Are the basement stairway walls considered part of the main floor? My understanding is that the entry going into the basement is considered part of the basement and not the main level.
Anything beyond your basement entrance door is considered basement which is not included in your house square footage. If the door is at the bottom of the stairs after a landing area then that landing is included in house Sq ft even though that landing is in the basement.
Search the TrustedPros directory and discover the best contractors in your area.Find your home service pro