Reference for Bava Batra 118:9

לא מיבעיא קאמר לא מיבעיא לחצר חברו דלא אבל לחצר השותפין דא"ל סוף סוף הא קא בעית אצטנועי מינאי בחצר קא משמע לן דאמר ליה עד האידנא בחצר הוה בעינא אצטנועי מינך השתא אפילו בבית נמי בעינא אצטנועי מינך

<b><i>MISHNAH</i></b>. A MAN SHOULD NOT LET HIS WINDOWS OPEN ON TO A COURTYARD WHICH HE SHARES WITH OTHERS. IF HE TAKES A ROOM IN ANOTHER [ADJOINING] COURTYARD, HE SHOULD NOT MAKE AN ENTRANCE TO IT IN A COURTYARD WHICH HE SHARES WITH OTHERS. IF HE BUILDS AN UPPER CHAMBER OVER HIS HOUSE, HE SHOULD NOT MAKE THE ENTRANCE TO IT IN A COURTYARD WHICH HE SHARES WITH OTHERS. BUT HE MAY IF HE PLEASES MAKE AN INNER CHAMBER IN HIS HOUSE AND THEN BUILD AN UPPER CHAMBER OVER HIS HOUSE AND MAKE THE ENTRANCE FROM HIS HOUSE.<span class="x" onmousemove="('comment',' The reasons for all these rules are explained in the Gemara. ');">⁸</span>

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