Do I need a permit for an attached deck in
Montgomery, Illinois?

Montgomery attached deck permits—the key details

Montgomery requires a building permit for every deck attached to a house. The City of Montgomery Building Department enforces the 2021 International Building Code (IBC) and International Residential Code (IRC), which govern deck design, footing depth, ledger attachment, stair dimensions, and guardrail height. IRC R507 is the core rule: it mandates that deck framing be sized for live loads (40 psf for residential decks), that ledgers be flashed and bolted to the house rim board every 16 inches (per IRC R507.9), and that footings reach below the frost line. In Montgomery specifically, the frost depth requirement is 42 inches for the northern portions of the city (closer to the Chicago climate zone 5A boundary) and 36 inches for southern areas (zone 4A). This is not a negotiable guideline—footings above frost depth will fail inspection and must be re-dug. The ledger flashing detail is where Montgomery's building department most often rejects initial submissions. The code requires a drip-edge cap above the ledger, flashing underneath that directs water away from the rim board, and bolts spaced 16 inches on center. Many homeowners and even some contractors install ledgers without this flashing or with improper cap details, and Montgomery inspectors catch it every time.

Guardrails and stair dimensions are the second major compliance point. Any deck more than 30 inches above grade must have a guardrail at least 36 inches tall (measured from the deck surface to the top of the rail). Montgomery's code follows the IRC standard: balusters (the vertical spindles) must not allow a 4-inch sphere to pass between them, and the guardrail must be able to withstand a 200-pound horizontal force without deflecting more than 1 inch. Stairs must have a consistent rise and run (IRC R311.7.3 specifies rises no more than 7.75 inches and treads at least 10 inches deep), and stringers—the diagonal framing—must be properly cut and bolted to both the deck and the landing below. Open stairways (no handrails on both sides) require at least one handrail, and stringers cannot be notched more than 25 percent of their depth. Deck stairs are one of the most common failure points in inspections nationwide, and Montgomery's inspector is thorough. If your stairs are even a quarter-inch off in rise or tread, the inspector will flag it.

Footing and post details are the foundation of compliance. IRC R507.2 requires that deck posts sit on footings that extend below the frost line and rest on undisturbed soil or compacted fill. In Montgomery's glacial-till soils (common throughout the northern and central city), footings must be drilled or dug at least 42 inches deep in the north and 36 inches in the south, and the hole must be wider at the bottom (bell-shaped) to prevent frost heave. Posts must rest on a concrete pier, not directly on soil. Beam-to-post connections must use approved connectors—typically Simpson Strong-Tie hardware (e.g., post bases, joist hangers, lateral tie-down straps)—and bolts or nails must be sized per the connector's specifications and the lumber grade (pressure-treated pine UC4B is the standard). The city's plan review will examine your foundation design closely, especially if you're building in areas with known groundwater or clay soils. Any deck wider than 12 feet or longer than 16 feet should include a center beam with posts, not just perimeter posts, to prevent sagging. Montgomery's inspector will verify that beams are properly sized (typically 2x10 or 2x12, depending on span and snow load) and that posts are not undersized.

Owner-builder decks are permitted in Montgomery for owner-occupied residential properties. You do not need a licensed contractor to pull the permit if you are the owner and will do the work yourself. However, you must still submit plans (either hand-drawn to scale or from a pre-made deck design service) that show footing depth, ledger detail, guardrail height, stair dimensions, beam sizing, and post locations. Plans do not need to be stamped by a professional engineer for decks under 200 square feet or those without unusual loads (e.g., a hot tub), but they must be accurate and to scale. Many homeowners use simple sketches or purchased deck plans from retailers like Lowes or Home Depot, which are often accepted by Montgomery's building department—but always call ahead to confirm. The city's building department staff are usually available by phone during business hours (Monday-Friday, 8 AM to 5 PM) and can advise whether your plans meet the minimum submission standard or if you need to hire a designer.

Permit fees for attached decks in Montgomery are typically calculated as a percentage of the estimated construction cost (called the 'permit valuation'). A 12x16 deck (192 square feet) in Montgomery usually incurs permit fees of $200–$400, depending on whether it includes stairs, electrical, or plumbing. A larger 16x20 deck (320 square feet) might cost $350–$600. Permit fees typically run 1.5-2 percent of valuation, and the city charges an additional plan-review fee (usually $50–$150) if plans are submitted in person. The city does accept owner-builder applications, but does not waive inspection fees; you will owe inspection costs for footing pre-pour, framing, and final approval, typically $75–$150 per inspection. Once the permit is issued, you have one year to complete the work; after that, you must renew the permit (an additional fee, usually 10-20 percent of the original). Most attached-deck projects in Montgomery take 2-3 weeks from plan submission to permit issuance, assuming no major code issues are flagged on first review.

Three Montgomery deck (attached to house) scenarios