Part 1 of the Landlord and Tenant Act 1987, as amended by the Housing Act 1996, introduced the concept of the residential tenants' rights of first refusal.
Right of first refusal is where a landlord is proposing to sell his interest in a building containing flats, the right may exist, and by law, the landlord must first offer it to the qualifying tenants before offering it on the open market.
For the right of first refusal to exist, the premises, the landlord and the tenants must meet certain requirements.
The Premises are defined as the "whole or part of a building" containing at least two flats, but no more than 50% of the premises are to be in non-residential use.
The property litigation legislation is silent on what is intended as a building, but it is generally understood to mean a separate building, or in some cases, a part of a building which may be divided vertically from another part.
In the absence of a legal definition, you should apply the ordinary meaning of the word as being 'an inclosure of brick or stone covered by a roof'.