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Bathroom mildew treatment

Updated: 23 October 2026

The ceiling above the shower was black again three weeks after you sprayed it. Bathroom mildew treatment can clear a small surface stain. It will not hold if the room stays humid, the fan stops with the light, or the mould is inside the sealant. This page stays in that wet room. It is not the whole-house buying tree and not the sequence before emulsion. Which bottle fits a wall, a tile, or fabric is on the [mildew treatment comparison](/hub/paints-and-varnishes/mildew-treatment). Peter F. updated this page on 23 October 2026. Humidity figures are publishers' guidance, or one reviewer's meter, not a pass mark for a spray. Our amazon.co.uk links may earn a commission at no extra cost to you.

The ceiling above the shower was black again three weeks after you sprayed it. Bathroom mildew treatment can clear a small surface stain.

Our top picks

Mold Armor Mold Armor FG516 mould blocker 946 ml

Best overall

Mold Armor Mold Armor FG516 mould blocker 946 ml
8.2/10about £25.47
View offer
Professional Strength Professional Strength bleach-free mould remover 500 ml

Best value

Professional Strength Professional Strength bleach-free mould remover 500 ml
8.0/10about £9.99
View offer
Strewth Strewth mould preventer spray 500 ml

Alternative

Strewth Strewth mould preventer spray 500 ml
6.6/10about £14.99
View offer
On this page
  1. 1.Why bathroom mould returns
  2. 2.What to clean, and what to replace
  3. 3.What the three listings say about wet rooms
  4. 4.Humidity numbers you can use carefully

Why bathroom mould returns

Most black specks on a bathroom ceiling are condensation. Warm shower air hits a cold ceiling and drops water. National Energy Action's leaflet says run the extractor for about 20 minutes after you bathe, with the door shut and trickle vents open. A reading that never falls is the problem: a fan tied to the light, laundry on the radiator, a window painted shut. Shelter England says landlords should not dismiss the pattern as "just condensation" without checking for a leak.

What to clean, and what to replace

A stain on tile or in porous grout can be a surface clean if you wet it with a product the label allows and you do not dry-brush. GOV.UK still wants a mask, gloves, and goggles, and a mould product rather than bleach. If the mould is under the silicone, HG and UniBond say replace the sealant. None of the three listings claims to rebuild a bead. Strewth names seals. Naming a seal is not renewing it. If the bead is cracked or black all the way through, cut it out once the surround is clean and dry, then apply a fresh sanitary sealant. Masks and dry-brushing are on how to use mildew treatment.
Mold Armor Mold Armor FG516 mould blocker 946 ml

Testsieger

Mold Armor Mold Armor FG516 mould blocker 946 ml
8.2/10about £25.47
View offer

What the three listings say about wet rooms

Strewth is the preventer at £14.99 for 500 ml, about £29.98 per litre, with 3.8 from four reviews. Bullets say spray on and leave, with no wipe. The only UK text saw a return within about two weeks in the high 70s to 80s percent relative humidity, then about two months after dehumidifiers. If your bottle says do not wipe, that line still stands. Professional Strength is the bleach-free 500 ml remover at £9.99, about £19.98 per litre, 4.2 from 15 reviews, and the title names bathrooms and walls. No text gives a duration. Mold Armor FG516 is the top pick only under a 500-review rule. The listing surface is fabric. The only UK text in a sample of 50 saw no instant change on a bathroom ceiling. Who each bottle is for is on best mildew treatment.

Humidity numbers you can use carefully

If a hygrometer stays above 60 percent for hours after a shower, Ashfield Council says damp and mould become more likely. Healthy Homes expects faster activity around 70 to 80 percent. Those percentages are not a laboratory test of any bottle. If the ceiling still blacks in the same cold corner once the air is drier, look for a leak or a fan that is painted shut. A second bottle will not move air that the fan does not extract. The label checks are the mildew treatment buying guide.

Common questions

Why does the ceiling go black again after I spray it?
The ceiling is getting wet again. Condensation from showers lands on a cold surface, and a spray does not warm the plaster or run the fan. If the room is drier and the same patch returns, look for a leak or a cold loft. Mold Armor's only UK review in a 50-text sample saw no instant change on a bathroom ceiling, and that listing is for fabric.
Is 60 percent humidity already a problem?
Ashfield Council says relative humidity that stays above 60 percent may lead to damp and mould. Healthy Homes describes about 40 to 65 percent indoors, bathrooms a little higher, and faster activity around 70 to 80 percent. A spike during a shower is normal. These figures are guidance, not a test a spray has passed.
Should I wipe the spray off grout?
Follow the bottle. Strewth's bullets say spray, leave, and do not wipe. The only UK review wiped to remove mould and then left product on. One Professional Strength review says wash the growth down first. That is that person's order, not a universal grout rule.
Can a spray save black silicone?
It can clean growth on the face of the bead. It cannot rebuild silicone that is mouldy underneath. HG and UniBond both say replace the sealant when the mould is in the joint. Strewth lists seals and does not say it renews a failed bead.
How long should the fan run?
NEA suggests about 20 minutes after bathing, door closed, trickle vents open. Treat that as a leaflet tip, not as the extract rate in Approved Document F. If you rent and the fan is dead, report it. A longer dwell on the spray will not replace extracted air.
Which kept bottle names bathrooms or seals?
Professional Strength's title names bathrooms, kitchens, and walls. It is £9.99 for 500 ml, bleach free on the listing, 4.2 from 15 reviews, with no stated duration. Strewth names tile, grout, walls, and seals, at £14.99. Mold Armor names fabric, not a painted ceiling. Neither wall bottle prints an HSE number in the scrape.
What should I tell a landlord?
Say where the mould is, how often it returns after a small clean, whether the fan runs on, and whether silicone or a leak is involved. Ask them to check the cause, not only to repaint. A whole ceiling, or mould that is making someone ill, is their inspection. Do not accept "just condensation" if nobody has looked for a leak.

Related pages

Mildew treatment comparison

How to use mildew treatment

Best mildew treatment

Mildew treatment buying guide

Mildew treatment before painting: rinse, dry, coat

Sources

Public sources from the research digest, last checked on 22 October 2026. Shelf prices and star lines are the amazon.co.uk figures stored on 19 October 2026. The price band is this set, not a market average. No listing was lab-tested.

  1. GOV.UK: damp and mould, health risks for rented housing (retrieved 22 October 2026)
  2. GOV.UK: Awaab’s Law guidance for tenants in social housing (retrieved 22 October 2026)
  3. The Hazards in Social Housing (Prescribed Requirements) (England) Regulations 2025 (retrieved 22 October 2026)
  4. GOV.UK: damp and mould in the private rented sector (retrieved 22 October 2026)
  5. Bartoline Fungicidal Wash (retrieved 22 October 2026)
  6. Dulux Weathershield Fungicidal Wash (retrieved 22 October 2026)
  7. Dulux Trade Paint Expert: general FAQs (retrieved 22 October 2026)
  8. Healthy Homes: damp and mould guide (retrieved 22 October 2026)