When is a house no longer a house?

Yeso, New Mexico

For all practical purposes, a house is no longer a house when it becomes uninhabitable. But for the purposes of history, the answer may be never. When the visible ruins disappear the archeologists step in with shovels, ground penetrating radar, and the such. In that spirit, I'll call this Old House 124. Perhaps, in the future, it will lead someone to where it once stood.