A wall constructed to be part of a house is ruled half and half. How so? An exterior wall contains tumah: [if the tumah is] in the inner half [of the wall], the house be-comes tamei, and someone standing above [the wall] remains tahor. [If the tumah is] in the outer half, the house remains tahor, and someone standing above [the wall] becomes tamei. [If the tumah is] in the middle, the house becomes tamei. [Regarding the per-son] standing above [the wall] — R’ Meir declares him tamei, but the Sages declare him tahor. R’ Yehudah says: The entire wall is [ruled as] part of the house.