The building
A London stock brick boundary wall beneath an eave line, sheltered enough to stay damp for long periods after rain but not sheltered from seed dispersal — moss, algae, and several self-seeded weeds had established directly in the joints and along a run of eroded pointing.
The problem
This wasn't a case of atmospheric soiling needing a general clean. The joints had already lost enough mortar to give plant roots somewhere to establish, and once rooted, those roots widen the joint further and hold moisture against the brick face — a cycle that gets worse the longer it's left. Left unaddressed, root growth in mortar joints causes exactly the kind of mechanical damage that no cleaning method alone can fix.
The method
Growth was cleared by hand first — weeds and moss removed at the root where possible, not just cut back at the surface, since surface-only removal leaves the root to regrow. DOFF superheated steam then addressed the algae and general soiling across the brick face, at a setting calibrated to London stock brick rather than a harder engineering brick. Open and eroded joints were flagged for repointing in lime mortar as a follow-on phase, since cleaning the wall without addressing the joint loss that let the growth establish in the first place would only see the same problem return within a season or two.
A wall can be cleaned back to bare brick and still fail again within a year if the mortar joints that let biological growth establish aren't also addressed. We flag joint condition as part of every cleaning survey, not as an upsell after the fact.
The result
A wall clear of moss, algae, and root growth, with the joint repair identified and scoped as the next phase of work rather than treated as optional.
Looking for a similar project — the same material, the same building type, or the same problem? We are likely to have worked on something comparable and can talk it through on a free site visit.
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