According to the lease, the floors of the balconies belong to the apartment owner, whilst the walls and railings are part of the building. Balconies should only be cleaned with a dilute solution of general cleaning fluid (something like Flash or Ecover etc). Please take care to ensure that fluids do not drip onto the balconies below. Under no circumstances should pressure washers be used on the balconies or the walls.
Balcony walls, boards and railings should not be painted or varnished – it’s not allowed in the leases as it would lead to a very disparate and variable looking development.