Iowa Code § 563.3: Openings in walls.

No wall shall be built by any person partly on the land of another with any openings therein, and every separating wall between buildings shall, as high as the upper part of the first story, be presumed to be a wall in common, if there be no titles, proof, or mark to the contrary, and if any wall is erected which, under the provisions of this chapter, becomes, or may become, at the option of another, a wall in common, such person shall not be compelled to contribute to the expense of closing any openings therein, but this shall be done at the expense of the owner of such wall.