When one wall keeps going green and the others do not
It is common for three elevations of a house to stay clean for years while one greens up again within a season. The wall is not different, its conditions are.
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- Look for a vertical stain that points to a leaking joint
- Cut back planting to open airflow where you can
- Expect shorter intervals on shaded elevations
Shade is the main driver
Algae needs moisture more than anything else, and a surface that never gets direct sun stays damp for hours longer after rain and dew. A north elevation, or any wall behind a hedge, fence or neighbouring building, holds that moisture through most of the day in winter.
Check the run-off before blaming the wall
A leaking gutter joint, a splitting downpipe seam or an overflowing hopper concentrates water on one strip of wall. That strip regrows first and fastest, and no amount of cleaning changes it until the water is redirected.
What a treatment can and cannot do
A softwash kills what is present and slows the return, but it does not change shade or exposure. On a genuinely dark elevation, expect a shorter interval between treatments than on the sunny side of the same house.
Common questions
- Will jet washing fix it faster?
- No. High pressure removes the surface growth but opens the finish, which usually makes the return quicker on render.
- Is the growth damaging the wall?
- Algae itself sits on the surface. The moisture it holds, and lichen with a stronger grip, are the parts worth dealing with.
- Can you treat just the one wall?
- Yes, single-elevation work is common and keeps the cost down.
Services involved
Similar situations
Send a photo of the elevation and the gutter line above it and we will tell you which one is causing it.
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