1) under section 14 of Maharashtra rent control act it is duty of landlord to keep the premises in good and tenantable repair
2) if landlord neglects to carry out repairs tenant can issue 15 days notice to landlord and on his failure tenant can carry out the repairs and deduct the expenses from rent payable . the amount deducted should not exceed one fourth of rent payable .
3) you have not carried out any structural changes in flat .
4) you do not need landlord permission to carry out tenant able repairs
5) Tenantable repairs as defined by section 342 of the MMCA, includes providing guniting to wall structures, plastering, painting, flooring, repairing of the bath, WC and wash places and replacing electrical fittings and several items