The Mishnah taught: R. Yosi says - The house owner must give the ceiling and the attic and the attic owner must give the mud.

R. Yusta citing Reish Lakish: The house owner gives the ceiling and the boards and the attic owner gives the mud (that is put between the boards).

Question: What type of mud must he give?

R. Yaakov bar Acha citing R. Elazar: Thick mud (to prevent water seeping through).

R. Abahu citing R. Elazar: Mud of medium thickness.

This is true when (the only time they use water in the attic) is to wash cups; but if they wash clothes there, even R. Abahu citing R. Elazar agrees that he must supply thick mud.

R. Chaninah instructed to these two Tziporians that both of them (i.e. even the attic dweller) should supply the ceiling and the boards, because the attic owner sometimes brings up the donkey drivers that come with their grains.

(Mishnah): If a house and its attic belonged to two and it fell down and the attic owner told the house owner to build and he refused, the attic owner can build a house (there) and live in it until he is given his expenses.

R. Yehudah: The attic owner is living in the space of the house owner so he must certainly pay him for the rental. Rather, the house owner must build the house and the attic and roof the attic and he may live in the house until the house owner pays his expenses. (Note: According to the Bavli, the second sentence begins with 'Rather, the attic owner must build...'.)

(Gemara) - Question: If the house owner wants to build but the attic owner does not, could the house owner say (that even if he does not want to build, but at least) he should seal up the roof?

Answer (Beraisa): If Reuven's fallen house was close to that of his partner Shimon and Shimon rebuilt his house and their dividing wall without permission; when Reuven will come to rebuild his own house, he should pay for his half of the dividing wall according to the price when the neighbor built it.

This shows that he cannot obligate the other partner to build the dividing wall without repaying him for it when he builds his own house. If so, the house owner cannot obligated the attic owner to seal up the roof unless he will repay him.