Mould On Brick Veneer Walls: What Causes Condensation And How To Fix It?

Mould on a brick veneer wall almost always points to condensation. Moist air builds up inside from showers, cooking, laundry, and normal day-to-day living.

When that air hits a brick-faced surface that stays colder than the rest of the room, water forms on the wall. Give that damp patch a bit of time, and the black spotting follows.

Brick veneer and thin brick can make this worse because the surface temperature drops fast in cold weather, and the coldest points tend to sit in the same places every time.

Window reveals, corners, and the space behind a sofa or wardrobe get less airflow, so moisture lingers, and the mould gets a head start.

The rest of this guide shows how to spot the exact trigger in your home and what changes actually reduce condensation on brick veneer walls.

Why Mould Shows Up On Brick Veneer Walls?

Mould shows up because a brick faced surface keeps getting wet, then drying, then getting wet again. Condensation drives that cycle in a lot of homes.

Warm air in a room holds water vapour. Shower steam, cooking steam, and laundry drying indoors raise moisture levels fast.

When that warm, damp air hits a colder brick veneer surface, water forms on the face of the wall.

Brick veneer and thin brick tend to run colder than plasterboard walls, so condensation chooses them first, mainly during cold weather and overnight.

Places where mould usually starts on brick veneer:

• Window reveals and the strip of wall beside the frames

• External corners and chimney breasts

• Behind sofas, wardrobes, headboards, or curtains that sit close to the wall

• Areas with a cold patch from insulation gaps or a thermal bridge

• Sections of the wall that stay shaded and do not get much airflow

Home activities that commonly spike indoor moisture:

• Showers or baths without an extractor fan running long enough

• Cooking with lids off, oven door left open for heat, or no kitchen extraction

• Laundry drying on racks indoors

• Lots of people in one room for hours

• Portable gas heaters are used indoors

How To Check If Condensation Causes It

Start with timing and pattern. Condensation mould follows routines. Leaks behave differently.

Signs Pointing To Condensation

• Spots grow after cold nights, then look lighter later in the day.

• Mould appears as scattered black dots, often on the coldest parts of the room.

• Water beads show up on windows, then mould appears near the same area.

• Problem areas sit behind furniture, in corners, or near window reveals.

• The room feels stuffy in the morning, or there is a damp smell that fades after airing out.

Signs Pointing To A Leak Or External Water Getting In

• A damp patch grows after rain, mainly on an outside-facing wall.

• Staining looks like a single patch with a clear edge, sometimes yellow or brown, not just black speckling.

• Plaster blisters, paint peels, or salt marks appear.

• Patch stays wet even during warm, dry weather.

• One spot stays bad while the rest of the room stays fine.

How to be Sure?

• Wipe test: wipe the area in the morning. If the cloth feels wet and the wall looks darker again the next morning, condensation is likely.

• Window check: if windows get wet inside, humidity runs high. Brick veneer surfaces in the same room usually collect moisture, too.

• Airflow check: pull furniture 10 cm away from the wall for a week. If mould slows down there, trapped air played a role.

• Humidity meter: if readings sit above 60 percent for long stretches, mould risk climbs, especially on cold walls.

If the damp comes from contaminated water, wastewater, or flooding, cleaning becomes a different job and usually needs professional help.

What Cuts Condensation On Brick Walls

Condensation drops when two things change: less moisture in the air and warmer wall surfaces.

Both matter. One without the other rarely holds.

1. Remove Steam At The Source

Run the bathroom extractor during showers and keep it running after. Use the kitchen extractor every time cooking starts, especially when boiling and frying.

Steam that stays in a room usually ends up as water on the coldest surface.

2. Keep Wall Surfaces Warmer

Short heating bursts often leave brick walls cold for long stretches. A steadier heating pattern keeps surface temperatures closer to room air, so water stays in the air instead of forming on the wall.

A simple check helps: if a brick wall feels cold to the hand while the room feels warm, condensation risk rises.

3. Give The Wall Breathing Space

Pull sofas, wardrobes, beds, and headboards away from brick walls. Curtains that sit tight to the wall also trap cool air.

A small gap helps airflow and drying.

4. Reduce Indoor Moisture Production

Put lids on pans. Keep bathroom doors shut during showers, then vent the room. Avoid drying laundry on racks in living rooms and bedrooms.

If indoor drying is the only option, use one room with a closed door and active ventilation.

5. Use Measurement To Keep Control

A hygrometer helps track humidity in the rooms where mould starts. Aim for 40 to 60 percent relative humidity.

Levels above 60 percent for long periods support mould growth, especially on cold surfaces.

6. Use A Dehumidifier The Right Way

A dehumidifier helps when ventilation and heating improvements still leave humidity high. Keep doors and windows closed in the room while it runs.

Set a target under 60 percent if the unit allows it. On warm, dry days, open windows can do the same job.

7. Stop The Return Cycle

Cleaning removes visible mould, yet condensation brings it back when moisture keeps landing on the same cold patch.

The steps above work best as a package: source control, extraction, airflow, and warmer surfaces.

How To Clean It And Stop It From Returning

Cleaning mould only works when moisture stops feeding the wall. Without that change, mould comes back in the same spots, no matter how strong the cleaner feels.

How To Clean Mould On Brick And Grout

A person wearing yellow gloves uses a spray bottle to clean a brick wall, with sunlight highlighting the mist in the air

Wear gloves and keep the room ventilated. Use a mould cleaner or a diluted bleach solution. Apply it to the visible area and a wider zone around it, because spores spread beyond what you see.

Let it dry fully before wiping or brushing. Brick and grout can take a bit more scrubbing than painted plaster, but avoid soaking the wall.

Soft finishes behave differently. Wallpaper, fabric-backed wall coverings, and soft furnishings next to the wall often hold spores deep inside. When mould keeps returning on those, removal works better than repeated cleaning.

What Not To Do

Do not paint or seal over mould. That traps moisture and pushes the problem sideways. Do not rely on scented sprays or wipes. They hide smell and colour without touching the cause. Do not scrub dry mould without ventilation, because spores spread into the room air.

How To Stop It From Coming Back

After cleaning, watch the wall. If spots reappear in the same places, moisture still lands there. Focus on extraction during showers and cooking, keep some heat on the wall, and maintain airflow around brick-faced areas. Check humidity during cold weather and mornings, not just during the day.

When cleaning and moisture control work together, brick veneer walls dry faster, and mould loses the conditions it needs to return.

The Bottom Line

Mould on brick veneer walls rarely comes down to dirt or bad cleaning. Water keeps landing on the same cold surface. Until that stops, mould stays part of the room.

Brick veneer and thin brick show the problem clearly because condensation forms on colder wall faces, especially on external walls, corners, and areas with poor airflow. Cleaning helps only when the moisture stops feeding those spots.

Cut moisture where it starts, move steam out fast, keep some heat on the wall, and let air reach the brick surface. Do those things together, and the wall dries. Once the wall stays dry, mould loses its foothold.