Readers' forum : Conversion time

In 1997 my client purchased a disused Victorian water tower on the roof of which some telecom operators had installed antennae for which they paid a charge. Six years later the antennae were moved to a temporary mast within the curtilage of the property and work started to convert the building into a single residential dwelling. When the conversion was completed a year later the building became the owner’s only or main residence. When the telecom operators replaced their antennae after the work was completed they did not have exclusive use so there is no main residence restriction.

Is time-apportionment the only method over the whole period of ownership by which the gain on the disposal is apportioned under TCGA 1992 Sch 4ZZC para 4 to determine the residential gain and non-residential gain? Valuations show that the property gained little in value during its commercial...