The building envelope on a lot as defined by the minimum yard requirements for the location of a principal building, or, in the case of nonresidential uses, the location of an off-street parking lot, or a loading area, shall enclose a contiguous improvable area which is not less than the minimum improvable area required by the Schedule of Area, Yard, and Building Requirements.[1]

The contiguous improvable area shall be of such dimensions that it shall be able to contain within it the shape of a circle whose minimum diameter is not less than as prescribed by the Schedule of Area, Yard, and Building Requirements for the diameter of the improvable area.

Where single-family cluster development is permitted, the permissible number of building lots in the cluster shall not exceed the number of lots which could be developed under a conventional platting which conforms to the requirements of this section and other applicable regulations. To the maximum extent practical, the required minimum area of a cluster lot shall not be encroached upon by a wetland, wetlands transition area, stream corridor, steep slope of 15% or greater, existing or proposed public right-of-way, drainage easement, conservation easement, or Flood Hazard Area Overlay District.

Any existing detached single-family dwelling which is a conforming use but which is on a lot made nonconforming by the provisions of this section may be enlarged or expanded within its improvable area provided that such expansion conforms to all other zone district regulations.