Reference for Bava Batra 4:1
הַמּוֹכֵר אֶת הַבַּיִת, לֹא מָכַר הַיָּצִיעַ, וְאַף עַל פִּי שֶׁהִיא פְתוּחָה לְתוֹכוֹ, וְלֹא אֶת הַחֶדֶר שֶׁלִּפְנִים מִמֶּנּוּ, וְלֹא אֶת הַגַּג בִּזְמַן שֶׁיֶּשׁ לוֹ מַעֲקֶה גָבוֹהַּ עֲשָׂרָה טְפָחִים. רַבִּי יְהוּדָה אוֹמֵר, אִם יֶשׁ לוֹ צוּרַת פֶּתַח, אַף עַל פִּי שֶׁאֵינוֹ גָבוֹהַּ עֲשָׂרָה טְפָחִים, אֵינוֹ מָכוּר:
One who sells a house has not sold the yatzia, even if it opens into it. [A yatzia is a kind of room running around the walls of the house from the outside, as in the Temple, viz. (I Kings 6:6): "…and the nethermost yatzia." Some build it in the thickness of the wall. And even if it opens into the house and is utilized therefrom, still, it is not (regarded as) sold (with it). This, if it contains four cubits; but if not, it is not regarded as distinct (from the house)]. And (he has) not (sold) the room before it, [the house, even if it opens into the house and communicates with it.] And (he has) not (sold) the roof when it has a railing ten handbreadths high, [in which instance it is distinct in itself and not "absorbed" in the house.] R. Yehudah says: If it has the configuration of a door, even if it is not ten handbreadths high, it is not sold. [The halachah is not in accordance with R. Yehudah.]