All Permit Guides

Do You Need a Permit for a Deck?

Almost certainly yes. Attached decks require a permit in virtually every jurisdiction in Illinois, Wisconsin, and Indiana. Even freestanding decks need permits if they're over 30 inches above grade or exceed 200 square feet. Decks involve structural engineering, frost-depth footings, and specific fastener requirements — and the inspections are strict.

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Free Deck Permit Check

Enter your address to find your building department, then answer a few questions to see if you likely need a permit.

What's an AHJ?

The specific city, village, or county office that issues permits. Their boundaries don't always match your mailing address.

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We cross-check your coordinates against municipal boundary polygons — not just ZIP codes.

Wrong AHJ = weeks lost

Filing with the wrong building department means your application sits unreviewed.

The Short Answer

If your deck is attached to your house, you need a permit. If it's freestanding but more than 30" off the ground or over 200 sq ft, you almost certainly need a permit. The building department will check footing depth, ledger board attachment, joist sizing, railing height, and stair dimensions. Deck collapses are a leading cause of residential structural failures — this is why inspections exist.

What Your Jurisdiction Checks

Footings & Frost Depth

Every deck post must sit on a footing that extends below the frost line. In Illinois, that's 42 inches deep. In Wisconsin, 48 inches. In Indiana, 36-42 inches depending on the county. Footings are typically 16-24" diameter concrete piers poured on undisturbed soil. This is inspected before you can pour concrete.

Ledger Board Attachment

The ledger board connects your deck to your house, and improper attachment is the #1 cause of deck collapses. Code requires lag bolts or through-bolts (not screws or nails) at specific spacing patterns. Flashing between the ledger and house siding is mandatory. You cannot attach a ledger to brick veneer alone, cantilevered floors, or engineered I-joists without manufacturer approval.

Structural Framing

Joist size, beam size, and post size all depend on span distances, spacing, lumber species, and grade. The IRC provides span tables (R507), but your AHJ may have adopted a different edition with different values. Post-to-beam connections must use approved hardware — no toe-nailing.

Guards & Railings

Required when the deck surface is more than 30 inches above grade. Minimum 36 inches tall (some jurisdictions require 42"). Balusters spaced no more than 4 inches apart (the "sphere test"). The top rail must resist 200 lbs of concentrated force.

Stairs

Maximum 7-3/4" rise per step, minimum 10" tread depth, minimum 36" width. Handrails required at 34-38" height with a graspable profile. Landings required at top and bottom.

Setbacks & Zoning

Decks usually must meet the same setbacks as your house. Some AHJs allow reduced setbacks for uncovered decks. Deck area may count toward lot coverage/impervious surface limits.

The Inspection Sequence

Most AHJs require three inspections for decks: a footing inspection (holes dug to depth, before concrete), a framing inspection (structure complete, before decking installed), and a final inspection (everything complete including railings and stairs).

State-Specific Notes

Illinois

Follows IRC with local amendments. Chicago has its own building code (not IRC-based). Most suburban AHJs use 2018 or 2021 IRC. 42" frost depth statewide.

Wisconsin

UDC (SPS 320-325) applies statewide for 1-2 family dwellings. 48" frost depth statewide — the deepest in the Permitech service area. State-controlled inspector licensing.

Indiana

No statewide residential building code. Each AHJ adopts its own (most use IRC 2012 or 2018). Frost depth varies 36-42" by county. Check your specific jurisdiction.

Common Deck Permit Mistakes

  1. 1Attaching the ledger board over siding instead of removing siding and flashing properly
  2. 2Using deck screws instead of structural bolts for the ledger connection
  3. 3Not digging footings to the full frost depth
  4. 4Exceeding joist span tables (undersized lumber for the span)
  5. 5Missing railings on elevated sections (any surface > 30" above grade)

Get Your Deck Permit Done Right the First Time

Deck permits are one of the most inspection-heavy residential projects. Our permit experts research every requirement for your specific address — frost depth, setbacks, structural requirements, and required documents — so your application is complete before you submit it.

Our automated permit packet currently covers sheds and garages. For deck permits, our Done-For-You team handles the complete research and document preparation.

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Tell us about your project and we'll send you a custom quote within 24 hours.

We'll review your project and respond within 24 hours. No spam, ever.

Deck Builders: One Subscription for Every Jurisdiction

You build decks across multiple cities and counties. Every one has different frost depths, setback rules, and code editions. Stop researching from scratch on every job.

Our self-serve subscription plans currently cover sheds and garages. For deck permits and other project types, we work with contractors on a custom contract basis tailored to your volume and service area. Fill out the quote form above and select "Contractor" — we'll put together a plan that fits your operation.

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Built by a former permit tech who processed 500+ building permits per year across IL, WI, and IN. We don't just check if you need a building permit — we check zoning too.

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