Halacha

הלכה א
כֹּתֶל חָצֵר הַמַּבְדִּיל בֵּין שְׁנֵי שֻׁתָּפִין שֶׁנָּפַל. יֵשׁ לְכָל אֶחָד מִשְּׁנֵיהֶם לָכֹף עַל חֲבֵרוֹ לִבְנוֹתוֹ עַד גֹּבַהּ אַרְבַּע אַמּוֹת כְּדֵי שֶׁלֹּא יִרְאוּ זֶה אֶת זֶה. אֲבָל יֶתֶר עַל אַרְבַּע אַמּוֹת אֵין מְחַיְּבִין אוֹתוֹ. רָצָה הָאֶחָד וְהִגְבִּיהַּ הַכֹּתֶל יוֹתֵר עַל אַרְבַּע אַמּוֹת. אִם בָּא חֲבֵרוֹ וּבָנָה כֹּתֶל אַחֵר גָּבוֹהַּ כְּנֶגֶד הַכֹּתֶל שֶׁבֵּינֵיהֶן מְחַיְּבִין אוֹתוֹ לִתֵּן חֶלְקוֹ בַּגֹּבַהּ שֶׁכְּנֶגֶד כָּתְלוֹ. כֵּיצַד. בָּנָה אֶחָד כֹּתֶל שֶׁבֵּינֵיהֶן וְהִגְבִּיהוֹ עֶשֶׂר אַמּוֹת וּבָא חֲבֵרוֹ וּבָנָה כֹּתֶל אַחֵר כְּנֶגְדּוֹ אוֹ בְּצִדּוֹ לַעֲשׂוֹת לוֹ בַּיִת וְהִגְבִּיהַּ הַכֹּתֶל הָאַחֵר שֵׁשׁ אַמּוֹת מְחַיְּבִין אוֹתוֹ לִתֵּן חֶלְקוֹ בִּשְׁתֵּי אַמּוֹת שֶׁמּוֹסִיף עַל אַרְבַּע אַמּוֹת שֶׁהֲרֵי נִרְאֶה מִמַּעֲשָׂיו שֶׁהוּא רוֹצֶה בָּהֶן. וְכֵן אִם חָקַק בְּרֹאשׁ הַכֹּתֶל שֶׁבֵּינֵיהֶן מָקוֹם לְהַנִּיחַ בּוֹ הַקּוֹרוֹת אוֹ שֶׁבָּנָה עָלָיו קוֹרָה גְּדוֹלָה שֶׁהַקּוֹרוֹת נִשְׁעָנִין עָלֶיהָ מְחַיְּבִין אוֹתוֹ לִתֵּן חֶלְקוֹ בְּשֵׁשׁ הָאַמּוֹת כֻּלָּן שֶׁהוֹסִיף חֲבֵרוֹ עַל הָאַרְבַּע אַמּוֹת אַף עַל פִּי שֶׁלֹּא בָּנָה כָּל הַכֹּתֶל שֶׁהֲרֵי גִּלָּה דַּעְתּוֹ שֶׁהוּא רוֹצֶה בְּכָל הַגֹּבַהּ הַזֶּה:
כסף משנה
1.
When a wall that separates between two partners falls, each of the partners may compel the other to share in its construction until it reaches the height of four cubits, so that they will not see each other. We do not, however, compel a partner to build it any higher than four cubits.
The following rule applies if one of the partners takes the initiative and builds the wall higher than four cubits. If the other colleague comes and builds another wall of his as high as the wall between them, we obligate that partner to pay his share in the additional height that is opposite his wall.
What is implied? One person built a wall between himself and another partner and elevated it to a height of ten cubits. Afterwards, the other partner came and built another wall opposite it or at its side for the sake of making a room, and built that wall six cubits high. We obligate him to pay his share in the two cubits that were added to the minimum of four cubits. For it is obvious that he desired them.
Similarly, if he hewed out a place on the top of the wall between them to place beams or affixed permanently there a large beam on which the others rest, we obligate him to pay his share in the entire six cubits that his colleague added to the minimum of four cubits, although he did not build the entire wall. For he revealed his intent, that he desired the entire height of the wall.

