Mould in Residential Properties: Case Study in Cascais
Mould in residential properties is often the first visible sign that something else is happening within a building.
Finding the reason for the moisture is therefore an important part of understanding why mould has appeared and whether it is likely to return.
A residential property in Estoril provided a useful example. Visible mould was present in a children's bedroom, while moisture readings in several rooms revealed a separate pattern affecting the lower sections of exterior walls.
The investigation showed that the property required closer attention in more than one area, rather than the visible mould being treated as an isolated problem.
What Did the Inspection Find?
Two distinct patterns emerged during the assessment.
In one bedroom, mould was visible near ceiling level beneath a balcony. Elsewhere, elevated readings were recorded at the base of walls in the lounge, office and main bedroom.
The location and distribution of these findings suggested different causes, requiring the affected areas to be considered separately.
What Was Causing the Moisture Above the Bedroom?
The mould in the children's bedroom was located close to ceiling level, directly below a balcony. This made the condition of the balcony waterproofing and drainage particularly relevant.
Further investigation identified moisture behind the affected area, with the evidence indicating water ingress associated with failed balcony waterproofing above the room.
This type of problem can be difficult to identify from the bedroom alone. The visible mould may appear to be a localised wall or ceiling issue, while the source of the water is actually located in an external building element above.
What Did the Moisture Readings Show?
Measurements taken in the lounge, office and bedrooms showed elevated readings at the base of several walls.
The distribution of these readings was consistent with a rising damp pattern, indicating that another moisture-related condition was affecting the property.
This was significant because repairing the balcony would not address moisture occurring at lower wall level elsewhere in the building.
Why Were There Two Different Moisture Problems?
The findings illustrate why the location of visible mould does not necessarily tell you everything about the moisture affecting a property.
The affected bedroom had evidence consistent with water ingress from defective balcony waterproofing, while the lower wall readings indicated a separate pattern consistent with rising damp.
These problems would require different remedial approaches. Repairing the balcony waterproofing would address the source of the water entering from above, but it would not resolve moisture affecting the lower sections of other walls.
Understanding the distinction between different moisture sources is therefore important when deciding what needs to be investigated and repaired.
Why Isn't Treating the Mould Enough?
Mould can be cleaned and affected surfaces can be repainted or replastered, but these treatments deal with the visible result rather than necessarily addressing the conditions that allowed the mould to develop.
If moisture continues to enter or accumulate within the building, the affected area may deteriorate again.
In the Estoril property, treating the mould in the affected bedroom without addressing the defective balcony waterproofing would have left the source of the water unresolved. The separate moisture affecting the lower walls would also have remained.
The appropriate repair therefore depends on understanding what is causing the moisture in the first place.
What Can Thermal Imaging Show?
Thermal imaging can highlight unusual temperature patterns that may indicate an area requiring closer investigation.
In the children's bedroom, the thermal image showed a cold anomaly around the affected area, helping draw attention to a possible moisture-related condition behind the wall.
The thermal finding was considered alongside moisture measurements, the position of the balcony above, visible evidence and the wider condition of the property.
Thermal imaging does not directly detect moisture. Its role is to identify temperature differences that may provide useful information during a wider investigation.
What Does Mould in Residential Properties Tell You?
This case demonstrates the importance of looking beyond the most obvious sign.
Visible mould was only one part of the picture. Further investigation revealed that the property had moisture affecting different areas for different reasons, including water ingress associated with balcony waterproofing and a separate pattern consistent with rising damp.
For homeowners, this means that recurring or unexplained mould deserves closer attention, particularly when the source is not obvious from the affected surface.
For buyers, visible mould can also be a reason to investigate the surrounding building elements and understand whether there are wider moisture-related concerns before purchasing the property.
What Should You Do If Mould Keeps Returning?
If mould repeatedly appears after cleaning or redecorating, the next step should be to investigate why the area remains susceptible to moisture.
Look at the surrounding building elements rather than focusing only on the affected surface. Depending on the location, this may include balconies, roofs, external walls, plumbing, drainage, windows or areas where condensation could occur.
Where the source is not immediately apparent, targeted moisture measurements and other diagnostic methods can help establish which areas require further investigation.
Finding the cause early can also help prevent unnecessary work being carried out on finishes that may become affected again.
Frequently Asked Questions
Can mould have more than one cause in the same property?
Yes. Different parts of a property can be affected by different moisture sources, as this Estoril case study demonstrates.
Does visible mould always mean there is a leak?
No. Mould can be associated with several moisture conditions, including water ingress, condensation and other building-related moisture problems. The cause needs to be established from the available evidence.
Can thermal imaging help find hidden moisture?
Yes. It can highlight areas that may require closer investigation, particularly when combined with moisture measurements and other inspection evidence.
What should I do if mould keeps coming back?
Investigate the source of the moisture rather than repeatedly treating the visible mould. The appropriate next step will depend on the location and evidence found.
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