Do I Need a Permit to Build a Deck in Illinois?

Illinois's new statewide building code

For decades, Illinois was one of the few states with no statewide building code. Each city and county was free to adopt whatever codes they chose — or no code at all. That changed on January 1, 2025, when Public Act 103-0510 took effect, requiring every municipality and county in the state to enforce building standards at least as strict as the International Residential Code (IRC).

The Illinois Capital Development Board oversees the new statewide requirements. Municipalities had until June 1, 2025 to confirm their local codes align with the baseline. Jurisdictions can enforce the 2018, 2021, or 2024 edition of the IRC, and they're free to adopt stricter standards — but they can no longer fall below the IRC minimum.

This is a significant shift for homeowners. Previously, some unincorporated areas and smaller communities had no building code enforcement at all, which meant no permit was needed for deck construction. Now, even those areas must meet IRC standards, though the law doesn't require municipalities that never had a building code to start enforcing one — builders and buyers in those communities are instead responsible for meeting the baseline code themselves.

Deck permit requirements vary significantly across the country — see our national deck permit guide for how Illinois compares to other states.

When you need a permit

Under the IRC baseline that now applies statewide, a building permit is required for most deck construction. The standard exemption — carried over from the IRC into most local codes — applies to decks that meet all of the following criteria:

• Freestanding (not attached to the dwelling)
• Not more than 30 inches above grade at any point
• Not larger than 200 square feet
• Does not serve the required exit door of the dwelling

If your deck fails any one of those conditions, you need a permit. In practice, most useful decks are attached to the house and accessed through a back door, which means most deck projects in Illinois require a permit.

Some municipalities go further than the IRC minimum. Naperville requires a permit for the construction of any elevated deck structure, and a separate permit is needed for replacement of structural or safety components on an existing deck — including beams, joists, stairs, or railings. Other suburbs in the Chicago metro area have similarly strict rules.

Beyond the building permit, many Illinois municipalities also require a zoning permit or zoning clearance before construction begins. This verifies that the deck meets setback requirements, lot coverage limits, and easement restrictions.

Chicago: the state's most complex permit process

Chicago operates under the Chicago Construction Codes, which are separate from the state building code and generally more complex. The city's Department of Buildings (DOB) handles all permit applications.

Chicago's permit system operates through the E-Plan online platform, and the minimum fee for any building permit that requires drawings is $302. Deck permits are calculated using a formula based on the deck's square footage, the construction type, and the applicable fee factor for the building it's attached to. For a typical residential deck, permit fees often land between $302 and $600, though larger or more complex projects can cost more.

The city offers several permit pathways. The Express Permit Program covers some minor renovation work and can be processed quickly, but most new deck construction goes through the Standard Plan Review process, which requires submitting architectural plans through E-Plan. Review times for standard plan submissions can range from several weeks to several months depending on the complexity and current volume.

Chicago also requires contractors to be properly licensed. Homeowners can pull their own permits for work on their primary residence, but if hiring a contractor, that contractor must be licensed with the city.

How cities outside Chicago differ

Aurora, the state's second-largest city, follows the IRC and requires permits for most deck construction. As part of the Fox Valley region, Aurora enforces standard setback requirements and requires a site plan showing the deck's position relative to property lines and easements.

Naperville is notably thorough. The city requires permits for any elevated deck structure and publishes a Residential Deck Resource Guide for homeowners. The deck permit fee in Naperville starts at $132, which includes a clerical fee, a minimum of two inspections, and the permit fee itself. The city's online Civic Access portal handles applications.

Joliet and Rockford both follow the IRC framework and require permits for deck construction that exceeds the standard exemption thresholds. Review times in these mid-size cities tend to be faster than in Chicago — typically one to three weeks for straightforward residential deck projects.

Springfield, the state capital, enforces the state building code and requires permits for deck construction. As a smaller city, Springfield's building department is generally responsive, with review times for simple residential projects often under two weeks.

Frost depth: Illinois's critical construction factor

Illinois sits squarely in the Midwest freeze zone, and frost depth is one of the most important factors in deck construction across the state. Deck footings must extend below the frost line to prevent heaving — when frozen ground expands and pushes improperly placed footings upward, it can crack concrete and shift the entire deck structure.

