WOLLONGONG MOULD REMOVAL SERVICES
Wall Mould Removal in Wollongong
A wall only has to sit about two and a half degrees cooler than the room before mould can start growing on it. It never has to get wet.
Trusted Wall Mould Removal Specialists
You pulled the bed away from the wall to vacuum and there it was. A grey bloom across the bottom corner, maybe up behind the bedhead, and the paint underneath feels cold and slightly chalky. You wiped it. It came back within a fortnight. Nobody in the house can work out where the water is coming from, because there is no leak, no burst pipe, nothing above it, and the rest of the room is dry.
That is the most common wall mould job we see, and the reason it confuses people is that everyone is looking for water. There usually isn’t any.
Wollongong Mould Cleaning & Removal has been working on mould and water damage across the Illawarra for 15 years, from the escarpment suburbs like Keiraville, Figtree and Mount Ousley through to Corrimal, Fairy Meadow, Woonona, Warrawong and the northern beaches. Same team diagnoses the wall and fixes it. You deal with one person start to finish.
Situation sound familiar?
- Mould appears on the same wall every winter and clears up over summer
- It is worst behind the wardrobe, the bedhead, the lounge or a stack of boxes
- The affected wall is a south-facing or south-east external wall
- It sits low on the wall, in the corner, or in a band near the skirting
- You have wiped it with vinegar or bleach and it returned within weeks
- Your dehumidifier or hygrometer reads a normal 55 to 60 per cent and you cannot understand why there is mould at all
We will come out, read the wall properly with a moisture meter and a surface thermometer, and tell you what is actually causing it. The inspection costs nothing.
FREE ASSESSMENT, NO OBLIGATION
We will call you back personally to arrange a time.
Cold Wall or Rising Damp, Which One Do You Have?
There are two very different problems that both show up as mould on a wall, and they need opposite fixes.
Cold wall condensation comes from the room. Warm damp indoor air meets a wall surface that is cooler than the rest of the room, the humidity right at that surface climbs, and mould starts. It shows up as a soft-edged patch or speckle, it is worse in winter, it is worse behind furniture, and the wall itself will usually read dry on a moisture meter even while mould is growing on it. That is the job this page covers.
Rising damp comes from the ground. Groundwater wicks up through brick or stone and evaporates out of the wall, so it shows as a hard-edged tide mark at a fairly constant height above the floor, often with salt crystals or bubbling paint, and it is there all year. NSW Health describes the fix as a new damp course or waterproof barrier in the wall, plus keeping weep holes and subfloor vents clear, which is a different trade to a wall clean. If the trouble is coming up out of the ground rather than out of the room air, the wall has to be treated at its base, and that is covered on our rising damp treatment page.
Two more worth ruling out. If the mould starts up at the cornice and runs along it, or spreads out from a point on the ceiling, the cause is above you rather than beside you, and ceiling mould is the page that walks through it. If it is confined to the bathroom walls and grout, the moisture load is coming off the shower, and bathroom mould removal deals with the fan and venting side of it.
If you have more than one of these at once, or you are not sure which you are looking at, start at our mould cleaning hub and we will sort out which job it is when we inspect.
How We Remove Mould From Walls As Specialists
We read the wall before we touch it
Moisture meter across the affected area and the surrounding wall, plus a surface temperature reading on the mouldy patch and on an internal wall in the same room. The difference between those two numbers is usually the whole answer. We also check what is on the other side of that wall, because a wardrobe in the next room, an unlined garage or an unventilated cavity changes the picture.
We contain the area and protect what is near it
Sheeting on the floor, furniture moved out or covered, and HEPA extraction where the growth is heavy. Dry brushing or sanding mould off plasterboard without containment puts spores through the rest of the house, which is the fastest way to turn a one-wall job into a four-room job.
We treat the growth at the surface and into the paint film
Painted plasterboard is only semi-porous, so on most walls the growth sits in and just under the paint film. We clean it out rather than bleaching the colour off it. Where the mould has gone through into the paper face of the plasterboard, cleaning will not hold and we will tell you that on the day rather than after you have paid for a clean.
We close the temperature gap that caused it
This is the part that decides whether it comes back. Depending on the wall, that can mean airflow behind furniture, ventilation, a heating pattern change, insulation, or a dehumidifier run to a measured target. If the wall needs work behind the lining, that is a plasterboard replacement job and we will price it separately so you can see what you are paying for.
We come back and check it
We take a second set of readings once the room has been through a normal week. If the surface temperature gap has closed, the wall stays clean.
Your Wall Does Not Have To Be Wet To Grow Mould
Nearly everyone assumes the wall must be damp. It is the single most common misunderstanding about internal wall mould, and it is why people keep looking for a leak that does not exist.
