improved property
(3) As used in this section the term “improved property” means a detached year-round one-family dwelling which serves as the owner’s permanent place of abode at the time of acquisition, and construction of which was begun before January 1, 1974 , together with so much of the land on which the dwelling is situated, such land being in the same ownership as the dwelling, as the Secretary shall designate to be reasonably necessary for the enjoyment of the dwelling for the sole purpose of noncommercial residential use, except that the Secretary may exclude from any improved property any waters or land fronting thereon, together with so much of the land adjoining such waters or land as he deems necessary for public access thereto.