jointly owned by them all. The author is now discussing the case in which it belongs exclusively to one of them—that is, one of the two neighbours. Does the other have the right to place his beams upon this wall?

The author says: if there is a necessity, there is no objection; otherwise, he has no such right unless the owner gives permission. If the owner permits it, then it is permissible in all cases, whether or not there is a necessity, and whether or not it would harm the wall, because the wall belongs to the neighbour. Once he grants permission, there is no objection, and no one may prevent him from disposing of his property. But if he does not give permission, then the beams may not be placed upon it except subject to two conditions:

First: there must be a necessity to place them upon it.

Second: the wall must not be harmed by this.

His statement, “when he cannot roof [his building] except by means of it,” describes such necessity. For instance, the beams may be too short: if he were to roof the building using his own wall, the span would be too wide, and he would be unable to roof it because the beams are too short.

For example, a room is four metres long and two metres wide, with the width running along his neighbour’s wall. The beams he has are two and a half metres long. If he wished to lay the beams across the four-metre length, this would not be possible. Therefore, he must lay them across the two-metre width, and those two metres are along his neighbour’s wall. So we say: you may place the beams upon your neighbour’s wall, whether he agrees or not.

If it is asked, “Is there a condition for this?” we say: yes. The condition is that the wall must not be harmed thereby. For example, if the wall is thin and the beams are heavy, such that the wall would be harmed and there is fear that it may collapse, then he is not permitted to place them upon it, due to the Prophet’s saying: “There should be neither harm