(1)Where a landlord has at any time, before the commencement of this Act with or without the approval of the tenant or after the commencement of this Act with the written approval of the tenant or of the Controller, incurred expenditure for any improvement, addition or structural alteration in the premises, not being expenditure on decoration or tenantable repairs necessary or usual for such premises, and the cost of that improvement, addition or alteration has not been taken into account in determining the rent of the premises, the landlord may lawfully increase the standard rent per year by an amount not exceeding [ten per cent.] [Substituted by Act 57 of 1988, section 3, for "seven and one-half per cent." (w.e.f. 1-12-1988).] of such cost.
