Façade cleaning
What are the green or black marks on an Algarve façade?
Colour alone cannot diagnose a stain. Shade, slow drying, runoff, irrigation, dirt and biological growth can overlap, so the useful question is why that area stays wet or dirty longer than the wall around it.
Updated 17 September 2026 · 5 min read
Read the pattern, not only the colour
Marks concentrated below parapets, gutters, air-conditioning drains or sprinklers suggest a water path. Growth on shaded elevations or behind dense planting often points to slower drying. Uniform dirt near a road or exposed edge may have a different cause.
A photograph after rain and another after two dry days can reveal more than a close-up taken once.
- Show the whole elevation
- Include the roof edge, drain or plant above the mark
- Photograph one close detail with a scale reference
Clean without hiding the cause
The surface material and existing coating decide the method. Painted render, ETICS, stone and brick do not tolerate the same pressure or chemistry. Start with a discreet test, controlled application and proper protection of plants, glazing, metal, electrical points and pool water.
If moisture is still active, painting over the mark can trap the decision rather than solve it. Clean, allow the surface to dry and investigate recurring water before choosing a coating.
When the problem needs a broader review
Escalate when the mark returns quickly, the coating blisters or peels, the wall remains damp in dry weather, salts appear or the same area is wet indoors. Those signs can require drainage, sealing or substrate work outside a normal cleaning scope.
- Record how quickly the mark returns
- Note irrigation and air-conditioning discharge
- Mention indoor odour, damp or damaged finishes
Before requesting an estimate
Before requesting an estimate
- One wide photograph of the affected elevation
- Close-ups of the mark and coating condition
- Roof edge, drains, irrigation and nearby planting
- A note on shade, recent rain and how quickly it returns
Sources and further reading
Product instructions and the condition of the property always take priority over general guidance.
