Dark spots in the corners, a musty smell, condensation on the windows — none of this is accidental. Mould and moisture always have a specific cause, and until that cause is addressed, any surface treatment is only a temporary fix. Here is what is actually going on.
The Most Common Causes of Moisture in a Flat
In most Warsaw flats, excess moisture comes from one or more of the following sources:
- Condensation — steam from cooking, showers, and drying laundry settles on cold surfaces. Without adequate ventilation, there is nowhere for the moisture to go.
- Thermal bridges — points where insulation is weaker (corners, panel joints, window surrounds). The wall is colder there, so condensation and then mould form first in those spots.
- External leaks, a damaged roof, cracks in the facade, or blocked gutters. Water slowly penetrates the walls from outside.
- Rising damp — common in older buildings without a horizontal damp-proof course. Groundwater literally wicks up through the masonry.
- Pipe leaks, a hidden leak under the floor or behind a wall. Residents often only notice when the stain has already spread.
Why Does Mould Grow So Fast?
Mould is a fungus. It needs humidity above 70% and a temperature between 5°C and 35°C — exactly what most flats offer throughout winter. Mould spores are always present in the air. The moment they land on a damp surface, they begin to grow. A colony can establish itself within 24 to 48 hours of a surface becoming wet.
The highest-risk spots: the bathroom (behind the bath, under the sink), kitchen (above the window, behind the fridge), bedroom (corners against external walls), and storage rooms or wardrobes without ventilation.
How Do You Know What the Cause Is?
The mould on the wall is a symptom, not the problem itself. The real cause is somewhere deeper. Self-diagnosis can be misleading — the same stain can indicate a thermal bridge, a leak from above, or a damaged pipe. Getting the diagnosis wrong means wasted money on repairs, and the mould comes back.
If you are unsure what is causing the problem in your flat, describe it in the app. A handyman will check it on site and suggest a concrete fix. Handymen on the platform work across Warsaw.
When Is This Not a DIY Job?
If the source of damp is a damaged water or drainage pipe, do not put off calling a professional. A leak inside a concealed pipe run can damage the building structure and cause problems for the flat below. The longer you wait, the more expensive the repair.
The cost of the work depends on the nature and scope of the problem — the price list gives ranges, and the handyman names the exact amount after seeing the problem on site.
What to Do Right Now
- Identify the source: condensation, an external leak, or a pipe fault.
- Check the ventilation — are the grilles clear, is the extractor working?
- Inspect window seals — especially important in winter.
- If mould has come back after treatment, look for the cause, not just the symptom.
- If you suspect a plumbing fault, call a professional without delay.
Steam hanging around in the bathroom? How an extractor fan gets fitted is covered in the article on bathroom fan installation. Describe the job in the app and handymen will send you their offers.