What happens if you skip the permit (and you needed one)
- Stop-work order issued by the city carries a $250–$500 fine, plus you'll owe double permit fees to legalize the work — total remediation cost $400–$1,200.
- Ledger board failure (common permit-skip outcome) causes water damage and structural rot; repair cost $5,000–$15,000 when mold enters the rim board, nearly always uninsurable after the fact.
- Home sale disclosure: Hazelwood requires unpermitted decks be disclosed to buyers; most lenders won't finance the purchase, and you'll be forced to tear it down or delay closing by 6-8 weeks for retroactive permitting.
- Liability: if someone is injured on an unpermitted deck, your homeowner's insurance will deny the claim ($50,000+ out-of-pocket exposure), citing code violation.
Hazelwood attached deck permits — the key details
Hazelwood adopts the 2021 International Residential Code (IRC) with amendments specific to Missouri's climate and geology. The core rule: IRC R507 governs all decks, and R105.2 explicitly exempts only freestanding decks that are under 200 square feet AND under 30 inches above grade AND have no stairs or railings. An attached deck — meaning one connected to your home by a ledger board — is never exempt, even if it's 100 square feet. The moment you tie it to the house, it becomes a structural alteration and requires a Building Permit from the Hazelwood Building Department. This distinction is critical: a ground-level floating patio with no attachment is fine. A 12-by-15 attached deck to your back door is not. The permit application will ask for your project valuation (deck cost estimate), deck dimensions, height above grade, footing details, and a site plan showing setbacks from property lines. For a typical 12-by-16 deck, expect a permit fee of $150–$300, calculated at roughly 1.5% of the project cost (a $15,000 deck pulls a $225 permit).
Footing depth in Hazelwood must reach 30 inches below finish grade — that's the frost line for this region. Your plans must show footings going down 36-42 inches (below frost line, with a safety margin) to below-grade concrete pads or piers. This is non-negotiable: the 30-inch frost line exists because Hazelwood's loess soil (a silt-clay mix laid down by glacial wind) expands when frozen and contracts on thaw, heaving shallow footings by 1-2 inches per winter cycle. Over three seasons, a 12-inch footing will sink, crack the deck frame, tear the ledger, and let water into the house rim board. The Building Department's plan reviewer will measure your footing detail against the frost line — show anything shallower than 30 inches and you'll get a red-mark request for revision. Use concrete footings with either a post-on-pad (simplest) or buried concrete piers. Some contractors skimp by digging only 18 inches because "it's just a deck." The inspector will catch it and require a re-dig. It costs $300–$800 more upfront to do footings right; it costs $8,000–$15,000 to replace a rotted rim board and ledger later.
The ledger board flashing is the second most-rejected detail in Hazelwood permit applications. IRC R507.9 requires a flashing that sheds water away from the house, not into it. The detail: flashing must be installed on top of the band board, wrapped over the rim, and nailed/sealed to the house's sheathing or rim joist — not nailed to the house's siding (siding moves and flexes; flashing can't). A drip edge below the flashing channels water away from the rim. Many DIY plans show flashing nailed into brick or vinyl siding; that fails. The code section is explicit: R507.9 requires a barrier between the ledger and band board, and the flashing must extend at least 4 inches up the wall and 2 inches down over the rim, with proper slope for drainage. Use EPDM rubber or metal flashing rated for wet locations. Galvanized flashing rusts in 15 years in the Midwest; use stainless or aluminum instead. The inspector will verify flashing detail at framing inspection, before decking is nailed down. If it's wrong, the deck is not approved for sheathing and you'll spend a week tearing decking off, fixing the ledger, and re-sheathing.
Hazelwood requires a 36-inch minimum guardrail height on any deck 30 inches or more above grade (some jurisdictions require 42 inches; Hazelwood uses the IRC baseline of 36 inches, measured from the deck surface). If your deck is 3.5 feet above ground, you need a guardrail. If it's 28 inches, you don't. Balusters (vertical pickets) must be spaced no more than 4 inches apart (a 4-inch sphere can't pass between them — this prevents toddler entrapment). Handrails are required on stairs only if the stairs have more than two risers; for a two-step stair, you don't need a handrail, but a guardrail is still required if the deck is 30+ inches high. Stair dimensions are tightly controlled by IRC R311.7: riser height 7-10.75 inches, tread depth minimum 10 inches. The inspector will bring a tape measure and check these at framing inspection. Undersized treads or uneven risers cause trips and rejections; plan ahead.