הלכה ב
אֶחָד מִן הַשֻּׁתָּפִין שֶׁבָּנָה הַכֹּתֶל שֶׁמַּבְדִּיל בֵּינוֹ וּבֵין חֲבֵרוֹ עַד אַרְבַּע אַמּוֹת וְתָבַע חֲבֵרוֹ לִתֵּן חֶלְקוֹ בָּהוֹצָאָה וְאָמַר נָתַתִּי חֶלְקִי. הֲרֵי זֶה בְּחֶזְקַת שֶׁנָּתַן וְנִשְׁבָּע הֶסֵּת שֶׁנָּתַן וְנִפְטָר עַד שֶׁיָּבִיא רְאָיָה הַתּוֹבֵעַ שֶׁלֹּא נָתַן. אֲבָל אִם בָּא לִתְבֹּעַ אוֹתוֹ לִתֵּן חֶלְקוֹ בְּהוֹצָאַת שְׁאָר הַגֹּבַהּ שֶׁהוֹסִיף עַל אַרְבַּע אַמּוֹת מִפְּנֵי שֶׁסָּמַךְ לוֹ אוֹ כְּנֶגְדּוֹ וְאָמַר נָתַתִּי אֵינוֹ נֶאֱמָן. אֶלָּא חֲבֵרוֹ נִשְׁבָּע בִּנְקִיטַת חֵפֶץ שֶׁלֹּא נָתַן לוֹ וְנוֹטֵל מִמֶּנּוּ כְּדִין כָּל הַנִּשְׁבָּעִין וְנוֹטְלִין. עַד שֶׁיָּבִיא רְאָיָה זֶה שֶׁנָּתַן לוֹ:
כסף משנה
2.
The following rule applies when one of the partners builds a wall four cubits high that separates between his property and his colleague's property and demands that his colleague pay his share of the costs. If the other colleague claims to have paid his share, we assume that he paid. He is required to take a sh'vuat hesset that he paid, and he is then under no further obligation unless the plaintiff brings proof that he did not pay.
If, however, one partner demands of the other that he pay his share in the portion of the wall that he added above the minimum four cubits, because he built next to it or opposite it, and that partner claims to have paid, his statements are not believed. Instead, the plaintiff is given the option of taking an oath while holding a sacred article, that the defendant did not pay him. He may then expropriate the money, as is the case with regard to all those who take oaths and collect, unless the defendant brings proof that he paid him.

הלכה ג
מִי שֶׁהָיָה לוֹ חֻרְבָּה בֵּין חֻרְבּוֹת חֲבֵרוֹ וְעָמַד חֲבֵרוֹ וְגָדַר רוּחַ רִאשׁוֹנָה וּשְׁנִיָּה וּשְׁלִישִׁית עַד שֶׁנִּמְצֵאת חֻרְבָּה זוֹ מִשְּׁלֹשׁ רוּחוֹתֶיהָ גְּדוּרָה. אֵין מְחַיְּבִין אוֹתוֹ לִתֵּן לוֹ הַהוֹצָאָה כְּלוּם שֶׁהֲרֵי לֹא הוֹעִיל לוֹ וַהֲרֵי חֻרְבָּתוֹ פְּתוּחָה לִרְשׁוּת הָרַבִּים כְּשֶׁהָיְתָה. לְפִיכָךְ אִם גָּדַר לוֹ רוּחַ רְבִיעִית עַד שֶׁנִּמְצֵאת חֻרְבָּתוֹ מֻקֶּפֶת גָּדֵר מְגַלְגְּלִין עָלָיו אֶת הַכּל וְנוֹתֵן חֲצִי הַהוֹצָאָה שֶׁהוֹצִיא זֶה בְּאַרְבַּע רוּחוֹת עַד אַרְבַּע אַמּוֹת. וּבִלְבַד שֶׁיִּהְיֶה מְקוֹם הַכֹּתֶל שֶׁל שְׁנֵיהֶם:
כסף משנה
3.
The following rules apply when a person owns one ruin in the midst of several ruins belonging to a colleague. Although the colleague builds a divider on one side of the owner's ruin, and then on a second side, and then on a third side, and thus the ruin is enclosed from three sides, we do not obligate the owner to pay any of the costs. For the construction is of no benefit to him, since his ruin is still open to the public domain as it was before.
Therefore, if the builder also encloses the fourth side for him, and thus the owner's ruin is totally enclosed by a partition, we require him to pay his share in the entire amount. He must pay half the costs that his colleague undertook in building the divider four cubits high around all four sides. This applies provided the place of the wall belongs to both of them.

