Is it permissible to place a beam on a shared wall or a neighbor's wall if necessary for roofing?
General Chapter
Al-Mughni
Book of Settlement
Primary text
If there is a genuine need to place the beam on the neighbor's wall or a jointly owned wall, such that roofing is impossible without it, then placement is permissible without the partner's permission. This was the view of Shafi'i in his earlier position (Qadeem). The evidence for this is the Prophetic report mentioned earlier, and because it is a non-harmful usage of the neighbor's property, resembling leaning against it or seeking shade from it. This is distinguished from cultivation (zira'ah), which causes harm and is not necessitated.
Supporting text
Shafi'i in his later view (Jadeed), Abu Hanifa, and Malik state that it is not permissible, reasoning that it is an unauthorized use of another's property without dire necessity, analogous to cultivating the land. Furthermore, some scholars, like Al-Qadi and Abu Al-Khattab, stipulated permissibility only if the person needing to place the beam has three walls and the neighbor has only one wall. However, the sounder view relies solely on the necessity of roofing without the beam.