Repairs to non-conforming use: On any building devoted in whole, or in part, to any non-conforming use, work may be done in any period of 18 consecutive months on ordinary repairs, improvements, modernization, or on repair or replacement of nonload-bearing walls, fixtures, wiring, or plumbing to correct deterioration, obsolescence, depreciation, and wear. Such repairs, improvements, replacement, or modernization activities shall be permitted providing the total area (in sq. ft.) of the building as it existed at the effective date of this chapter shall not be increased. Repairs begun within the required 18 consecutive months but not completed upon the expiration of the permitted time period may be completed provided the permits for the repairs have been issued, approved, and maintained, and the work has continued without interruption to eventual completion.