Damp in Portuguese homes

Introduction

Damp wall showing signs of water ingress in an older home in Cascais, Portugal.Introduction

One of the most common and frustrating problems faced by property owners in Portugal -especially in coastal areas like Cascais, Lisbon, and the Algarve - is internal mould and damp. Many expats talk about damp in Portuguese homes on local forums, and for good reason: the combination of humid winters, poor ventilation, and concrete-block construction makes these houses especially prone to moisture buildup and mould growth.

1. Why Damp in Portuguese Homes Is So Common

Most houses in Portugal are built with concrete blocks, which don’t create an effective barrier against moisture. When rainwater seeps through these walls, it often causes damp patches and humidity indoors, leading to peeling paint and mould.

To prevent this, the exterior walls should be sealed and painted with a 100% acrylic waterproof paint. A high-quality acrylic coating creates a long-lasting barrier against moisture ingress and protects the building structure.

2. Rising Damp and Renovation Mistakes

Rising damp is another widespread problem found in older Portuguese homes.

Traditionally, many houses were built with elevated entryways — steps leading up to the front door — creating natural protection against ground moisture. However, modern renovations often raise patio or ground levels, unintentionally allowing water to reach the walls. This traps moisture at the base of the structure and causes water to rise through the wall, sometimes as high as one metre.

Once that happens, the only real long-term fix is to install a new damp-proof barrier. This is done by drilling small holes every 10–12 cm and inserting Dryrod damp-proofing rods (or a similar product). These rods form a chemical barrier inside the wall that prevents further rising damp.

3. General Humidity and Indoor Moisture

Even without leaks, high humidity is a major contributor to damp in Portuguese homes. Everyday habits such as drying laundry indoors, poor ventilation, or not wiping down bathrooms after showers allow moisture to build up and lead to mould growth.

How to reduce indoor humidity:

• Open windows daily to air out the house.

• Use dehumidifiers in basements or north-facing rooms.

• Avoid drying clothes inside when possible.

• Wipe down bathroom tiles to prevent condensation.

Condensation on windows is a common early warning sign of excessive humidity. A digital hygrometer (humidity meter) can help homeowners track indoor moisture compared to outdoor levels.

4. Ageing Damp-Proof Courses

Even houses that originally had a damp-proof course (DPC) can develop moisture problems over time. These protective layers degrade, allowing water to penetrate.

When re-plastering or repairing walls, homeowners should use breathable, waterproof plaster rather than traditional cement render, which traps moisture inside the walls and worsens the problem.

5. Signs of Damp to Watch For

If you suspect damp in Portuguese homes, look for these warning signs:

• Peeling or blistered paint

• Musty odours

• Mould patches or dark stains on lower walls

• Flaking plaster near skirting boards

• Cold, clammy walls

These signs often indicate water ingress, rising damp, or internal condensation problems that need professional attention.

Conclusion

Damp and mould are common in Portuguese homes, but they’re not impossible to manage. With proper maintenance, ventilation, and waterproofing, you can protect your property from long-term moisture damage.

If you’re unsure where the damp is coming from, it’s worth arranging a professional home inspection in Cascais or Lisbon.At AllProperty, we use thermal imaging and moisture diagnostics to find the real source of damp and offer effective, lasting solutions.

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Frequently Asked Questions

QUESTION: Why are Portuguese homes more prone to damp?

ANSWER: Portugal’s humid winters, concrete-block construction, and limited ventilation make homes especially vulnerable to moisture, mould, and condensation.

QUESTION: How do I tell the difference between rising damp and a leak?

ANSWER: Rising damp starts at the base of walls and moves upward. A leak causes isolated wet patches higher on walls or ceilings. Thermal imaging confirms which one it is.

QUESTION: Can damp affect my health?

ANSWER: Yes. Damp and mould can trigger allergies, asthma, headaches, respiratory irritation, and sleep problems — especially in bedrooms.

QUESTION: What causes damp problems in older Portuguese properties?

ANSWER: Many older homes lack modern waterproofing, have worn damp-proof courses, or have exterior walls that were never sealed with acrylic waterproof paint.

QUESTION: Will repainting over damp solve the problem?

ANSWER: No. Painting over damp traps moisture and makes it worse. You must fix the source of moisture before repainting.

QUESTION: Can a dehumidifier get rid of damp completely?

ANSWER: No. A dehumidifier helps control indoor humidity but cannot fix leaks, rising damp, or structural moisture ingress.

QUESTION: When should I call a professional for damp?

ANSWER: If you see blistering paint, mould patches, musty smells, or cold, clammy walls, it’s time for a professional inspection with thermal imaging and a moisture meter.

QUESTION: Can thermal imaging detect damp behind walls?

ANSWER: Yes. Thermal imaging identifies hidden moisture, cold bridges, leaks, and insulation failures long before mould becomes visible.