We are beginning the fourth chapter of Tractate Bava Basra, with Mishnah 1. The topic of the next three Mishnayos is the scope of a sale: when a person sells a house and simply says, "This house is sold to you," without specifying exactly what is included in the sale - what is actually included? The Mishnah establishes its laws based on the norms, expectations, and ways houses were used in its era, which have little connection to the reality we know today, making it difficult to view them as practical halachah. Nevertheless, they teach us about the lifestyle of the Sages of the Mishnah and their perception of what is necessary for a residence.
Selling a house - what is not included in the sale:
"Hamocher es habayis lo machar es hayatzia" - one who sells the house has not sold the yatzia. The seller of the house, meaning the main living area, does not include the yatzia in the sale, which refers to the additions built around the house. This can be compared to an inner living area and an outer living area surrounding it: the inner one is used in the winter, as it is more insulated and warmer, while the outer one is used in the summer, when a person seeks fresh, cool air.
"Ve'af al pi shehi pesuchah lesocho" - and even though it opens into it. Even if the only access point to and from the yatzia passes through the main house, the sale includes only the four walls of the main living area, and the seller retains the rights to the outer house. This is true even if it means he will have to enter through the front door of the main house, like someone knocking on the door of the new owners.
"Velo es hacheder shelefnim himenu" - nor the room that is inside of it. This refers to an additional room, like a storage room, located further inside from the house. The setup is a structure where the courtyard is in the front, from the courtyard one enters the house, and behind the house - deeper inside - is the storage room. This room is not included in the sale of the house, as it is a separate unit, and the seller retains it for himself even though he sold the house itself.
"Velo es hagag" - nor the roof. The roof is also not included in the sale, as long as it was not explicitly stated that it is being sold with the house. People use their roofs for separate purposes: building a sukkah, drying fruit, and the like. There is a condition to this: "Bizman shiyesh lo ma'akeh gavoah asarah tefachim" - when it has a parapet ten handbreadths high.
The definition of a parapet:
The parapet (ma'akeh) is like a low wall or fence surrounding the edge of the roof. The Torah commanded its installation as a mitzvah - a safety fence protecting those who go up to the roof from falling. The existence of a parapet ten handbreadths high teaches that the roof is intended for access and use, and that it is a separate functional area independent of the main house. Therefore, one who sells his house has not sold the roof, since he intends to go up to it. The opposite is also implied: if the parapet is lower than ten handbreadths, the roof is not intended for use, and it is secondary to the main house and transfers with it in the sale.
The view of Rabbi Yehudah:
Rabbi Yehudah says: "Im yesh lo tzuras pesach, af al pi she'eino gavoah asarah tefachim, eino machur" - if it has the form of a doorway, even though it is not ten handbreadths high, it is not sold. If the access point leading up to the roof has the form of a doorway, an organized and formal entrance, there is no longer a need for a parapet ten handbreadths high. The very existence of such a doorway indicates that this is a separate and distinct area from the main house, and therefore the seller did not intend to include it in the sale - even if the roof was built improperly, lacking a parapet. The halachah does not follow Rabbi Yehudah.
In summary: One who sells a house without specification, without detailing the scope of the sale, has not sold the yatzia (even though it opens into the house), the room that is inside of it, and the roof that is surrounded by a parapet ten handbreadths high. The principle that emerges from here is: any area that serves a separate and independent use is not included in the sale, while what is secondary to the main house is sold with it. Rabbi Yehudah holds that even the form of a doorway alone is sufficient to consider the roof a separate area, but the halachah does not follow him.