Before the commencement of this Act or without the written approval of the tenant, the landlord may have incurred expenditure for any improvement, addition or structural alteration in the premises. Alternatively, the landlord may have made the changes after the commencement of this Act or with the written approval of the tenant. If the expenditure is not on decoration or on tenantable repairs or is usual for such premises, and if it has not been taken into account in determining the rent of the premises, the landlord may increase the annual rent by an amount not exceeding ten percent of such cost.
It is also possible that after the rent of a premises has been fixed under this Act, or has been agreed upon by the landlord and the tenant, there has been a decrease, diminution or deterioration of accommodation. In such a case, the tenant may claim a reduction in the rent.