It is the intent of this chapter that nonconformities should not be expanded except as indicated herein, that they should be brought into conformity as quickly as the fair interests of the parties permit, and that the existence of any present nonconformity anywhere in the Town shall not in itself be considered grounds for issuance of a variance for any other use, lot, building, or other structure. Nothing in this chapter shall be deemed to prohibit ordinary repair and maintenance of any nonconforming building or other structure or reconstruction thereof necessitated by fire or other casualty, or replacement of existing materials, or work ordered by the Zoning Administrator to protect the public health or safety, provided such work does not increase the nonconformity.