Here is the actual mechanism, and you can check the numbers yourself.
The Australian Building Codes Board publishes a handbook called Condensation in Buildings. It sets out the conditions mould needs on a building surface:
- Spores present
- Something to eat
- Temperature between 4 and 40 degrees, and
- Relative humidity above 70 per cent at the surface. Not in the room. At the surface.
The handbook is blunt about the consequence, saying that unwelcome effects “can emerge before relative humidity reaches 100% and the dew point when condensation begins.”
Run the arithmetic on a normal Wollongong lounge room in July. Say it is sitting at 20 degrees with 60 per cent humidity, which is comfortable and unremarkable.
- For water to actually condense on the wall, that surface has to fall to 12 degrees. Eight degrees colder than the room. That almost never happens on a wall, which is why you never see droplets.
- For the surface to pass 70 per cent humidity and become viable for mould, it only has to fall to 17.5 degrees. Two and a half degrees colder than the room.
We can agree that 2.5 degrees is nothing. That is the difference between an external brick wall and an internal one. It is the difference between the face of a wall and the strip of it hidden behind a wardrobe. The Codes Board handbook says exactly that, noting that surfaces “inside cupboards and behind or under furniture that limit the circulation of warmed air” are at risk, and that wall corners and the framing around window and door openings are worse again because the framing crowds out the insulation.
Even on the more conservative 80 per cent surface figure used in current moisture modelling, that wall only has to be about four and a half degrees cooler than the room. Still nowhere near wet.
So when someone tells you the wall is dry so it cannot be a moisture problem, they are measuring the wrong thing. A moisture meter reads water inside the material. Mould responds to humidity sitting on top of it. On a cold wall those two numbers disagree, and the mould goes with the surface.
This is also why we will sometimes tell you not to hire us – you may not need it. If your patch is small, on painted plasterboard, and it turns out to be a two-degree problem, then pulling the wardrobe 50 to 75mm off the wall so air can move behind it, running the heater a bit longer, and cleaning the patch with NSW Health’s recommended four parts vinegar to one part water will fix it. If it wipes off and stays gone through a full winter, you have just done the job yourself and saved several hundred dollars. Do that first. Call us when it comes back, when it is spreading, or when the wall reads wet as well as cold, because that means something else is going on behind it.
Bedroom, Wardrobe and Living Room Wall Mould
Walls are rarely the only surface involved, and the room usually tells you what else needs looking at.
- Wardrobes and built-ins are the worst spot in most houses, because the door blocks airflow and the back panel sits against the coldest part of an external wall. Clothes, shoes and leather go mouldy in there before the wall does.
- Where the growth has run up onto the cornice or across the ceiling above, the cause is coming from above and needs the ceiling mould removal approach instead.
- Where it has reached the carpet, underlay or floorboards at the base of the wall, the flooring has to be assessed separately, which is covered under mould on floors.
- Where the growth is heavy, dark and spread across more than a square metre or so of wall, the job stops being a clean and becomes a remediation with containment, and black mould removal explains how we handle it.
- Where the same mould is turning up on multiple walls in a unit or on the vents themselves, the air conditioner or its ducting is often the distribution system, and that is dealt with under air conditioning mould.
Skirting boards, architraves, window reveals and the back of built-in joinery are treated as part of the wall job, not as separate items.
How Much Does Wall Mould Removal Cost?
The on-site inspection is free, and that includes the moisture and surface temperature readings, so you get the diagnosis whether or not you book the work.
| Size of the job | What it covers | Cost |
|---|---|---|
| On-site inspection | Moisture readings, surface temperature comparison, cause identified, written scope | Free |
| Small patch, surface only | One corner or one section of wall on sound painted plasterboard. Often the job you can do yourself. Ask us on the day. | $100 to $300 |
| Full room treatment | All affected walls in one room, wardrobe interior, skirtings and architraves, containment, HEPA extraction, drying to a measured target | $500 to $1,000 |
| Multiple rooms or spread | Several rooms, or a wall where the growth has gone through the lining and sections need cutting out and replacing | $1,000 to $4,000+ |
What moves the price on a wall job is mostly what the wall is made of and how deep the growth has gone.
- Painted plasterboard in good condition cleans up quickly.
- Wallpaper, unsealed render, raw plaster and untreated timber lining are porous, so the growth is inside the material rather than on it, and those usually need removal rather than cleaning.
- Built-in wardrobes add labour because the joinery has to come out to reach the wall behind it.
- Access matters too, and a wall behind a fixed bulkhead or a fitted kitchen costs more than an open bedroom wall.
- The other one that catches people out is scope creep at the skirting. If the growth has run down behind the skirting into the carpet edge or the underlay, that flooring work is priced on top.
These are Illawarra market rates for this kind of work. Your quote after the inspection is the number that counts.
