Child Item

How to remove mould underneath carpet?

Hey folks,

We found out just yesterday that water was leaking through the cracked grout on the shower and the water was reaching to the next bedroom. I only found out yesterday and it seems like it has been happening for a while. I could feel the carpet wet around some area. when lifted the carpet, I could see Black Moulds.

When I read about them, they are hazardous.

Is there some precaution I can follow to remove them myself? I read that floor treatment is needed in such case ? What chemicals are used ?I will be changing the carpet and water has eaten the stick that holds the carpet or lies beneath the skirting?

or should I be living this to professional

Thanks

Find more posts tagged with

Tools and Materials

Repairing

Flooring

Cleaning

Accepted answers

All comments

EricL

Hi @Sugar

I'm sorry to hear you've got a leak in your shower. When water leaks through cracked grout in a shower, it doesn’t just stay on the surface. Moisture seeps into the wall cavity, soaking the framing, insulation, and plasterboard or fibre cement backing. Over time, timber can swell, soften, or even rot. Insulation may become waterlogged, and mould can grow behind the walls where it’s not immediately visible. The tiles themselves might also become loose if the adhesive weakens.

The leak won’t be contained to the bathroom—it can spread under the skirting and into adjoining rooms. Lifting the carpet and underlay might reveal black mould, rotting carpet tack strips, and swollen skirting boards. If the subfloor is particleboard, prolonged exposure to moisture can weaken it.

Cracked grout allows water to bypass the waterproofing layer. If the waterproofing has failed, resealing the grout alone won’t stop the leak, and water will continue to spread beneath the tiles. In severe cases, moisture damage can extend beyond the immediate area, requiring more extensive repairs.

Since the full extent of the damage isn’t visible until things are opened up, it’s best to bring in a professional for a repair quote. They can assess how far the moisture has spread, whether structural repairs are needed, and if the waterproofing in the shower needs to be redone to prevent future leaks.

While waiting for a professional assessment, treating the mould in the room with a 1:1 vinegar and water solution is a good first step. Vinegar kills mould spores and helps prevent regrowth, but make sure to wear gloves, an N95 or P2 mask, and keep the area well-ventilated to avoid inhaling airborne spores.

For the wet, mouldy carpet, it’s best to remove it as soon as possible. Leaving it in place can trap moisture and allow mould to spread further. If the damage is only in a small section and the underlay is still dry, you might be able to cut out the affected area, treat the subfloor with vinegar or a mould killer like Concrobium from Bunnings, and let everything dry thoroughly before replacing that section. However, if the carpet and underlay are both soaked, they will likely need to be fully removed and disposed of, as mould can grow deep within the fibres.

If you have any other questions we can help with, please let us know.

Eric

Sugar

Hi @EricL

All the possibilities you have said are totally understandable. I had one tradie coming in and had inspection. His words were same.

The house is on slab. I am going to remove the whole carpet, remove the skirting board with fresh board, do the floor treatment for the moulds.

The house was built in 1993. One of the tradie said, there was no waterproofing things back then (new thing for me, if this is true). if so, you may be right on saying that only the ground wouln't be possible to hold the water. Tradie said you need to tear apart the plasterboard along the floors and investigate further.

The professional guy also said the black mould underneath the carpet are dangerous. They have to be handled with property PPE suits, gloves, mask etc. (every possible PPE we could get). I am going to tear those carpet as well. Where do we dispose them after pulling out ?

Please give me details if there are anything I need to be careful PPE wise.

The damaged are where the red rectangle is, and may/may not have already moved to green line. No idea about inside.

I am not sure what should be the right sequence. I would like to get Building and Pest Inspection person and have a look at the whole house ( and this problem as well)

B& P was done in 2019 and not since then. I think it is already due. How long house like mine should have B&P inspected ?

1.) Remove the Carpet

2.) B&P Inspection or Bathroom Renovation

If the bathroom renovation is done and I get B&P person later, they may not have full visibility of what's inside the plasterboard where this leakage is happening unless the bathroom renovator has details about damages.

First time I am having professional to do something in my house.

What certificate I should be asking if they comply with them, like QBCC, waterproofing etc.. Not that I don't trust them, but for my sake also. I think knowing what they are certified for is the way to go.

Thanks

MitchellMc

Hi @Sugar,

It sounds like you're dealing with a significant issue, so it's great that you're being proactive in taking steps to manage the situation.

When dealing with mould, it's important to use proper PPE to minimise exposure to hazardous mould spores. You should wear an N95 or P2 respirator mask, gloves, and protective eyewear. If you can, consider wearing disposable coveralls to avoid contact with mould spores on your clothing. Make sure the area is well-ventilated, and if you're working in a confined space, use a fan to direct airflow outside to reduce the chances of inhaling spores. Also, remember to wash your hands and clothes thoroughly after handling any mouldy materials.

For the disposal of the carpet, you should check with your local council, as many councils provide specific guidelines for disposing of hazardous waste like mould-affected materials. It’s important to not just throw it in regular rubbish, as it can spread spores. Some areas might offer specific disposal options for contaminated items, or you might need to take it to a waste management facility that handles this kind of material.

Your sequence for repairs sounds reasonable. If you’re concerned about hidden damage within the walls, I would recommend starting with the Building and Pest (B&P) inspection before you begin the bathroom renovations. The B&P inspector can help identify areas of concern you might miss, including moisture issues inside the walls. Once the full extent of the damage is assessed, you can decide on the next steps for the bathroom renovation. It’s important to understand the full scope of the problem to prevent issues from worsening once repairs are done.

Regarding certificates, it’s definitely a good idea to request proof of the contractor's qualifications and certifications, such as a QBCC licence (Queensland Building and Construction Commission) if you're in Queensland or a similar regulatory body for your area. You’ll also want to ensure the bathroom renovator is qualified for waterproofing work, and they should be able to provide a warranty for their work. Make sure they follow the correct industry standards and regulations for mould remediation and waterproofing.

Please let me know if you have any questions.

Mitchell

Sugar

@MitchellMc @EricL

I just realised that I had forgotten to paste the picture of my bathroom and room where I think the damage is.

Red line, where I think the grout cracks were and where the leakage happened.

Green rectangle is where the wet carpet is. The moisture may or may not have reached along the wall.

I got renovator coming in, the charge is high, I am being honest here , 15K-25K, and I don't doubt about their skills.

I am thinking if there are anyhing that I can do/chip in to minimize the cost, please help me guys, what I can do there.

1.) Demolition, taking tile out, taking vanity out, taking shower screen out, taking bath tub out.- pretty much taking everything out and making a big canvas for them.

Image (25).png worried me :) worried me 🙂 Image (23).png Image (14).jpg

2.) What I need to be carefull and tools I need for demolition. I think I will need skip. Is this somethign I can do, if not in rush?

3.) Get the tiler/plumber when the righ times come in to install them

4.) May be ripping off the bathroom walls, whichever is need to take down. I guess no insect or anything come from skeleton frames

Sugar

@MitchellMc @EricL

Not to forgot the carpet laying on another room and removing the old, mouldy carpet.

EricL

Hello @Sugar

I suggest speaking to your builder in regards to the type of work that needs doing and which parts can be done by yourself or if there is any prep work you can do for them.

If you need further assistance, please let us know.

Eric

Child Item