Mould is a symptom. This page helps you work out which of five possible causes applies in your case.
Mould spores are in the air permanently — indoors, outdoors, in new builds and old houses alike. They cannot be removed from the environment, and that is not the goal. Spores are harmless as long as they do not start growing.
Growth needs three things: a food source (almost any organic material — wallpaper, timber, dust, the paper facing of plasterboard), a suitable temperature (ordinary room temperature is ideal) and moisture.
The first two cannot be changed. So all practical work with mould is work with moisture.
The fungus does not grow where it is dirty. It grows where a surface stays damp long enough.
Physically, the decisive concept is the dew point. At a given temperature, air can hold only a certain amount of water vapour. When it meets a surface cooler than that threshold, the excess moisture settles on it. So condensation is a relationship between two quantities: how humid the air is and how cold the surface is. Change either one and the problem disappears — which is exactly why the answer is sometimes airing and sometimes insulation.
| Cause | How it shows | What the fix requires |
|---|---|---|
| Condensation on a cold surface | Patches on external walls, in corners, behind furniture | Changing heat and airflow, insulation |
| Insufficient air exchange | Misted windows, humidity in several rooms | Restoring ventilation, providing an air supply |
| Leak | A local patch with a clean edge | Repair — treatment without it does not work |
| Rising damp | Lower part of walls, basements, ground floors | Damp-proofing |
| Cold bridges | Corners, slab junctions, balcony slabs | Correcting the insulation |
The most common in practice is the first — condensation on a cold surface. In Riga's housing stock it is usually a combination: airtight new windows plus ventilation designed for different conditions.
The type of building does not determine the cause, but it changes its likelihood dramatically. The three main types in Riga's housing stock behave differently.
That is why the first questions at an inspection are about the building rather than the patch: what kind of building it is, when the windows were replaced, whether the facade is insulated, whether the ventilation is natural or mechanical. Those four questions rule out a large share of the possibilities.
Condensation-driven mould behaves predictably in Latvia. During the heating season the surfaces of external walls cool down, while the amount of moisture in the indoor air stays the same or rises: windows are kept shut, airing happens less often, laundry is dried indoors. So patches appear between October and March, and in spring they often look as though they have "stopped".
Spring and autumn are a risk zone of their own. The heating is not on yet or no longer on, the structures are cool, but the outdoor air is damp. In these months problems appear in uninsulated utility rooms, on glazed balconies, in basements and in unheated rooms.
A practical diagnostic follows from this. If a patch appears every winter and looks unchanged in summer, it is almost certainly condensation. If it appeared after a specific event — rain, flooding, a refurbishment — and keeps growing regardless of the season, it is a leak or residual construction moisture.
This list helps you understand the direction, but it does not replace a measurement. Two visually identical patches can have entirely different causes.
Before you get in touch, there are a few checks you can do yourself, and they often answer half the questions:
We look at the affected areas, their position and character — that already says a lot about the cause.
We determine relative humidity in the rooms and compare it with the norm.
We measure moisture in the wall or structure — this separates a leak from condensation.
We find the coldest zones, where condensation settles first.
We state the cause, the treatment needed and what has to change so it does not repeat.
A measurement separates two things the eye cannot: how damp the air is and how damp the material is. If the air is humid but the material is dry throughout the wall except for a thin surface layer, it is condensation. If the moisture in the material at one point is many times higher than a metre away, the water is coming from the structure — and then we look for the source.
We also tell you when treatment is not needed. If the patch turns out to be an old dry water stain or salt efflorescence, there is nothing to treat — what is needed is redecoration and, if the readings show it, dealing with the moisture source.
Inspection with moisture readings from €40. If we go on to carry out treatment after the inspection, we credit the inspection fee against the total price of the work.
No. Mould is an indicator of moisture, not of cleanliness. A very clean flat with poor ventilation will get it; a moderately clean one with good air exchange will not.
Roughly 40–60% in living rooms. A hygrometer costs a few euros and is the single most useful tool for prevention.
Yes, and that is typical of condensation. In winter the differences in surface temperature are greater, so condensation forms more easily.
Describe the situation — we will tell you whether treatment is needed at all, and which one.
Fill in the form — we will call you on the number you provide, ask a few clarifying questions and propose a solution.
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