A structure such as a demountable building (10) including a base (11), a plurality of modular units (12–17) which are arranged for connection to the base (11). Each unit is fitted out with functional elements to enable that unit to perform a predetermined function in the operation of the building (10). Each unit (12–17) and its associated functional elements being operative to be connected to, or removed from, the base (11) as a single unit.