הלכה ד
אֲבָל אִם הָיָה הַכֹּתֶל שֶׁל זֶה שֶׁבָּנָה וּבְחֶלְקוֹ בָּנָה יֵרָאֶה לִי שֶׁאֵין מְגַלְגְּלִין עָלָיו אֶלָּא דָּבָר מוּעָט כְּמוֹ שֶׁיִּרְאוּ הַדַּיָּנִין שֶׁהֲרֵי אֵינוֹ יָכוֹל לְהִשְׁתַּמֵּשׁ בַּכְּתָלִים. וְכֵן אִם הַנִּקָּף עַצְמוֹ הוּא שֶׁגָּדַר רוּחַ רְבִיעִית הֲרֵי גִּלָּה דַּעְתּוֹ וְנוֹתֵן חֲצִי הַהוֹצָאָה שֶׁל שָׁלֹשׁ רוּחוֹת אִם הָיוּ הַכְּתָלִים שֶׁל שְׁנֵיהֶם. וְכֵן כָּל כַּיּוֹצֵא בָּזֶה:
כסף משנה
4.
If, however, the builder constructs the wall on his own property, it appears to me that the owner is charged only a small amount, as the judges see fit, because he does not have the right to use the walls.
If the person whose property was enclosed himself encloses the fourth side, he has revealed his consent and he must pay half the cost of the other three sides if the wall belongs to both of them. Similar principles apply in all analogous situations.

הלכה ה
וְכֵן שְׁנֵי בָּתִּים זֶה בְּצַד זֶה וְהָיוּ גַּגֵּיהֶן עֲשׂוּיִין לְדִירָה אֲפִלּוּ הָיוּ בִּשְׁנֵי צִדֵּי רְשׁוּת הָרַבִּים זֶה עוֹשֶׂה מַעֲקֶה לַחֲצִי גַּגּוֹ שֶׁהוּא דָּר בּוֹ וְזֶה עוֹשֶׂה מַעֲקֶה לַחֲצִי גַּגּוֹ. וְזֶה שֶׁלֹּא כְּנֶגֶד זֶה וּמַעֲדִיף כְּדֵי שֶׁלֹּא יִרְאוּ זֶה אֶת זֶה. וְאַף עַל פִּי שֶׁבְּנֵי רְשׁוּת הָרַבִּים רוֹאִין אוֹתוֹ יָכוֹל כָּל אֶחָד לוֹמַר לַחֲבֵרוֹ אֵלּוּ אֵין רוֹאִין אוֹתִי אֶלָּא בַּיּוֹם בְּעֵת שֶׁאֶעֱמֹד עַל גַּגִּי וְאַתָּה רוֹאֶה אוֹתִי תָּמִיד:
כסף משנה
5.
Principles similar to those that govern walls dividing courtyards apply to the construction of guard rails on roofs. If there are two houses situated next to each other, and their roofs are fit for use, one owner should make a guard rail for the half of the roof where he dwells, and the other should make a guard rail for the half of the roof where he dwells. They should extend the partitions beyond the midpoint, so that they will not see each other.
This applies even if the houses are built on two sides of the public domain. Although the people from the public domain can see the person on his roof, each one can tell his colleague: "The people in the public domain see me only during the day, when I stand on my roof. You, by contrast, see me at all times."

