Mould in a rented flat

Who is responsible for what

A dispute about mould in a rented flat is almost always a dispute about the cause. The landlord thinks the tenant does not air the place; the tenant thinks the building is damp. Often both are partly right.

We are not lawyers and we do not give legal assessments. But we can state the technical cause — and in practice that is usually what resolves the dispute, because both sides are looking at the same measurement.

The dispute ends the moment both sides are looking at one measurement rather than one patch.

In practice the situation is rarely clear-cut. The typical picture: a flat in a panel block, an external wall corner in the bedroom with a cold bridge — a structural matter. At the same time laundry is dried in the room and it is never aired — a usage matter. Neither factor alone might have produced the patch. Together they produce it reliably. A measurement shows that, and from there the parties agree who does what.

How the cause looks in each building type

The type of building changes where responsibility most likely sits, because it changes the possible causes.

What the tenant should do

• Photograph the situation as soon as you notice it and note the date.
• Notify the landlord in writing — a message or an e-mail will do. A verbal conversation cannot be evidenced later.
• Do not start painting over it or hiding the problem — that can later be treated as making the situation worse.
• Keep airing normally and, if you can, do not dry laundry indoors — that removes part of the possible objections.
• Measure the humidity with a hygrometer and record the readings with dates.
• Check the extract with a sheet of paper and photograph the result.
• If the landlord does not respond, an independent inspection with readings gives you an objective document.

A record of hygrometer readings with dates is a stronger argument than it seems. If humidity in the room is consistently 45–55% and the patch is still growing, that points to the structure rather than to how the flat is used. If the reading is 75% and laundry is drying in the bedroom, that is visible too, and there is no point running from it — better to change it before the conversation starts.

What the landlord should do

• React quickly — mould that has been growing for months requires a more expensive fix than one that has just appeared.
• Order an inspection with moisture readings before drawing conclusions about the tenant's fault.
• If the cause is the ventilation or the structure, dealing with it is an investment in the property, not an expense.
• After treatment, keep the inspection result — it is useful in the next tenancy cycle.
• Check whether the flat has any air supply at all after the windows were replaced.

One thing landlords are worth knowing: a cold bridge in an external wall corner is a property of the structure, not a consequence of how the tenant behaves. It can be softened with routine — furniture away from the wall, more frequent airing, a warmer room — but it cannot be removed by making demands of a tenant. If the patch comes back every winter in the same corner regardless of who lives in the flat, the answer is in the structure.

When the property manager gets involved

If the cause is in the common parts — a shared ventilation shaft, the roof, the facade, shared pipework, the basement — it is not something the tenant or the individual flat owner can resolve alone. It has to be addressed to the property manager.

In practice that means the inspection result has to be specific enough to submit: where it was measured, what the readings were, and what the conclusion about the cause is.

What to document and how

Most disputes about mould in a tenancy collapse not because either side was in the wrong, but because nobody documented anything. A dated photograph and a couple of readings are more than exists in most cases.

• Photograph the patch from a distance and close up, so that both the size and its place in the room are visible.
• Put a tape measure or an object of known size in the frame — later it will be clear how large it was.
• Mark the edge of the patch with a pencil and the date, so you can see whether it grows.
• Record hygrometer readings over several days, with dates.
• Film the paper test at the ventilation grille.
• Keep correspondence with the landlord or property manager in written form.

A pencil mark with a date is the simplest tool on the whole list and at the same time the most informative. If after a month the patch has crossed the line, the situation is getting worse, and both sides can see that without any interpretation.

At handover

Handing the flat back at the end of a tenancy is a situation of its own. Here the dispute is often about whether the mould was already there when the tenant moved in or appeared during the tenancy, and usually nobody can answer, because nobody documented anything at the start.

The simplest solution for both sides is dated photographic records both on moving in and on moving out, and a note on the condition of the rooms in the handover record. It takes fifteen minutes and removes most of the later dispute.

If the flat is being prepared for a new tenancy cycle, treatment is often combined with ozone treatment of the rooms, to clear any remaining smell from textiles and hard-to-reach places at the same time. That is a separate step, and it only works if the fungus has been removed first and the structure is dry.

Prices

Inspection with moisture readings from €40. Treatment from €1.50/m², minimum from €80. If the flat is being prepared for handover or a new tenancy cycle, treatment is often combined with ozone treatment of the rooms — more about that on the page Disinfection after tenants.