The Torah instructs in the Book of Debarim (22:8), "If you build a new house, you shall make a fence for your roof, and you shall not bring bloodguilt into your house if somebody falls from it." This verse introduces the Torah obligation of "Ma’ake," to construct a fence around one’s roof to ensure that people who walk on the roof do not fall. One who fails to construct a fence neglects a Misvat Aseh (affirmative command) and also violates the Misvat Lo Ta’aseh (prohibition) of "Ve’lo Tasim Damim Be’betecha" ("you shall not bring bloodguilt into your house").
This obligation applies to roofs, porches or balconies that are used by people. For example, some houses have a porch that is higher than the ground, and people could get hurt if they fall off the sides of porch. Such a porch requires a fence or gate. Similarly, some people have a flat roof or balcony that they use for learning, eating or a Sukka. And some Yeshivot have large, flat rooftops that the students use for athletic activities. These, too, require a "Ma’ake." However, a slanted roof does not require a "Ma’ake," since people do not walk there.
How high must the fence be for the Misva to be fulfilled?
Halacha requires constructing a fence measuring ten Tefahim (handbreadths) high, but there are different views among the Halachic authorities regarding this measurement. According to some views, ten Tefahim is the equivalent of 80 cm, or 31.5 inches. The Hazon Ish (Rav Avraham Yeshaya Karelitz, 1879-1954), however, maintained that this measurement equals 97 cm, or 38.18 inches. Hacham Ovadia Yosef (listen to audio recording for precise citation) ruled that one should follow the stringent view of the Hazon Ish in this regard, given the severity with which Halacha treats matters involving physical danger ("Hamira Sakanta Me’isura").
More often than not, non-Jewish workers are hired to construct the fence or gate around one’s roof, porch or balcony. Preferably, though, one should personally make the final blow of the hammer, so that he can fulfill the Misva of constructing a "Ma’ake."
Summary: One is obligated to construct a fence or gate around any flat rooftop, balcony or porch in his home where people walk (as opposed to a slanted rooftop, which does not require a fence). The gate should be at least 38.18 inches high. If a non-Jewish worker installs the fence, the Jew should nevertheless make the final blow so that he can fulfill this Misva personally.