The typical frost depth in Illinois is 42 inches, though it varies by location. The Chicago metro area and central Illinois generally use a 42-inch minimum. Southern Illinois near the Kentucky border may have slightly shallower requirements, while the northernmost parts of the state can exceed 42 inches.

This means deck footings in Illinois are substantially deeper than in southern states like Georgia or Florida, where 12 to 18 inches is typical. The deeper footing requirement adds both labor and material cost to the foundation phase of deck construction — expect to dig holes roughly 48 inches deep (42 inches for frost depth plus clearance) for every support post.

Ground snow loads and structural design

Illinois also requires decks to be designed for ground snow loads, which vary across the state. Northern Illinois cities like Rockford and Chicago typically carry design snow loads of 25 to 30 pounds per square foot, while southern parts of the state may be lower.

Snow load affects the sizing of joists, beams, and footings — every structural member must support not just the 40 pounds per square foot live load (people, furniture) and 10 pounds per square foot dead load (the deck itself), but also the weight of accumulated snow. This is a design consideration that doesn't exist in Sun Belt states and directly impacts material choices and spacing.

Applying for a deck permit

Outside of Chicago, the process is handled by your local municipality's building department. Most Illinois cities require:

• A completed building permit application
• A site plan or plat of survey showing property boundaries, existing structures, easements, and the proposed deck location with distances to all property lines
• Construction drawings showing dimensions, framing layout, materials, joist and beam sizes and spacing, ledger board attachment details, footing locations, and railing specifications
• In some municipalities, the plat of survey must be signed and sealed by an Illinois registered surveyor and not more than five years old

Many suburban municipalities now accept applications through online portals. Naperville uses Civic Access, and several other cities have adopted digital submission systems.

Review times vary by municipality. Chicago can take weeks to months. Suburban communities in the collar counties typically process residential deck permits within one to three weeks. Smaller cities and county building departments may be faster — sometimes within a week for simple projects.

Fees outside of Chicago are generally lower. Most suburban and downstate municipalities charge between $75 and $300 for a residential deck permit, depending on the size and the municipality's fee schedule.

Inspections

Most Illinois municipalities require at least two inspections for deck construction: a footing inspection before concrete is poured, and a final inspection after the deck is complete. The footing inspection verifies that holes are dug to the proper depth (at or below the frost line), are properly sized, and are located in the correct positions per the approved plans.

Some municipalities add a framing inspection between the footing and final stages. At the framing inspection, the building official checks joist sizes and spacing, beam connections, ledger board attachment and flashing, and hardware.

At the final inspection, the inspector verifies that the completed deck matches the approved plans, guardrails meet height and baluster spacing requirements, stairs are properly built, and all structural connections are secure.

HOAs and additional requirements

Illinois has a significant number of Homeowners Associations (HOAs), particularly in the suburban collar counties around Chicago. If your property is in an HOA, you may need architectural approval from the HOA before applying for a building permit — and in some cases before you finalize your deck design.

HOA requirements are separate from and in addition to building code requirements. An HOA might restrict deck materials (requiring composite over pressure-treated wood, for example), limit the size or height of the deck, or mandate specific colors and finishes. Always check your HOA covenants before starting the permit process.

What happens if you skip the permit

Building a deck without a permit in Illinois carries real consequences. Municipal code enforcement can issue stop-work orders and fines, and you may be required to tear down unpermitted work or retrofit it to meet code — at your own expense.

In Chicago, the penalties are particularly steep. Working without a permit can result in fines of up to five times the normal permit fees, plus additional penalties. The city also charges a "working without a permit" surcharge on top of the standard fees when unpermitted work is discovered.

Beyond fines, unpermitted decks create problems when selling your home. Illinois real estate transactions routinely involve disclosure of permits, and an unpermitted deck can delay a sale, reduce the sale price, or require costly remediation before closing.

For an overview of all building permit requirements in Illinois — including sheds, fences, pools, and more — see our complete Illinois building permit guide.

If you're also planning a patio or fence alongside your deck, note that Illinois has separate permit requirements for each — see our guides to patio permits in Illinois and fence permits in Illinois.