Plaintiff made a lease of a five-floor warehouse to defendant for a term commencing April -1, 1953, and terminating March 31, 1958, with monthly payments of $1,000. The warehouse was used by defendant for storage of products manufactured by it at another location. It was damaged by a windstorm on June 11, 1957; part of the roof being blown off and part of the wall destroyed. The lease contained the following provision: “The destruction of said building or premises by fire, or the elements, or such material injury thereto as to render said premises unquestionably un-tenantable for thirty days shall at the option of said Lessor or Lessee produce and work a termination of this lease. If the Lessor and Lessee cannot agree as to whether said building or premises are unquestionably untenantable for thirty days, the fact shall be determined by arbitration ; * * * If it is determined by arbitration or agreement between the Lessor and the Lessee that said building is not unquestionably untenantable for thirty days, then said Lessor must restore said building at Lessor’s own expense with all reasonable speed and promptness and in such case a just and proportionate part of said rental shall be abated until said premsies have been restored.” On June 15th, there was a heavy rain, while the building was thus exposed to the elements, causing more damage. Thereafter, tarpaulins and roofing paper were installed to provide partial temporary covering but did not prevent water from subsequent rains coming in and leaking through the upper floors into the basement, causing the floors (except the concrete basement) to buckle. The parties agreed (July 5, 1957) that the building was 45% untenantable and that portion of the rent was abated until “the building is back in satisfactory condition for normal occupancy.”