vinegar, bleach and clove oil..

you'd need to seal the leaks ..waterproof no point treating the mould and not the source it will come back

Show us the whole wall. Need to see if any bubbling or peeling.

oskuee 8 years ? that's a long time how come so long ? I'm trying to get rid of ours in our holidays house

It's very helpful you shared that, Oskuee.

Hi Cathy, it's really hard to comment on the cause of your mould without knowing more about your house. Are you in NZ or Australia? What's your sub-floor ventilation like?
Assuming you've looked for all the obvious sources of damp - failed gutterings, leaks, etc, then the problem is more systemic.
If you're on a concrete pad, I suspect its damp-proof course has failed, the damp is coming up from below, and there is no easy or cheap solution to the mould.
If you're not on a concrete pad, start at the bottom and work up. Starting at the bottom means putting black polythene on the ground underneath the house. Then check it after the next heavy rain to make sure there's no water pooling anywhere. If there is, figure out where it's coming from and ideally prevent entry, but if you can't prevent entry, work out a way to drain it so it goes out again quickly.
After you've done the polythene, insulate your underfloor. Convention is to recommend insulating the ceiling first, and normally I would, but because your damp starts low down I think your insulation needs to start low down.
Next, insulate your ceiling.
After that, consider what heating and ventilation you have. Damp (and consequently mould) appears when you're not removing water from your house effectively. Water needs to be warm to be airborne to be removed from a house, and you need to have air exchange for the moisture in the indoor air to go outside. So work out the best way for you to heat your house.
As far as wall insulation goes. there are forms of insulation that can be pumped in from the outside. I wouldn't recommend Airfoam unless you're planning to not live in the house for six months after insulation, as it off-gasses undesirable levels of formaldehyde for about that long. After that it reverts to normal background levels. I *think* you can now get rockwool or polystyrene beads pumped in, but I'm not sure how they perform.
However, I would really recommend taking off the gypsum, insulating from the inside and replacing the gypsum, for two reasons: 1. You will have a much better range of insulation options; and 2. Your gypsum walls will have mould growing within their plaster. Even if you dry the room out and prevent more mould growing, all the vinegar in the world will not remove the deep-in mould, and the room will continue to smell of mould for a very very long time, or until you replace the walls.
That's my two cents worth. If you provide more details of whereabouts in which country you are, and what your building materials are, some more detailed advice will be forthcoming :-)

In my old house, we had mold like this in the basement. Not as extreme as your but I treated it with bleach... and after it was all gone I installed a dehumidifier and emptied out almost a gallon per day! That's how humid the room was. It fixed the problem. Good luck, I hope you remove it. I know how hazardous it can be.

Are you renting or owning? What is your nearest large town or city?

I'm trying to look for pros for you, but need approx location.

Damprid would be useful as part of identifying the source of the problem, but is unlikely to be an effective solution long-term, as it addresses the symptom rather than the cause.

I've found the only way to stop the windows condensing is to leave them open a tiny fraction overnight to get some air flow, then leave them open wider all day when we are not at home. It does mean it is cold when you return home- but dry none-the-less and no mould.

Given you are on a slab, perhaps go around and get rid of any garden growing up against the house. If you are really keen- dig out the sides of the house to form a trench all the way around. Lay some ag-line then backfill it with blue metal. You've really got to focus on getting water away from the house and slab. Definitely get all your gutters and downpipes checked too....again to get all the water away from the house. If you live in an area with lots of clay- be aware that your slab might be drawing moisture up from the ground and there is no way you can stop that.....you just need loads of ventilation (open window and extraction fans) and get all other water you have control of (roof and garden) away!

If you want a less intrusive alternative to bubble wrap on the windows, I recommend the 3M window insulation film (https://www.bunnings.co.nz/3m-window-insulator-kit-5-windows_p00167658 in NZ, not sure about availability in Aus). We used it in our south-facing bedrooms until the double-glazing was installed.

Since you are on a concrete slab, and that's an invasive/expensive fix, you probably want to check all other possible solutions first. You could try digging a ditch around your house to reduce moisture penetration into the slab?

Unfortunately, if you have rising damp, heating the room can make the problem worse, as a warm room will draw the moisture out of the ground beneath.

We installed a heat transfer system in our last home and now in our current home, it helps remove condensation and also warms the air using the heat from the roof space when the sun is shining, it fixed the mould in our last home and i hope it does this time round too.

Definitely call in an expert to find the source of the problem.

Never compromise your health - that mould has to go completely. Find the cause. Ours was water pooling under the house, and leaky gutters. We lived in a high rainfall, lots of fog area.Thank God we've moved! Replace the mouldy wall linings, you'll have to redecorate anyway, and your lovely room will be healthy and will stay looking fresh and smelling nice. We also installed a heat transfer from the ceiling, with outlets in the bedrooms and living room. Damp carpet and crying windows fixed! Made a huge difference, no more mould in the wardrobes. Best of luck.

You need to urgently hire some professionals because that amount of mould "black mould" has very had effects on your health. You will likely need to spend some money but it will be money well spent. Put your health needs first. You should not be living with that mould in your house - black mould is a killer.

Hi Cathy,
For improving your window condensation problem and preventing conditions that mould thrives in, we would recommend awning windows as they seal properly at night and then can allow constant airflow during the day as they can be left slightly open all day and locked. A better performing glass like Low-E Smartglass would also help improve insulation of the windows.

Gyprock has a mould amd moisture resistant plasterboard that might be suitable for your areas. It is the only residential platerboard approved by the National Asthma Council of Australia's Sensitive Choice program. http://www.gyprock.com.au/Pages/Products/Plasterboard/Sensitive.aspx

HI All....read everything and to me it would appear the main cause is your slab, albeit issues around the slab.

A trench is a start, with extra drainage (black round pipe with heaps of holes in it, and loads of scoria). My opinion is that the actual ground is damp and unfortunately concrete is porous, so as long as there's heaps of water around that cannot drain away, the concrete will slurp it up. (I'm no drainage expert)

As far as your gib goes, I don't think you have any option but to replace it (then insulate wall by wall as you go.)

Here in NZ, I previously worked for a company that did leaky building repairs, and honestly, that black mould is a very real danger to the family's health, so it's got to go. Like others have said, you may get rid of it visually for a period of time, but once you rip the gib off, you may come across other issues.

I'd also invest in a dehumdifier and keep that cranked to start getting moisture out of the air, or other options as others have mentioned.

Sorry Cathy, ain't no easy fix there.....................

Is it possible to have a look into council records to see what the land back in the day was actually used for? That may give you an insight into what the problem could be.

Hi Cathy, I'm a Mould Professional www.mouldrescue.com.au. There are a number of things that need to happen, first of which is a thorough assessment to determine the exact cause. From the look of the picture it seems there is water ingress from somewhere and without doubt there will be mould underneath the carpet and inside the wall cavity. Feel free to call me to discuss 0425 044 501