Increase in fair rent in what case admissible

When the fair rent of a building or rented land has been fixed under section 4, no further increase in such fair rent shall be permissible except in cases where some addition, improvement or alteration has been carried out at the landlord's expense and if the building or rented land is then in the occupation of a tenant, at his request : Provided that the fair rent as increased under this section shall not exceed the fair rent payable under this Act for a similar building or rented land in the same locality with such addition, improvement or alteration and it shall not be chargeable until such addition, improvement or alteration has been completed : Provided further that any dispute between the landlord and tenant in regard to any increase claimed under this section shall be decided by the Controller :