Why Wollongong Walls Grow Mould Where They Do
Once you know it is a two-degree problem rather than a water problem, the pattern across the Illawarra makes sense.
South and south-east walls come first. In the Southern Hemisphere a south-facing wall never takes direct sun, so it runs cooler than every other wall in the house through the whole winter. Under the escarpment it is worse again, because in suburbs like Keiraville, Mount Keira, Mount Ousley, Balgownie and Figtree the ridge takes the afternoon sun off the western side of the house early, and those walls do not get their evening warm-up either.
Then there is the housing stock. A lot of the Illawarra was built between the 1950s and the 1970s, and double brick and early brick veneer from that period usually has nothing in the cavity. An uninsulated external wall tracks the outdoor temperature far more closely than an internal one, which is exactly the temperature gap that gets a surface over the mould threshold. Newer units and townhouses have their own version of it, where a concrete slab edge or a party wall runs cold and the mould turns up in a neat line along it.
Also, indoor humidity sits higher year-round than it does inland, so there is more water vapour in the room air to begin with. That means the wall does not have to get as cold before the surface tips over.
Put those together and you get the layout we see over and over. Coldest wall in the house, furniture pushed against it, curtains closed, door shut, heater off overnight.
Get Your Assessment Today
If the mould is back on the same wall for the second or third winter, wiping it again will not change anything. Have someone read the wall and tell you the actual cause.
The mould inspection is free and you get the readings and the explanation whether or not you book the work.
No obligation, no pressure.
Call Now (02) 4093 0541
Frequently Asked Questions
How much does it cost to remove mould from a wall?
- Between $100 and $300 for a small patch on sound painted plasterboard
- $500 to $1,000 for a full room
- Multi-room jobs or walls where the lining has to come out run from $1,000 to $4,000 and up.
The inspection is free, so you get a firm number before you commit to anything.
Can I remove mould from my walls myself?
Often, yes.
NSW Health recommends mild detergent or a solution of four parts vinegar to one part water for routine clean-up of mouldy surfaces, and on a small patch of painted plasterboard that works.
The catch is that cleaning removes the growth without changing the conditions, so unless you also fix the temperature or airflow problem, it grows back. If the patch is bigger than a sheet of A3, if it is on wallpaper or bare plaster, or if it has come back more than twice, get it looked at.
Why does mould keep coming back on the same wall?
Because the cleaning removed the mould and left the cause. Mould needs about 70 per cent relative humidity at the wall surface, per the Australian Building Codes Board’s Condensation in Buildings handbook, and a wall only has to be a couple of degrees colder than the room to reach that. Until the surface temperature or the airflow changes, the wall stays viable and the mould returns.
Is mould on my bedroom wall dangerous?
Most people have no health effects from contact with mould, according to NSW Health.
People with asthma, allergies or other breathing conditions can be more sensitive, as can people with weakened immune systems. If anyone in the house is unwell and you think mould might be involved, see a doctor. Either way it is worth removing, because mould on a wall is telling you something about moisture in the building.
My walls are dry. How can it be a moisture problem?
A moisture meter measures water held inside the material.
Mould responds to the humidity sitting on the surface of it. On a cold wall those two readings disagree, and the mould follows the surface. A wall can read completely dry and still hold over 70 per cent humidity at its face if it is running a few degrees cooler than the room air.
Is wall mould the landlord's or the tenant's responsibility in NSW?
It depends on the cause, and this is general information rather than advice. Under the NSW Government’s landlord obligations, the property has to be fit to live in and kept in a reasonable state of repair, so mould caused by a building fault such as a leak, a defect or missing ventilation generally sits with the owner. Mould that develops because the property is not being ventilated during the tenancy can sit with the tenant. NSW Health’s position is that if you rent, have ventilated the place properly and the mould is still growing, raise it with the owner or agent, and that tenants can call NSW Fair Trading on 13 32 20 for their rights and responsibilities. A written inspection report showing the cause is usually what settles the argument, and we can provide one.
Will painting over wall mould fix it?
No.
Paint is a food source and a thin one, so the growth comes back through the new coat, usually within a season. Anti-mould paints slow it down but they do not change the surface temperature, which is what created the problem. Clean it out properly, fix the cold spot, then paint.
How long does wall mould removal take?
A single patch is usually an hour or two. A full room with containment and drying is typically one day on site plus a drying period of a few days with equipment running. Jobs where sections of lining have to be cut out and replaced take longer, because the wall has to be dry and confirmed dry before it gets closed up.
Do I have to move out?
For a normal wall job, no.
We contain the work area and use HEPA extraction so the rest of the house stays usable. If the job is large enough to need a full containment across several rooms, we will tell you at the inspection so you can plan around it.