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Resolve the property
Match the address to its parcel, zoning context, and responsible permit authority.
What we check
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, not 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.
Process
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).
Per state
State-specific notes
IL
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.
Explore Illinois permit rules
WI
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.
Explore Wisconsin permit rules
IN
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.
Explore Indiana permit rulesWatch for these
Common deck permit mistakes
- Attaching the ledger board over siding instead of removing siding and flashing properly
- Using deck screws instead of structural bolts for the ledger connection
- Not digging footings to the full frost depth
- Exceeding joist span tables (undersized lumber for the span)
- Missing railings on elevated sections (any surface > 30" above grade)
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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 DIY Permit Package currently covers sheds and garages. For deck permits, our Done-For-You team handles the complete research and document preparation.
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For contractors
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", and we’ll put together a plan that fits your operation.
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