Rambam - 1 Chapter a Day

If, however, the projection extends over a courtyard that is jointly owned by several people, this restriction does not apply [Tur, Shulchan Aruch (Choshen Mishpat 153:5)].

If there were no danger of the projection-owners invading the privacy of the owner of the courtyard, he would be allowed to make use of the empty space, for when one person will derive an advantage and the other will not suffer any loss, the person is granted the right to that advantage. (See Chapter 7, Halachah 8 and notes.) Nevertheless, this is not allowed in the present instance, for there is a real danger of loss of privacy.

And the owner of the courtyard cannot, at a later time, demand that the projection be removed.
As explained in Chapter 11, Halachah 4, and as mentioned in the notes on Chapter 7, Halachah 6, the projection-owner’s right is established immediately. He does not have to wait three years, nor must he produce a claim that legitimizes his construction of the projection. All that is necessary is for him to produce proof that the owner of the courtyard saw the projection and did not protest immediately. (See the Rambam’s Commentary on the Mishnah, Bava Batra 3:6.)
The Tur and the Ramah (Choshen Mishpat 153:2) differ and maintain that three years must pass before the owner of the projection establishes his right to it. They also maintain that if the projection is not more than a square handbreadth, the owner of the projection can never establish his right to use it. Indeed, the owner of the courtyard may himself use the projection and prevent the person who built it from using it.

For a square handbreadth is considered a space of significant size.

Although he has a right to use the projection whenever he desires, as stated in Halachah 1, he may not prevent the owner of the courtyard from building below it.

Sefer Me’irat Einayim 153:6 maintains that the owner of the courtyard may even have the projection removed entirely. Since it was never large enough to be significant, although the owner of the projection was given permission to use it while it existed, the courtyard owner may remove it whenever it becomes an obstruction to his own use of the courtyard space.

The Tur and the Ramah (Choshen Mishpat 153:4) state that the same laws apply when the projection is one handbreadth long and four handbreadths wide.

The Rashbam (Bava Batra 59b), the Maggid Mishneh, and the Sefer Me’irat Einayim 153:8 explain that a space one handbreadth by four handbreadths is very significant. Since the owner of the courtyard has consented to granting the owner of the projection a space this size, we assume that he was willing to grant him a space four handbreadths by four handbreadths.
The Ra’avad differs with the Rambam on this point and maintains that the owner of the projection must produce proof that the owner of the courtyard sold the right to extend a projection. This reflects the difference of opinion mentioned in the notes on Halachah 1.

Even if the projection is longer than four handbreadths, the owner of the projection is not entitled to make it more than four handbreadths wide (Rashbam loc. cit.).

The Maggid Mishneh states that the measure of 10 handbreadths was not mentioned in the Talmud. Nevertheless, it was accepted by our Rabbis, because that is a minimum size of a house.

This is the definition of the term, an Egyptian ladder, mentioned in the Mishnah, Bava Batra 3:6.

The Siftei Cohen 153:10 writes that a field is mentioned to teach us the definition of the term courtyard used in this instance: that we are not speaking of a courtyard used for personal use, for in such a place using the ladder would certainly be an invasion of privacy and the owner of the courtyard could prevent him from doing so, as he can prevent him from constructing a projection. Instead, the intent is a courtyard that is used like a field.

I.e., he places the ladder in his neighbor’s property and leans it up against the wall, so that he could climb up the ladder and gain access to his own property.

Since the ladder is small, we do not consider it as a matter of consequence, since the owner of the courtyard would not be bothered by its use. Therefore, the fact that he does not protest is not considered proof of his acceptance of the presence of the ladder.
The Ramah (Choshen Mishpat 153:13) states that if the owner of the ladder affixes the ladder with nails and the owner of the courtyard does not protest, he has established his right to the ladder, even if the ladder is small.

He may not, however, prevent the neighbor from placing the ladder there, as stated in the conclusion of the halachah.

This is the definition of the term, a ladder from Tyre, used in the Mishnah.

The Rambam follows his opinion – reflected in the previous halachot – that by not protesting the ladder’s presence when he first saw it, the owner of the courtyard acquiesced to its remaining there.
In this instance, as in the previous halachot, the Tur and the Ramah (Choshen Mishpat 153:16) maintain that it takes three years before the owner of the ladder establishes his right to maintain it. (See also Sefer Me’irat Einayim 153:32.)

For as mentioned above, it does not constitute an invasion of privacy.

As explained in Chapter 7, Halachah 8 and notes, not allowing such consideration is termed “the attribute of Sodom,” which our Sages would compel the Jews not to emulate.

Sefer Me’irat Einayim 153:15 states that this applies both to draining off rain water and to removing sewage water.

A larger pipe than the pipe mentioned in the first clause. In his Commentary on the Mishnah (Bava Batra 3:6), the Rambam states that this applies to a wooden gutter that extends over the entire length of a wall and then has the water flow down through a drainpipe. This is done in order to protect the wall from erosion by the water.

Because this concentrated flow of water could present a source of discomfort – and perhaps damage – to the owner of the courtyard.

As in the previous halachot, according to the Rambam, if the owner of the courtyard does not protest, the owner of the roof establishes his right to the drainpipe immediately. The Tur and the Ramah (Choshen Mishpat 153:6) maintain that it takes three years before the owner of the roof establishes his right to the drainpipe. See Sefer Me’irat Einayim 153:32.

