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.

An internal wall contains tumah. The house that is closer to the tumah becomes tamei, and the one closer to the tahor remains tahor. [If the tumah is] in the middle, both become tamei. [If there is] tumah inside one of [the houses], and there are utensils inside the wall, those [utensils] in the half closer to the tumah become tamei, and [the ones] in the half closer to the tahor remain tahor. [The utensils that are] in the middle become tamei. There is tumah in the ceiling that is between the [lower story of a] house and its upper story. [If the tumah is] inside the lower half [of the ceiling, the lower story of] the house becomes tamei, but the upper story remains tahor. [If the tumah is] in-side the upper half [of the ceiling], the upper story becomes tamei, but the lower story remains tahor. [If the tumah is] in the middle, both become tamei. [If there is] tumah in one of [the stories] and there are utensils in the ceiling, [the utensils that are in] the half nearer the tumah become tamei, and [the ones that are in] the half nearer the tahor remain tahor. [The utensils that are] in the middle become tamei. R’ Yehudah says: The entire ceiling is [ruled as] part of the upper story.

There is tumah between the joists, and underneath it is a very thin covering. If there is a handbreadth of empty space, everything becomes tamei. If there is no hand-breadth of empty space, the tumah is considered occluded. [If the tumah] is noticea-ble within the lower story, the lower story becomes tamei whether or not [there is a cubed handbreadth of empty space].

A wall that resulted from excavation is ruled as a garlic peel. How so? There is a wall between two recesses or between two underground chambers. [If] tumah is in the open areas of the catacomb, and there are utensils in the wall that are covered very thinly, [the utensils] remain tahor. [If] tumah is in the wall, covered very thinly, and in the open areas there are utensils, [the utensils] re-main tahor. [If] tumah is underneath a pillar, tumah penetrates upward and downward.