Do I need a permit for shed or accessory structure in Chicago?

It depends. Whether shed or accessory structure needs a permit in Chicago comes down to the details of your project.

Illinois has no single statewide shed threshold, so the 200 square foot figure quoted from the model International Residential Code does not govern here. Requirements are set by each municipality, and the ones we have checked are stricter than that figure: Wheaton does not require a building permit for a shed of 120 square feet or less, and Joliet requires a shed permit with a Residential Accessory Structures Review Form and a plat of survey showing the shed location. Assume the local number rather than a national one, and ask your building department for the threshold that applies at your address before you buy the shed. Zoning setbacks, easements and lot coverage still apply where no building permit is needed, and running electrical or plumbing to the shed triggers its own permit. A single-story detached shed, gazebo or playhouse up to 150 square feet in footprint, no taller than 15 feet, and with no plumbing, needs no building permit. Anything larger, or a detached frame garage, requires a permit (garages up to 600 sq ft use the Express Permit Program). The structure must comply with the Chicago Zoning Ordinance rules on accessory buildings and setbacks; a detached frame garage cannot have masonry walls, a flat roof, an upper level, heating equipment, or plumbing under the Express track. A licensed general contractor (Class A-E) is normally required for a permitted accessory building unless the owner qualifies to act as general contractor for their own primary residence.