What Causes Carpet Mould and How Do You Treat It?

Carpet mould is all too common, especially in humid areas like Queensland. All it takes is a leak, a moisture problem, or an intense storm and the process begins. In extreme cases it can spread throughout a whole room, but often it’s contained to a corner, a small section along a wall, or in a bathroom doorway. So what can you do?

Working With Mould Remediation Specialists

First, an important note: Express Carpet Repairs aren’t a mould remediation company, and we don’t claim to be. What we cover is the removal of carpet around the affected area, and the reinstallation afterward.

It’s best to call in mould remediation specialists before we come in. Most times they’ll remove any carpet, edging, or underlay that’s been affected by mould. The issue is that they aren’t carpet specialists, so their removal can be quite rough — non-straight or diagonal cuts — which makes the patching process more difficult for us. That’s why it’s best we work in collaboration with the remediators, ideally having the area marked out for us to come in and cut cleanly.

How Carpet Type Affects Mould Growth

Carpet type has a lot to do with how badly mould affects your carpet. Natural fibres like wool tend to get mould the worst. Wool is an organic fibre, making it a prime environment for mould, which survives off organic material. It also retains moisture extremely well, which only adds to the issue. (moths also love it, see Carpet Moth Damage: Repair And Prevention)

Nylon, polyester, and polypropylene are a step down. The fibres themselves ward off growth because they’re synthetic — mould can’t grow on what’s essentially plastic. The only issue is the backing, or more specifically the latex that holds the backing to the fibre. Latex is an organic material, so synthetic carpets still have some conditions for mould growth.

If you were to order them from highest to lowest resistance, it would start with polypropylene (which doesn’t retain moisture as well), then polyester, then nylon. This is essentially in order of moisture retention.

Underlay, Smooth Edge, and Subfloor

The next factor is underlay. Most underlay is made from foam and plastic, so the same logic applies as the carpet. Foam holds moisture well, which can help mould grow around the area. Any organic underlay (wool, cotton, etc.) provides another good environment for mould growth.

Then there’s smooth edge — the wooden edging that goes around the perimeter of a room, underneath the carpet. Because it’s made of wood, it’s usually the main driver of mould growth and spreading, since it follows the entire perimeter of the room.

Finally, the subfloor — what sits underneath your carpet and underlay. A concrete subfloor can contribute like the others due to moisture retention, with mould surviving off any dirt or debris in the area. But it’s not a direct host to mould like wood. Wooden or chipboard subfloors are the worst for mould growth because the mould feeds directly off them, which can eventually rot the area and cause structural damage.

What Mould Actually Feeds On

Carpet, synthetic underlay, and concrete usually aren’t the real problem. They only contribute by holding moisture, which helps the mould reach the organic materials around them. Any dirt or debris trapped in the carpet, underlay, or on top of the concrete gives the mould something to feed on. But when it comes to the wooden edging or subfloor, that’s the worst — because the mould directly eats it. Concrete, on the other hand, is manageable and usually cleanable.

How to Tell If You Have Carpet Mould

Usually the first sign is the smell. In more extreme cases, when the smooth edge has fully rotted, the carpet will begin letting go (since smooth edge is what holds it in place). It’ll become loose and start lifting in the area(Also see When Do You Need Carpet Stretching?). You may also notice discolouration or visible mould around the edges or even on top of the carpet.

How We Fix It

Smooth edge: This is the easiest to replace and is usually the most affected by mould and rot(see Smooth Edge Installation)

Carpet: Sometimes, if the mould has been growing for a long time, the affected area will need to be cut out and patched with a new piece(see Carpet Patching)— usually sourced from a wardrobe(See Donor Carpet & Wardrobes)

Underlay: This can also be replaced if needed, just in the section that’s been affected(see Underlay Replacement)

Here’s a video of the process:

Any issues with the subfloor are beyond our wheelhouse, but we can do a general inspection and open up the area to allow for professional work or a deeper inspection.

Get Your Carpet Mould Repaired

If you’re having carpet mould issues, or even just unsure about an area due to smells or discolouration, we can take a look and fix any issues or put you in the right direction for next steps, just give us a call. We work all throughout Brisbane, Gold Coast, and Sunshine Coast.