Red staining on outside wall

[Jan Harbour]

We live in Carmarthenshire - our property and several others have red/brown staining on outside walls - especially the end facing the prevailing winds. Some use bleach to remove - a short term solution and not a choice for us as we do not want to damage plants close by. Can anyone advise a solution?

 

[JohnD]

photos please

are these stone walls?

are they frequently damp?

does it appear on roofs? or on patches of wall sheltered e.g. by eaves?

is farmland soil in your area red after ploughing?

 

[Jan Harbour]

No - not always damp - hope photos help

 

[JohnD]

is it stone?

I can only think of lichen (chemicals will kill it) or rust stains if the house is built of iron-containing stone or sand. Some districts with a high iron content you can see it in old drystone walls, quarries and soil colour, and brown staining round old taps.

Lichen is also seen on old apple trees, shaded roofs, tombstones.

Lichen grows on the surface so can (with difficulty) be scraped off, and tends to hold mixed colours.