Building Permit Requirements in Illinois

Most Illinois cities require a building permit for decks more than 30 inches above finished grade or larger than 200 square feet. Ground-level decks that stay below both thresholds are often exempt from permits, though setback and zoning requirements still apply. Since the statewide baseline code took effect in 2025, even smaller communities that previously lacked building codes must now follow IRC standards for deck construction, which means the 30-inch threshold has become more universally applicable across the state.

Chicago applies its own municipal code, which imposes stricter requirements for deck construction including additional fire-resistance standards for decks on multi-unit buildings and specific requirements for the connection between decks and masonry walls. The city's tragic history with porch and deck collapses led to enhanced structural requirements that go beyond what the IRC requires. Joliet follows the IRC more closely and permits decks through its standard building permit process with fees based on project valuation.

Plan on submitting a site plan showing the deck's position on your lot relative to property lines and other structures, construction drawings with dimensions and structural details, and information about the foundation system including footing type and depth. Illinois frost depth varies from about 36 inches in the southern part of the state to 42 inches or more in the northern counties, and footings must extend below this line. Review times range from 5 to 15 business days in most jurisdictions, though Chicago's process can run longer for complex projects or properties in designated districts. Permit fees typically range from $75 to $350.

Fence permit requirements vary across Illinois cities, but most allow fences up to 6 feet in rear and side yards without a permit. Front yard fences are typically limited to 4 feet. When a fence exceeds the local height limit, a permit is usually required. Masonry and stone fences may trigger additional structural review requirements regardless of height because of the foundation and wind-load considerations involved.

Chicago requires a fence permit for any fence over 5 feet tall, which is slightly more restrictive than the 6-foot standard common in most suburbs. The city also has specific requirements for fences along alleys and on corner lots where intersection visibility is a concern. Rockford generally follows the 6-foot rear yard rule but requires permits for fences on corner lots and has specific provisions for fences adjacent to commercial properties.

Even where no fence permit is required, setback rules, easement restrictions, and utility line locations can affect where you place your fence. Call 811 before digging to have underground utilities marked. If your property is in a neighborhood with a Homeowners Association (HOA), expect additional rules about materials, style, and color that go beyond what the city requires. Illinois suburbs, particularly in the collar counties around Chicago, have high rates of HOA governance, and HOA fence restrictions are often more limiting than city code. Always check both your city's zoning requirements and your HOA covenants before installing a fence.

Small storage sheds are among the most commonly exempt structures in Illinois. Most cities exempt sheds that are 120 square feet or smaller, single-story, and used only for storage with no electrical or plumbing connections. Some communities set the threshold at 100 square feet, while others allow up to 200 square feet before a permit is needed. The variation exists because each city's zoning code sets its own exemption limit within the framework of the building code.

Aurora exempts accessory structures under 120 square feet that meet standard setback requirements and don't exceed the lot's maximum accessory structure coverage. Naperville follows a similar approach but enforces stricter rules on shed placement within its residential zoning districts, particularly regarding rear yard coverage limits and the total number of accessory structures allowed per lot. In Naperville's R1 and R2 zoning districts, the combined footprint of all accessory structures cannot exceed a certain percentage of the rear yard.

Setback requirements apply to sheds even when a permit is not required. You generally cannot place a shed directly on a property line, and most Illinois cities require a minimum of 3 to 5 feet from side and rear boundaries. If your shed will include electrical wiring, plumbing, or a concrete slab foundation, a permit is almost always required regardless of size, because utility connections trigger building code requirements for electrical safety and plumbing compliance. Permit fees for small sheds are typically modest, often under $100.

A standard ground-level patio made of concrete, pavers, or flagstone does not typically require a building permit in most Illinois cities. Patios trigger permit requirements when they include a roof or cover structure, are elevated above grade, or incorporate electrical or plumbing work such as outdoor kitchens, gas fire pits, or built-in lighting. A covered patio attached to the house is treated as a structural addition and requires a building permit in virtually every jurisdiction, with plan review for structural adequacy, setbacks, and lot coverage.

Chicago requires permits for covered patios and enforces impervious surface limits that can be especially tight on smaller urban lots. The city's lot coverage maximums in many residential zones mean that adding a large paved patio could push a property over its allowable impervious surface percentage, potentially requiring a variance. Naperville also regulates covered patios and requires that outdoor structures meet the city's stormwater management standards. Naperville has been particularly attentive to stormwater since adopting updated drainage requirements, and a new patio that significantly increases runoff may trigger additional engineering review.

Fees for patio permits depend on the project's scope. A basic covered patio might cost $75 to $200 in permit fees, while a more elaborate outdoor living space with electrical, gas, and plumbing connections will run higher and require coordination of multiple trade permits. Illinois's freeze-thaw cycles make proper base preparation critical for concrete and paver patios. While base preparation isn't a permit issue, your building department may ask about drainage and grading during plan review for covered patio projects. Plan for 5 to 15 business days of review time in most jurisdictions.

Building a garage in Illinois almost always requires a building permit, whether the structure is attached or detached. Garages involve foundations, framing, roofing, and often electrical work, putting them well above the thresholds that exempt smaller projects. Most cities treat garages as accessory buildings subject to full plan review, including structural adequacy, fire separation (for attached garages), zoning compliance for setbacks and height, and electrical safety.

Chicago requires permits for all garage construction and applies its municipal code requirements, including fire-separation standards for attached garages and specific requirements for garages on lots with alley access, which is the predominant configuration in many Chicago neighborhoods. The city regulates garage placement, height, and materials, and a detached garage on a standard 25-foot lot requires careful planning to meet setback requirements. Joliet also requires full permits and applies setback rules that determine how close a detached garage can be to property lines and alley access points.

Expect to submit a complete set of plans including site layout, foundation design, structural framing, and electrical drawings. If the garage will include a workshop with 240-volt circuits or a vehicle charging station, a separate electrical permit is typically required. Permit fees for garages range from $200 to $500 or more depending on the city and project size. Illinois frost depth requirements mean footings must extend 36 to 42 inches below grade depending on your location in the state. Inspections at the foundation, framing, electrical rough-in, and final stages are standard.