It comes back because the reason it grew is still there. Cleaning fixes the look for a few weeks; fixing the moisture fixes the room.
Bathroom mould keeps coming back because the cause is still there. Usually the room stays humid for too long after a shower or bath, and the ceiling, the outside wall or the window reveal is cold enough for that moisture to settle and stay. Mould grows wherever a surface stays damp for long enough.
Sometimes it is not condensation at all. Mould that spreads from the sealant round a bath or shower tray, or sits on one wall only, can be a sign of water getting behind the tiles.
Mould in the sealant itself often cannot be cleaned out because it grows into the silicone. Cutting the old sealant out, drying the joint and resealing it is usually the answer.
Warm, wet air rises, so the ceiling takes the most moisture, and a bathroom ceiling under the loft is often one of the coldest surfaces in the house. Mould over the shower or along the outside wall usually means not enough extraction, insulation missing above, or both. See black mould on the ceiling.
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Because the room stays damp for long enough after showers for mould to grow, usually on the coldest surfaces. Cleaning removes it, but unless the moisture is extracted and the cold surfaces are dealt with, it returns.
Warm, moist air rises and the ceiling is often one of the coldest surfaces, especially under a loft. Weak extraction, a fan that stops too soon, or missing insulation above all make it worse.
Long enough to clear the steam, which for most bathrooms means at least 15 to 20 minutes after you finish, with the door shut. A fan with an overrun timer or humidity sensor does this for you.
Bleach whitens the stain on the surface but does not change the conditions that let mould grow. On porous surfaces such as plaster, grout and silicone, growth inside the material can survive. If the room stays damp, it comes back.
It can be a sign that water is getting behind the sealant. Mould inside silicone usually cannot be cleaned out, so cut out the old sealant, let the joint dry fully and reseal. If the wall or ceiling nearby is also damp, look for a leak.
No payment to book. Tell me what you are seeing and I will call you straight back, usually within a couple of hours, to arrange a visit and confirm the fixed price.
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