My landlord has been reconstructing the basement and he is 4 months overdue.?

So the increase for the basement has already been written into your lease and executed? If not, you don't have a basement for the contracter to have his things in, that basement is not yet yours in the terms of the lease. If a construction timeline is not listed in a written agreement, the landlord can take ten years to complete construction if he/she chooses and that's just the way it is.