The Court of Appeal has recently had to decide what is meant by "structure". The matter arose in the case of Grand v Gill. It involved a letting of a dwelling for less than seven years. With such letting a landlord's repairing covenant is implied into the tenancy by section 11 Landlord and Tenant Act 1985. This requires the landlord to repair the structure of the dwelling among other matters. In Grand v Gill, internal plaster was in disrepair. The point at issue was whether the plaster was part of the structure. The court decided it was, so it was therefore the landlord's duty to repair the plaster as part of its repairing covenant under section 11.
Read about the case here