to always clean and remove mould before painting, and Dulux's instructions for its kitchen and bathroom paints start with killing the mould and letting the surface dry.

How do you kill mould before painting?

Dulux's product instructions give two options: a mould killer product, or a bleach solution of 1 part bleach to 3 parts water, left on for 15 minutes, then washed off and allowed to dry. Whatever you use, follow the label.

• Open the window and run the exhaust fan while you work.
• Wear gloves and eye protection, and never mix bleach with other cleaning products.
• Treat a margin around the visible spots, not just the black patches.
• Wash the treatment off and let the ceiling dry completely before any paint goes on.
• If the paint is flaking or bubbling, scrape back the loose paint once it's dry. Our guide on why paint peels and bubbles explains why.

What kind of paint should go on a bathroom ceiling?

Use a ceiling paint made for kitchens and bathrooms, not the ordinary ceiling white used in bedrooms. These wet-area paints have mould resistance built into the film. Dulux and Haymes both sell one, and several come with a written guarantee against mould growth that has its own conditions, so read the product page before relying on it.

Ceilings are normally done in a flat finish, which hides joins and patches when light hits them at an angle. Wet-area ceiling paints keep that flat look. For the walls, a washable low sheen made for bathrooms is the usual choice. Our guide to paint finishes room by room goes through the options.

• Kill and clean off the mould, then let it dry.
• Fix any flaking paint and stains, and prime or seal where the product calls for it.
• Two coats of a mould-resistant kitchen and bathroom ceiling paint.
• Leave the room well ventilated while it dries, and avoid long hot showers for the first day or two.

Is ventilation more important than the paint?

Usually, yes. Victoria's Better Health Channel says the simplest fix for mould is often just opening a door or window, and recommends using exhaust fans when showering or cooking, fixing leaks, and wiping away condensation.

A few habits make a real difference to how long a repaint stays clean:

• Run the exhaust fan during every shower and for a while afterwards. If it barely pulls a tissue, it may need cleaning or replacing.
• Crack the window or leave the door open after showering.
• Squeegee or wipe the shower screen and any droplets on the ceiling.
• Don't dry wet towels in a closed bathroom.
• If a clothes dryer is in or near the bathroom, make sure it vents outside.

When is it more than a paint problem?

Some ceilings need other trades before a painter. Brown water rings, sagging or soft plasterboard, or mould that returns within weeks of a proper clean all point to water getting in from above or poor ventilation that paint can't fix. Get the leak or the fan sorted first, then repaint once the ceiling is dry and sound.

Better Health also notes that mould can trigger symptoms like a blocked nose, cough and wheeze, so if someone in the house has asthma or a weakened immune system, it's worth dealing with sooner rather than later and keeping them out of the room while it's cleaned.

Should I do it myself or get it done?

A small bathroom ceiling with light spotting is a manageable job if you're comfortable up a ladder and follow the product instructions. It's a bigger job when the old paint is peeling, the mould has come back more than once, or the whole house is due for a repaint anyway.

When we paint wet areas as part of an interior repaint, the ceiling is treated and cleaned before any paint goes on, and your written quote says which products are used. We use Dulux on every job.

Quick questions

Sources

What this guide relies on. Product advice changes, so check the maker's current instructions for the exact paint you're using.

1. Mould and your health — Better Health Channel, Victorian Department of Health
2. Wash&Wear +PLUS Kitchen & Bathroom Low Sheen: preparation — Dulux
3. Why you need mould-resistant paint for your bathroom ceiling — Haymes Paint
4. Climate statistics for Frankston Beach (086371) — Bureau of Meteorology