Hi,
I see the demand of the owner to be quite reasonable, but also it is imperative to refer the lease agreement before taking a defense. I advise that both tenant and landlord stick to the conditions mentioned in the lease agreement.
Normally, any alteration or modification should not be carried out with the permission of the landlord, unless it is very essential, arising out of emergency, any damage making the premises unusuable without immediate action.
so, the landlord has every right to demand that the modification cost be borne by the tenant, given that the modification is completely nonbeneficial to him.
Cheers!