Is it permissible to place a wooden beam upon a neighbor's wall?
General Chapter
Al-Mughni
Book of Settlement
Primary text
Placing a beam upon a neighbor's wall is forbidden if it causes damage to the wall due to its weakness in bearing the load. This is established without known dispute based on the Prophet's saying, 'There shall be no harm nor reciprocating harm' (Darrar wa la Dirar). If the placement causes no damage but the person could place the beam elsewhere, the majority of our companions and Shafi'i and Abu Thawr rule that it is impermissible, as it constitutes using another's property without permission and without necessity, similar to building a wall upon it.
Supporting text
Ibn Aqil indicated permissibility, citing the report from Abu Hurairah that the Messenger of Allah said, 'Let no one prevent his neighbor from placing his wood upon his wall,' which is agreed upon (Muttafaq 'alayh). Furthermore, what is permitted for general need does not require absolute necessity, evidenced by the right of preemption (shuf'ah), rescission due to choice or defect, keeping a dog for hunting, the allowance of advance sale (salaf), and concessions for travel.