Cleaning cob and granite on the EX20 moor edge
EX20 is the north-western corner of what we cover, and it is also the corner with the oldest fabric. Cob under lime, granite rubble and thin coats of painted render sit in a high-rainfall belt where growth returns faster than it does closer to the coast.
EX20 covers 8 places we work in, 18.2 to 19.9 miles from our base at 58 Reddington Road, Plymouth (Devon, West Devon Borough Council) - all inside our 20-mile radius of Plymouth.
Why growth is heavier up here
Rainfall on this side of the moor is measurably higher than in the city, and the drying window is shorter. Walls stay damp into the middle of the day, which is exactly the condition algae and lichen need. The result is not dirt in the usual sense - it is living growth rooted into a soft surface.
That changes the aim of the job. Blasting it off leaves the roots and damages the surface. A biocide treatment kills the colony and the weather removes it over the following weeks, which on cob is the only sane approach.
Cob and lime need low pressure and patience
Cob walls are earth. Behind a lime or breathable coat they are stable for centuries, but they will not tolerate a pressure lance, and a sealed modern paint traps the moisture that is meant to move out through the face.
So on cob we work at garden-hose pressure with a soft wash applied and left to dwell, and we keep the run-off away from the base of the wall where cob is most vulnerable.
Scheduling this far out
EX20 sits between 18 and 20 miles from our PL3 base, so these are planned days rather than call-outs. We group work in the district and try to keep neighbouring properties on the same visit, which keeps travel sensible for everyone.
Reached via local lanes off A386. Recorded wall finishes: cob, granite, painted render. Roof coverings: slate, natural slate.
Towns and suburbs in EX20
Villages and neighbourhoods in EX20
Questions we get asked in EX20
- Will a softwash harm a lime-rendered cob wall?
- Not when it is applied at low pressure and rinsed gently. The damage on cob comes from pressure and from sealing the face, not from the treatment itself.
- How long before the walls actually look clean?
- On a heavy lichen job the colour keeps improving for several weeks as rain carries the dead growth off. It is slower than pressure washing and it lasts much longer.
- Do you come out this far for a single job?
- Yes, but we will usually offer you a date when we are already working in the district rather than the same week.