Obligation to pay compensation (gharamah) if rebuilding is not compelled.
General Chapter
Al-Mughni
Book of Settlement
Primary text
If a co-owner refuses to rebuild, and the law does not compel him to do so (per the second report), he is not obligated to pay compensation or the value of the structure simply because the partner built it. This follows the principle that if he is not forced to build, he is certainly not forced to pay for its upkeep.
Supporting text
An exception exists if the refusing co-owner previously authorized the building and the expenditure; in such a case, he is obligated to pay what he authorized. Furthermore, if the builder rebuilt the wall intending to seek recourse (and did not merely offer it as a voluntary donation), there are two possible opinions on whether he can recover costs, dependent on the ruling regarding debt repayment without permission.