If, however, the owner of the roof removes the drainpipe, and the owner of the courtyard does not protest, he is considered to have waived his right to the water [Ramah (loc. cit.)].

For he could make positive use of the water that flows into his courtyard.

On the same side (Meiri).

Moreover, the owner of the courtyard may not move the pipe anywhere if doing so inconveniences the owner of the roof [Ramah (Choshen Mishpat 153:8)].

The Maggid Mishneh explains that all the structural changes mentioned in this halachah do not increase the quantity of water flowing into the neighbor’s courtyard; they merely alter the rate at which the water flows in. If, however, he makes changes that increase the quantity of water that flows into the courtyard, his neighbor may protest. See Shulchan Aruch (Choshen Mishpat 153:11).

Even if one of the neighbors refrains from inserting beams for a long period of time, he does not forfeit his right to do so [Ramah (Choshen Mishpat153:14)].

With this phrase, the Rambam clarifies two points:
a) that the beams may be inserted more than half-way across the wall, indicating that the two are considered partners in the entire wall. It is not that half belongs to one and the other half to the other.
b) that their weight is not a factor. The Ramah (Choshen Mishpat 153:14) infers that in this regard there is a restriction. The beams may not be heavier than what is ordinary for that region.

For using the wall for any purpose may detract from its strength.

Here the term is not being used in the ritual sense, but rather as a reference to a structure similar to that used on the holiday, but employed for shade in the summer.

I.e., although he had a right to protest, he did not exercise it as long as he thought that the structure was only temporary and thus would not cause lasting damage to his wall.

For the owner of the wall was obviously doing him a favor and allowing him to make use of the wall for the holiday. The owner of the wall may require him to remove the beam during the holiday as well.

Actually eight days, for he is forbidden to remove the sukkah on Shemini Atzeret, the holiday that follows the seven days of Sukkot. In the diaspora, this also applies on Simchat Torah, the holiday that extends Shemini Atzeret in the diaspora. Moreover, if Simchat Torah is followed by the Sabbath, an additional day is granted.

For once the sukkah is left beyond the time when it is necessary for ritual purpose, the owner of the beam is making it obvious that his use of the wall is not merely a temporary matter.

For this is clearly a sign that he intended to leave the beam there permanently.

This shows that he consents to his use of the beam.

In this halachah, the Rambam follows the approach reflected in the previous halachot, that even though the person who inserted the beam is overstepping his rights, if the other neighbor does not object, the person establishes his right to the use of the property immediately. In this instance as well, the Tur and the Ramah (Choshen Mishpat 153:16) differ and maintain that it takes three years before the owner of the beam establishes his right to maintain it. (See also Sefer Me’irat Einayim 153:32.)
The Tur also maintains that if the owner of the beam admits that the wall belongs to the other colleague, he must also claim to have purchased the right to place his beam in the wall from his colleague.

This law is not explicitly stated in the Talmud. Nevertheless, from the fact that there is a difference of opinion (Bava Batra 6a) with regard to whether one may replace a lighter beam with a heavier one, we may conclude that although the Rambam follows the more lenient opinion in that instance (see the previous halachah), the leniency has its limits (Maggid Mishneh).

Although the other person protests and claims that he is the owner of the entire wall, unless there are witnesses, we accept the claim of the owner of the beams for the reason the Rambam continues to explain.

This is accepted as proof of his partnership in the wall. For had the other owner been the sole owner of the wall, it is unlikely that he would have let him insert his beam into the wall.

His word is accepted regardless of the amount of time his beams had been inserted into the wall. There is no need for them to remain there three years (Maggid Mishneh).
The Maggid Mishneh explains that this ruling is also not explicitly stated in the Talmud and is the product of the Rambam’s deductive reasoning. The Maggid Mishneh, however, questions the conclusion, noting that there are authorities (Rabbenu Tam, Rabbenu Asher, as reflected in the rulings of the Tur and Sefer Me’irat Einayim 153:36) who require that the person who inserted the one beam have had that beam inserted for at least three years.
The Maggid Mishneh explains that the Rambam’s ruling (and that of Rabbenu Asher, who accepts such a claim if made after three years) applies only when the person claims that he was a partner in the construction of the wall from the very beginning, but until this time, he had not desired to use it for his beams. If, however, he admits that it was his colleague who constructed the wall originally, the fact that he inserted a beam [or beams] there is of no consequence unless he built a roof. Nevertheless, as the Kessef Mishneh and the Ramah (Choshen Mishpat 153:18) indicate, this interpretation is not accepted by all authorities. The Tur maintains that if a person’s beams are inserted into a wall, we accept his claim to partnership in the ownership of the wall even if he admits that he did not originally build the wall, but merely purchased (or was given) a share in it afterwards. In such an instance, should the wall fall, he receives half of the stones of the wall, but not half of the land on which it was built.

Since he does not have witnesses to support his claim, the oath is required to prove the integrity of his claim. Compare to Hilchot To’en V’Nit’an 11:1.

The Kessef Mishneh quotes two responsa from the Rivash that state that when neither the ownership of a wall nor the identity of the party who built it is known, the fact that one person has many beams inserted into it and the other bas only one or none is not considered proof of ownership.

I.e., if the spaces for the beams were to be hollowed out while the wall was standing, that would shake the wall and make it less sturdy.