The 3F Subdistricts are designed to preserve low-density three-family areas with a variety of housing types appropriate to the existing fabric, including one-, two-, and three-family dwellings, to preserve existing structures, to provide for new and infill construction appropriate to the existing fabric, and to allow minor changes to occur as of right. In the 3F Subdistricts, the maximum number of Dwelling Units allowed in a single Building shall be 3, and the maximum number of Town House Buildings or Row House Buildings attached in a row shall be 3.