Existing buildings which are placed closer to front, side or rear lot lines than permitted by this chapter shall not be expanded so as to encroach farther into the required setback without the issuance of a variance. Expansions within front, side or building setbacks are permitted without issuance of a variance if they are in line with the existing building, as illustrated below. It shall be presumed that any expansion into the front setback on Broadway will be detrimental to the health, safety and welfare of the community.