Houses with tzara'at blemishes are deemed impure when the blemishes are the length of two grisim. Thus the width of the blemish is approximately the size of a place where six hairs grow on the body and its length is a place for 12 hairs. It must be rectangular. Any blemish on a house smaller than this measure is pure. All of the measures are halachot transmitted to Moses at Sinai.
There are three distinguishing marks of impurity for tzara'at in houses: an intense green or intense red appearance and the spreading of the affliction. These are all explicitly mentioned in the Torah. The two abnormal appearances can be combined with each other. If a blemish spreads to the place immediately adjacent to it, even the slightest spread is considered a sign of impurity. If it spreads to a distant place, the new blemish must be a gris. When a blemish returns after the house is plastered, it must be two grisim.
Blemishes on buildings do not impart impurity until the abnormal appearance is seen below the surface of the wall, as implied by the term shika'rurot, interpreted as meaning "sunk in the walls," used by Leviticus 14:37. A blemish with either of these two appearances causes the building to be isolated or definitively deemed impure. If it increases in size, it should be torn down and if it spread after it was replastered, the entire house must be torn down, as will be explained.
🏠 House Blemish Basics
House tzara'at requires a minimum of two grisim (6 hairs wide × 12 hairs long, rectangular). Three signs apply: intense green, intense red, and spreading — all explicitly stated in Torah. The blemish must appear sunken below the wall surface. The two color signs can combine; spreading immediately adjacent counts for any size; spreading to a distant place must be a gris; a blemish returning after plastering must be two grisim.
When a blemish appears in a house, even a sage who knows that it is definitely a blemish should not definitively say: "A blemish appeared in my house." Instead, he should tell the priest, "It appears that a blemish appeared in my house. The priest will then issue an order to remove everything from the house, even bundles of wood and bundles of reeds. Afterwards, the priest will come and inspect the blemish.
We do not open windows in a closed house to inspect its blemishes. Instead, if a blemish is not visible in its present state, it is pure. After a priest will inspect a blemish, he should depart and stand at the entrance to the house, near the lintel and either isolate, deem definitively impure, or release the house from the inspection process, as ibid.:38 states: "And the priest shall leave the house, going to its entrance... and he shall isolate the house." He should not isolate a house while he is in his own house, in the blemished house, or under its lintel. Instead, he should stand at the side of its entrance. If he stood under the lintel or went to his own house and isolated a house, it is isolated.
🔍 How to Report
When a blemish appears on a house, even a scholar must speak tentatively — saying 'it appears to me as a blemish' rather than declaring it definitively. This allows the priest to order the house emptied first (even bundles of wood), protecting the contents. A dark room is not opened for more light — if the blemish isn't visible naturally, the house is pure. The priest examines inside but pronounces the ruling while standing at the entrance, not inside the house.
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Structural Requirements for a House to Contract Tzara'at
A house is not deemed impure because of a blemish unless it is four cubits by four cubits or more, it has four walls, and it is built on the earth with stones, earth, and wood, for Leviticus 14:45 mentions: "its stones, its wood, and its earth." If, however, it is less than four cubits by four cubits, it is round, triangular, or pentagonal, it was built on a ship or suspended on four beams, it is not susceptible to the impurity stemming from a blemish. If it was built on four pillars, it is susceptible to the impurity stemming from a blemish.
How many stones must be in a house? No less than eight, two stones on each wall so that every wall would be fit to have a blemish. For a house it is not susceptible to the impurity stemming from a blemish unless a blemish the size of two grisim appears on two stones, as indicated by Leviticus 14:40 which mentions: "the stones in which the blemish is located." How many boards must it contain? Enough to place under the lintel. How much earth? Enough to place between one broken stone and another. If a house contained less than these measures, it is not susceptible to the impurity stemming from a blemish.
Neither bricks nor marble are considered as stones in this context. When there is a house that one of its walls is coated with marble, another is made from a boulder, the third, of stones, and the fourth, from earth, it is not susceptible to the impurity stemming from a blemish.
When a house did not have the required measure of stone, wood, and earth and a tzara'at blemish was discovered in it and then additional stones, wood, and earth was brought for it, it is pure.
When plants were used as the covering for a house, they are considered as a permanent part of it. Since they are serving the purpose of wood, they are considered as wood. If the house becomes impure, they contract the severe impurity associated with it, as will be explained.
🏗️ Structure Requirements
A house must be at least 4 × 4 cubits, have exactly four walls, be built from stones, earth, and wood, be on the ground (not on a ship or suspended). Minimum: 8 stones (2 per wall), enough wood for a lintel, enough earth for mortar between stones. Bricks and marble do not count as 'stones.' A house lacking proper materials when the blemish appears but then adds them is pure.
Houses located in Jerusalem and the Diaspora are not susceptible to the impurity stemming from blemishes, as implied by Leviticus 14:34: "in a house in the land of your ancestral heritage." Jerusalem is thus excluded, because it was not divided among the tribes. The houses of gentiles in Eretz Yisrael are not susceptible to the impurity stemming from blemishes.
When a gentile lives on one side of a house and a Jew on the other side or one side of a house was in Eretz Yisrael and the other in the Diaspora, it is not susceptible to the impurity stemming from blemishes. All other buildings in Eretz Yisrael are susceptible to the impurity stemming from blemishes. This applies regardless of whether they were colored naturally or colored because of human activity.
The house of a woman, a house belonging to partners, a synagogue or a house of study that has a dwelling for attendants or students is susceptible to the impurity stemming from blemishes.
The walls of a feeding stall and the walls of a partition in a house are not susceptible to the impurity stemming from blemishes.
הלכה ט״ז׳
🗺️ Eligible Houses
Only houses in the Land of Israel — not Jerusalem (which was not divided among tribes) and not the Diaspora — contract tzara'at. Gentile houses in Israel are exempt; purchasing from a gentile requires initial assessment. A house jointly owned by a Jew and gentile (one wall each) is exempt. Synagogues and study halls with residential quarters for attendants/students are susceptible. Partition walls and feeding stalls inside a house are not susceptible.
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🎓 Key Principles
Chapter 14
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Houses Have a Higher Minimum House tzara'at requires two grisim — double the minimum for human or garment tzara'at — reflecting the larger scale of the affliction and a higher threshold for declaring a building impure.
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Tentative Language Protects Property Even a scholar who certainly recognizes a house blemish must report it tentatively, allowing the priest to order the house emptied before the formal declaration — protecting the contents from becoming impure.
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Natural Materials Define a House Torah law requires stones, earth, and wood as the three natural building materials — a house of bricks, marble, or incomplete materials cannot contract tzara'at regardless of its appearance.
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Territorial Limitation House tzara'at is limited to the portion of Israel divided among the tribes — Jerusalem and the Diaspora are excluded, expressing the unique connection between the Land's holiness and the tzara'at warning system.