הלכה ו
גַּג הַסָּמוּךְ לַחֲצַר חֲבֵרוֹ עוֹשֶׂה לוֹ מַעֲקֶה גָּבוֹהַּ אַרְבַּע אַמּוֹת. אֲבָל בֵּין גַּג לְגַג מִשְּׁאָר הַגַּגִּין אֵינוֹ זָקוּק לְאַרְבַּע אַמּוֹת שֶׁאֵין בְּנֵי אָדָם דָּרִין בַּגַּגּוֹת לְפִיכָךְ אֵין בַּגַּגּוֹת הֶזֵּק רְאִיָּה. אֲבָל צָרִיךְ לַעֲשׂוֹת מְחִצָּה בֵּין שְׁנֵי הַגַּגִּין גְּבוֹהָה עֲשָׂרָה טְפָחִים כְּדֵי שֶׁיִּתְפֹּס אוֹתוֹ כְּגַנָּב אִם נִכְנַס לִרְשׁוּתוֹ:
כסף משנה
6.
When a person's roof is close to a courtyard belonging to a neighbor, he should build a guard rail four cubits high.
Between one roof and another, however, four cubits are not necessary. For people do not live on the roofs, and there is no concept of invasion of privacy. One must, nevertheless, make a divider ten handbreadths high between one roof and another to make a distinction, so that if one enters the other's property, it will be obvious that he is like a thief.

הלכה ז
שְׁתֵּי חֲצֵרוֹת זוֹ לְמַעְלָה מִזּוֹ לֹא יֹאמַר הָעֶלְיוֹן הֲרֵינִי בּוֹנֶה מִכְּנֶגְדִּי וְעוֹלֶה אֶלָּא בּוֹנִים שְׁנֵיהֶם מִלְּמַטָּה וְעוֹלֶה וּבוֹנֶה הָעֶלְיוֹן לְבַדּוֹ מִכְּנֶגְדּוֹ וָמַעְלָה. וְאִם הָיְתָה חֲצֵרוֹ לְמַעְלָה מִגַּגּוֹ שֶׁל חֲבֵרוֹ אֵין הָעֶלְיוֹן זָקוּק לַתַּחְתּוֹן כְּלָל:
כסף משנה
7.
When there are two courtyards, and one is situated above the other, the owner of the upper courtyard may not say: "I will build from my level and higher." Instead, both of them must share in the building from below upward, and the owner of the upper courtyard must build from his level and higher alone.
If a person's courtyard was higher than the roof belonging to a colleague, the owner of the higher property need not be concerned with the lower property at all.

הלכה ח
מִי שֶׁהָיָה כָּתְלוֹ סָמוּךְ לְגִנַּת חֲבֵרוֹ וְנָפַל כּוֹפִין אוֹתוֹ לְפַנּוֹת אֲבָנָיו. אָמַר לוֹ הִגִּיעוּךָ וַהֲרֵי הֵן שֶׁלְּךָ אֵין שׁוֹמְעִין לוֹ. וְאִם רָצָה בָּהֶן בַּעַל הַגִּנָּה וְאָמַר לוֹ הֵן אִם פִּנָּה אוֹתָם קָנָה וְאֵינוֹ יָכוֹל לַחְזֹר בּוֹ וַאֲפִלּוּ אָמַר הֵילָךְ יְצִיאוֹתֶיךָ וְאֶטּל אֲבָנַי אֵין שׁוֹמְעִין לוֹ. אֲבָל אִם לֹא פִּנָּה לֹא קָנָה שֶׁלֹּא אָמַר לוֹ אֶלָּא לִדְחוֹתוֹ:
כסף משנה
8.
When a wall belonging to a person that was located next to a garden belonging to a colleague falls, we compel the owner of the wall to remove his stones. If the owner of the wall tells the owner of the garden: "See, it came to you; they are yours," we do not heed him.
If, however, the owner of the garden desired the stones and agreed, saying "yes, " when he removes them, he acquires them. The owner of the wall may not retract. Even if he tells the owner of the garden: "Here is the money for your costs; let me take my stones," we do not heed him. If, however, the owner of the garden did not remove the stones, he does not acquire them. We assume that the owner of the wall made the statement only to procrastinate.

