Iowa Code § 563.4: Repairs — apportionment.

The repairs and rebuilding of walls in common are to be made at the expense of all who have a right to them, and in proportion to the interest of each therein, but every coproprietor of a wall in common may be exonerated from contributing to the same by giving up the coproprietor’s right in common, if no building belonging to that person is actually supported by such wall.