Why does a patio turn green?

Short answer

Algae thrives where shade, moisture and organic debris persist. Poor drainage and porous paving can keep the surface wet for longer.

Answers about paving materials, algae, pressure, drainage, re-sanding, sealing and surface aftercare. The exact recommendation can change with the building, surface condition, access and the scope agreed for the visit.

What this means for your property

Start with the visible issue and the location where it occurs. Photographs, floor level, surrounding surfaces and access details help distinguish routine maintenance from restoration, repair or specialist access.

A professional quotation should define what is included, state any limitation and avoid promising that cleaning will correct damaged glass, failed seals, leaks or structural defects.

How to apply this answer

Paving material, joint condition, drainage, coatings and contamination determine the safe treatment. Pressure alone is not a universal solution: a test area and controlled technique help protect softer stone, unstable joints and neighbouring surfaces.

Connect the answer with observable facts at the property. Note where the issue occurs, which elevations are affected and whether it changes after rain, heating, building work or seasonal growth.

For “Why does a patio turn green?”, use the confirmed answer as the starting point, then describe the actual building, affected surface and access. This helps distinguish ordinary maintenance from a condition that needs closer assessment.

What to confirm before booking

Record the property type, number of storeys and the position of the affected surface. Mention locked access, balconies, basement areas, roof glazing, fragile finishes or public routes that could influence the method.

Ask for a quotation that names the included work and any limitation. This keeps the answer specific to “Why does a patio turn green?” and prevents an unrelated repair, restoration or additional service from being assumed.