הלכה ט
חָמֵשׁ גִּנּוֹת הַמְסַפְּקוֹת מַיִם מִמַּעְיָן אֶחָד וְנִתְקַלְקֵל הַמַּעְיָן כֻּלָּן מְתַקְּנוֹת עִם הָעֶלְיוֹנָה. נִמְצֵאת הַתַּחְתּוֹנָה מְתַקֶּנֶת עִם כֻּלָּן וּמְתַקֶּנֶת לְעַצְמָהּ. וְהָרִאשׁוֹנָה אֵינָהּ מְתַקֶּנֶת עִם הַשְּׁנִיָּה וְלֹא מֵהַשְּׁנִיָּה וּלְמַטָּה. וְכֵן חָמֵשׁ חֲצֵרוֹת שֶׁשּׁוֹפְכִין מַיִם לְבִיב אֶחָד וְנִתְקַלְקֵל הַבִּיב כֻּלָּן מְתַקְּנוֹת עִם הַתַּחְתּוֹנָה. נִמְצֵאת הָעֶלְיוֹנָה מְתַקֶּנֶת עִם כֻּלָּן וּמְתַקֶּנֶת לְעַצְמָהּ וְהַתַּחְתּוֹנָה אֵינָהּ מְתַקֶּנֶת עִם הַשְּׁנִיָּה וְלֹא מִשְּׁנִיָּה וּלְמַעְלָה:
כסף משנה
9.
The following laws apply when there are five gardens that derive water from one spring, and the spring becomes impaired. All the owners of the gardens must share in the repairs made by the owner of the first garden. Thus the owner of the lowest garden must share in the repairs undertaken by all the others, but must make any repairs necessary in his own domain by himself. The owner of the first garden, by contrast, does not share in the repairs of the second, nor in any of those that are below him.
Similar laws apply when the inhabitants of five courtyards pour water into one drain, and the drain becomes damaged. All the inhabitants of the courtyards share in the repairs of the lower one. Thus, the inhabitants of the highest courtyard must share in the repairs undertaken by all the others, but must make any repairs necessary in his own domain by himself. The inhabitants of the lowest courtyard, by contrast, do not share in the repairs of the second, nor in any of those that are above it.

הלכה י
בְּנֵי הַנָּהָר מַשְׁקִין עַל הַסֵּדֶר. רָצָה אֶחָד מֵהֶן לִסְכֹּר כְּדֵי שֶׁיַּחֲזֹר לוֹ הַמַּיִם וְיַשְׁקֶה תְּחִלָּה וְאַחַר כָּךְ יִפְתַּח. וְאַחֵר רוֹצֶה לְהַשְׁקוֹת תְּחִלָּה. כָּל הַמִּתְגַּבֵּר זָכָה. וּבוֹר הַקָּרוֹב לָאַמָּה מִתְמַלֵּא רִאשׁוֹן מִפְּנֵי דַּרְכֵי שָׁלוֹם:
כסף משנה
10.
People with properties adjacent to a river who irrigate their fields with water from the river should do so in the sequence in which their properties are situated.
If one of the owners desired to dam up the river so that the water would flow through his property first, and only afterwards would he open it, and another owner wants the river to remain open so that his property will be irrigated first, whoever overcomes the other prevails.
When a cistern is close to an irrigation ditch, it can be filled first as an expression of "the ways of peace."

קניין הלכות שכנים פרק ג
Kinyan Shcheinim Chapter 3