Exterior cleaning in Liskeard
Liskeard is an old stannary town just off the A38 in south-east Cornwall, about seventeen miles from our base. Granite terraces, Victorian villas and post-war estates are mostly granite with painted render under Cornish slate.
The town sits higher and wetter than the coast, so slate roofs and gutters take a steady load of moss and debris through the year.
Lichen is a slower, harder problem than algae
Algae is a film that washes off. Lichen is an organism with a root structure that grips into the surface of slate and mortar, and it does not come off with water at any sensible pressure.
It needs a biocide and it needs time. On a badly colonised roof up at Minions or St Cleer the visible improvement continues for months, not days, and anyone promising an instant transformation is planning to use a lance on your slate.
Cornish slate roofs at altitude
Slate up here is often original, sometimes hung on the walls as well as laid on the roof, and always brittle in frost. We treat it from ladder or pole and stay off the covering.
Timing the work around the weather
There is no point applying treatment into driving rain. On the moor we plan around forecast dry windows, which occasionally means moving a booking - we would rather do that than take your money for a job the weather will wash off.
Questions from Liskeard
- Why does lichen take so long to disappear?
- Because it dies before it detaches. Weather removes the dead growth gradually over the following weeks and months.
- Would pressure washing be quicker on a slate roof?
- Quicker and much more damaging. It strips the surface of the slate and forces water under the laps.
- Do you move bookings for rain?
- For treatment work, yes. Applying biocide before heavy rain simply wastes it.