All houses become tamei from negaim except those of gentiles. Houses acquired from a gentile should be examined initially. A round house, a triangular house, a house built on a ship, or on a mast, [or] on four [horizontal] beams do not become tamei from negaim. But if it was four-sided, even if it is on four [vertical] pillars, it becomes tamei.

A house that one of its sides is covered with marble, or with bedrock, bricks, or earth, is tahor. A house that did not have stones, wood, and clay when a nega appeared on it, and then they built [lit., brought] into it stones, wood, and clay, is tahor. Similarly, a nega that appeared on a garment that was not three [fingerbreadths] by three [fingerbreadths], and then he wove it [to be] three [fingerbreadths] by three [fingerbreadths], is tahor. A house does not become tamei from negaim unless it contains stones, wood, and clay.