Extension or enlargement. ["Extension or enlargement" shall mean: in the case of a nonconforming use in a building, the enlargement of such building so as to create additional floor area, or the extension within any existing building to any portion of the floor area therein not formerly used for such nonconforming use, except where such additional floor area was manifestly designed for such use at the time such use became nonconforming or the extension of the use to an area outside the building; and in the case of a nonconforming nonbuilding use, the use of any additional land on which no substantial operations were previously conducted, provided that any such extension or enlargement is on the same lot occupied by the nonconforming use on the effective date of this code.] A nonconforming use shall not be extended except as follows: To the extent the district bulk regulations permit, and on application of the Board of Appeals, any use, except a sign, first permitted by right or by special permit, in any district, may be extended up to but not exceeding an aggregate increase of 50% in its floor area or of its land area occupancy if a nonbuilding use. However, this provision may be used only once for each such use.