what is physical housing?
Apparently this term is used to list the characteristics of any housing units. It may include accessibilty for physically challenged people -- or any other criteria needed for a particular population. Check this site.
http://factfinder.census.gov/servlet/STTable?_bm=y&-qr_name=ACS_2006_EST_G00_S2504&-geo_id=01000US&-ds_name=ACS_2006_EST_G00_&-_lang=en