how to rectify mouldy ceilings??

[wozzzzza]

got ceilings in units that are getting mouldy for really no apparent reason apart from being Cairns and humid here. no leaks or anything, they are all doing it in varying degrees, haven't been painted for 25 years either and original paint.
the mould is uniform all over the ceilings, not in one area and not that bad.
what is the best way to repaint these ceilings to stop the mould coming through again?

[419]

The first thing is to identify the type of mould. Some moulds are quite dangerous to health including those trying to remove it, others aren't. Some are fairly easy to remove permanently with readily available treatments such as vinegar, others aren't. And so on.

The next thing is to identify the cause and or source of the mould, which could include ventilation, drainage and damp issues.

The next thing is to identify the best coating to put on the surface after the mould is removed.

Get a local mould specialist to inspect and advise so that you know what you're dealing with and get the correct advice on how to proceed. It'll probably work out a lot cheaper, better and more durable to get specific expert advice and do it once and do it properly.

Or, on the cheery 'have a go anyway' side, you could just spray everything with mould killer; neutralise it; and coat with mould resistant paint and hope that you haven't inhaled really bad mould spores in the process. And that if the units are tenanted, your insurer will cover you for any injury to the tenants.

[419]

P.S.

I had to miss a lunch today with a mate because I can't shake the final stages of a mild respiratory bug.

My mate has a longstanding and still not adequately diagnosed or treated but possibly tropical mould related lung illness from his time as a soldier in Vietnam in the 1970s. What's a mild bug for me could be the final bug for him.

Mould illnesses are generally misunderstood and underrated, except by those unfortunate enough to experience the really bad and persistent ones.

It's not worth the risk of doing amateur work with mould.

[Beardy]

I did a commercial kitchen reno with a mould issue from long term leaks
They engaged a mould specialist to treat and sign off the area as being safe. I haven’t tried it but he said the only oroduct from Bunnings that works to kill mould is Concrobian

Just a moment... (https://www.bunnings.com.au/concrobium-946ml-mould-cleaner_p4460772)

[Mobyturns]

Mold or mildew? Mildew is considered to be "flat" with no fluffy bits above the surface and generally not as worrisome as molds.

Mold is common on both Gyprock and AC sheet ceilings in the tropics. On AC sheet ceilings it tends to form more between the battens so visible alternating bands are very apparent. It seems the unsealed upper surface takes in moisture, promoting mold growth.

A trick many professional / commercial cleaners use to fix mildew on ceilings in the tropics is to mix SnowWhite with regular plain dish washing detergent place into a pressure spray pack then liberally spray onto the ceiling. Let sit for half an hour or so then wash / lightly scrub down with a soft broom and clean water, changing the water regularly. It works well, however if you don't wash it down sufficiently well the bleach tends to rust nails, screws etc.

Be Warned - You take your chances with Gyprock though!!!!