A building permit is required if you erect, construct, enlarge, alter, repair, move, improve, convert, or demolish a building or structure. This includes not only building construction or remodeling, but also such things as mobile home placement, wood stove installation, or plumbing modifications.
A building permit is not required for the following residential structures:
Single-story detached structures used as tool and storage sheds, playhouses and similar uses - under 400 square feet of floor area, 6 feet away from existing buildings, and classified as "U" occupancies.