In short
- Mould grows wherever damp lingers: cold corners, around windows, in the bathroom.
- The usual causes are poor ventilation, cold walls and leaks from the roof or pipes.
- At a viewing, look for dark patches, bubbling paint, fresh paint in one corner and a musty smell.
- If the cause is in the building, such as the roof or facade, cleaning alone won't fix it.
Why damp and mould appear in a flat
Mould needs moisture, coolness and still air. In a flat, that usually happens in one of three ways.
- Condensation. Warm, moist air from cooking, showers and breathing cools on a cold surface and turns into water. Typical spots are outside-wall corners, window reveals and the wall behind a wardrobe on an outside wall.
- Leaks. Water comes in from outside or from pipes: a damaged roof, cracks in the facade, joints between wall panels, risers or the neighbour upstairs.
- Poor ventilation. New plastic windows with no airing and blocked ventilation grilles keep moisture inside.
Specialists from Rīga Stradiņš University point out that mould can also signal a building in poor technical condition with low energy efficiency. That makes it a buyer's issue too.
How to spot mould at a flat viewing
Before a viewing, sellers often air the flat, repaint or cover problem areas with furniture. Look closely at the places where trouble shows first.
- Outside-wall corners near the ceiling and floor, especially on the north side
- Window reveals, sills and seals: black spots or water drops
- Behind large furniture against an outside wall: ask if you may move it
- In the bathroom: tile grout, ceiling, behind the washing machine
- Fresh paint in just one corner or on the ceiling
- Bubbling paint, peeling wallpaper, cracks in the plaster
- Smell: stale, cellar-like air even in an aired room
- Ventilation grilles: hold a strip of paper to see if they draw
- On the top floor: stains on the ceiling from the roof
The building or the occupants' habits
For a buyer, the key question is where the cause lies. The location gives you a rough answer.
| What you see | Most likely cause | Who fixes it |
|---|---|---|
| Patches near windows and in the bathroom | Poor airing, condensation | The occupant |
| Patches in outside-wall corners | Cold wall, blocked ventilation | The occupant and the building |
| Ceiling stains on the top floor | Damaged roof | The building |
| Damp strip along a panel joint | Failed facade joints | The building |
| Stain by a riser or on the ceiling | Leak from pipes or a neighbour | The building or the neighbour |
What to do if there is already mould
Specialists advise washing off visible mould, drying the surface and the room thoroughly, and repeating. Wear a respirator while cleaning, even as a healthy adult. Chemicals are rarely needed, and they can harm health too.
Then deal with the cause. Air rooms briefly and often, don't dry laundry indoors without airing, leave a gap between furniture and outside walls, and check the ventilation. If the patches come back, the cause is in the building and you need to talk to the building manager.
If small children, older people or anyone with allergies or asthma will live in the flat, mould is a more serious matter. The WHO considers indoor damp and mould a risk factor for respiratory illness.
Mould and the price
If ventilation and a repair inside the flat can solve the mould, it's a point for negotiation. Estimate the cost of the work and use it when you make an offer. If the cause is the roof or facade, the fix depends on the whole building, so check the repair fund.
Common questions
Is mould in a flat dangerous to health?
For a healthy person it's usually not serious, but children, older people and people with allergies or asthma face a higher risk.
How do I tell condensation from a leak?
Condensation usually sits by windows and in outside-wall corners and grows in winter. A leak leaves stains near the ceiling, risers or joints and spreads after rain.
Is anti-mould paint enough?
Not while the cause remains. Deal with the source of damp first, then redecorate.
Who pays if the mould comes from the roof?
The roof is shared property of the building, so all owners decide on and pay for its repair together.
Sources
- Vai un kā cīnīties ar pelējuma sēni mājoklī. Skaidro speciālisti · LSM, 2023
- WHO guidelines for indoor air quality: dampness and mould · World Health Organization, 2009
- PTAC ieteikumi, iegādājoties dzīvokli · LV portāls, 2025
This article is for information only and is not legal, financial or tax advice. It may contain mistakes or be out of date, so check it against official sources or with a specialist before you decide. m²cena accepts no liability for any loss or damage arising from the use of the information in this article.