(a) The number of new principal buildings associated with a project shall be the net increase in principal buildings on a project site. A project that does not result in such a net increase (such as tearing down an existing principal building and constructing a new principal building elsewhere on the project site) will not be considered to involve a new principal building for the purpose of applying the overall intensity guidelines.

(b) Where a purely mathematical application of the overall intensity guidelines to a given project site results in a fractional number of permissible principal buildings, that number shall be rounded to the nearest whole number, which shall be the arithmetically permissible number of principal buildings.

(c) As many as a 10 percent greater number of principal buildings than are arithmetically permissible may be permitted where justified by natural resource and public considerations, such as where a common sewerage system is provided or where the project would be substantially invisible from travel corridors.

(d) The overall intensity guidelines shall apply to all principal buildings which are part of a project, except single family dwellings or mobile homes which are proposed to be located on (1) a preexisting vacant lot of record as described in section 811(1)(a) of the Adirondack Park Agency Act, (2) a lot located in a preexisting subdivision which has received New York State Department of Health approval, or (3) a lot created by bona fide gift, devise or inheritance where the donor or decedent continuously owned the property since prior to May 22, 1973 and the recipient was a member of his immediate family.