Triple net lease - landlord wants me to pay $85K for roof replacement on 40-year-old building

I signed a 5-year NNN lease for a retail space in Columbus, Ohio. I'm 18 months into the lease. The building was built in 1985 and the roof is original.

Landlord just sent me a bill for $85,000 for a full roof replacement. Says under the NNN lease, I'm responsible for "all repairs and maintenance including structural."

This seems insane. The roof was 40 years old when I moved in - of course it needs replacing. How am I responsible for a capital improvement on a building I don't own?

Is this normal for NNN leases? Do I really have to pay this?

This is super helpful. I'm going to propose the amortization approach.

One more question: if the landlord refuses and demands full payment, what happens? Can they evict me? Can I withhold rent?