While painting in north London we inspected the roof and walls for holes and defects. Repair of these keeps out rain and raccoons.
We cleaned the mossed and lichened slates too. Moss will drop into gutters and block them. Lichens eat slates.
Dormer windows at high level suffer most from weather and lack of care.
We replaced some rotted timber on these and stripped much of the wood, particularly the hardwood cills so they’d get a proper coat of aluminium primer.
As a commercial painter and decorator in South-West London we are always happy to inspect and correct other problems that are only apparent when we have established access to the roof and upper floors.