Q: Rat infestation on rental property, who is responsible for cost?

A: If we are talking about a commercial lease, generally the lease controls. Get a lawyer to review the lease and negotiate a resolution with the neighboring property owner harboring the vermin infestation. If this is a residential lease, the answer depends a bit on the locality, but, as a general matter, there is an implied warrant of habitability, and a vermin infestation is inconsistent with that. You may have the power to withhold rent to pay for the remediation. Either way, with an $18,000 problem, it is worth it to schedule a consult with a lawyer.

A: It is unclear, but your question suggests you are the landlord. If this is a residential property, it is your responsibility to eradicate the rats. A residential tenant can start a rent escrow action in District Court to compel the landlord to deal with the issue, or terminate the lease if the infestation is a danger to health (it likely may be). If this is a commercial property, the terms of the lease need to be reviewed. The provision you cite may be deemed to apply to tenant-related activities that cause the infestation, or may be limited to taking ordinary precautions to deal with vermin, as opposed to correcting a major structural defect in the property that allows a massive infestation from a neighboring property owner. Restaurants and bars are notorious for attracting rats. As the owner of the premises, the landlord is in the best position to sue the neighboring owner to abate the nuisance. It is possible that the neighbor's business liabilty or property insurance would cover the claim. If the corrective measures to your property as the landlord involve major structural improvements and renovations, that work will be deemed a capital expenditure that improves your property--not ordinarily a tenant obligation. If the solution were simply placing bait traps and sealing openings around the exterior of the space to prevent entry, then perhaps that could be within the tenant's responsibilities under your lease provision. If the two commercial properties are part on one building structure, with common shared walls and roofs, etc., or are part of a condominium-type arrangement, there may be other avenues to pursue against the condo association or other contractual ownership arrangement of the unit owners. Usually there is property insurance for the common areas of th overall building with individual units, and there would be by-laws or other agreements in place to impose liability on the individual unit owners for addressing these types of issues. I would get more than one estimate for addressing the problem, however.