Attached decks in Hazelwood must also comply with setback and lot-coverage rules tied to your zoning district. Hazelwood's R-1 (single-family residential) zoning typically allows structures in rear yards with 10-15 feet clearance from property lines. Your deck can't encroach into a conservation easement or flood plain (if your lot is in a flood zone, FEMA rules override local code and may prohibit deck construction or require substantial elevation/floodproofing). The Building Department will check your deed and the county floodplain map before issuing a permit. If your property is in the 100-year floodplain, deck construction is either prohibited or requires a Conditional Use Permit from Hazelwood's Zoning Board, adding 4-6 weeks and $200–$500 to the timeline. Verify this early in the process by asking the permit technician if your address is in the floodplain — it's a free 5-minute phone call that can save you weeks of wasted planning.
Three Hazelwood deck (attached to house) scenarios
Hazelwood's frost line and soil behavior: why 30 inches matters for your footings
Hazelwood sits at the boundary of two soil types that both heave in winter. The city is built on loess (a fine silt deposited by glacial wind during the last ice age) in some areas and alluvium (river-deposited clay and sand) in others. Both expand when saturated and frozen; both expand by 3-5% as water turns to ice in the pores. The frost line — the depth at which soil stays frozen all winter — runs 30 inches in Hazelwood's climate zone (4A, St. Louis metro). Footings placed shallower than 30 inches will experience frost heave: the ground lifts the post 1-2 inches per winter, sinks back down in spring, and repeats. After three winters, a 12-inch footing will have moved 3-6 inches vertically, cracking the frame and tearing the ledger from the house.
The Building Department's plan review includes a frost-line check on footing detail. Show a footing at 18 inches depth and the reviewer will draw a red line and send it back. The required depth is 36-42 inches (frost line plus a 6-12-inch safety margin, so the excavation stays well below seasonal frost). Use concrete footings (concrete doesn't heave like soil does): either 12-inch diameter concrete piers, 12-by-12 concrete pads, or holes dug below frost line and filled with concrete to grade. Skipping this step costs $300–$800 more upfront but saves $8,000–$15,000 in remedial ledger and rim-board repair five years later.
The code reference is IRC R507.3: footing and foundation requirements for decks. Hazelwood enforces this strictly because failed deck footings don't just tip a deck — they pull the house's rim board away from the band, opening a gap where water pours into the rim, and rotting the framing that ties the foundation to the walls. Insurance doesn't cover this if it results from unpermitted work or code-noncompliant installation. Contractors who've built cheap in Hazelwood learn this lesson the hard way when they're called back to fix it at no charge, or sued by the homeowner three years later.
Ledger board flashing and water damage: the #1 reason attached decks fail in Hazelwood
The single most-common source of damage in Hazelwood attached decks is water pooling behind or under the ledger board. Rain hits the house wall, flows down the outside of the rim, and finds the gap between ledger and house. Over weeks and months, water wicks into the rim-board wood, freezes in winter, and begins to rot. By the time the homeowner notices (usually when the rim board is soft to the touch or the deck is pulling away from the house), the damage is extensive: $8,000–$15,000 in rim-board and band-board replacement, structural repair, and mold remediation. The Building Department's inspector will check ledger flashing detail at the framing inspection (after posts are set, ledger is attached, but before any decking is nailed down). If flashing is missing or installed incorrectly, the deck is not approved for decking installation, and you'll spend a week re-flashing and re-inspecting.
The code detail, per IRC R507.9, is specific: the flashing must be installed on top of the house's band board (not nailed to the siding; siding moves and flexes, flashing can't move with it). The flashing must be bent: 4 inches up the wall sheathing, 2 inches down the face of the rim, with a drip edge or lip that channels water away and down, not back toward the house. Use EPDM rubber membrane (easiest to install, most forgiving of imperfect framing) or stainless-steel flashing (more durable, requires careful bending). Galvanized steel rusts within 15 years in the Midwest; avoid it. The flashing must be sealed to the rim board with exterior-grade caulk (polyurethane or silicone; never use latex acrylic caulk, which fails in UV and freeze-thaw). Ledger bolts or lag bolts must pass through flashing, not alongside it, and bolts must be spaced 16 inches on center (IRC R507.9.2 specifies 1/2-inch bolts, 16-inch spacing, embedded 7 inches into rim board).
Hazelwood's plan reviewer will ask for a ledger detail showing flashing, bolts, caulk, and drip edge. Sketches showing flashing nailed to vinyl siding or omitting the drip edge will be rejected. Many online deck-plan repositories have substandard flashing details — if your plan looks like a generic download, expect a red mark. The inspector will verify the flashing at framing inspection, before decking is installed. If it's done right the first time, you save a week of re-work. If it's wrong, you'll be back at the job site with new flashing material, tearing off any partially-nailed decking, and calling the inspector again.
Hazelwood City Hall, Hazelwood, MO (verify at hazelwood.mo.us)
Phone: (314) 838-7387 (confirm with city website for Building Department extension) | https://www.hazelwood.mo.us/ (check for online permit portal link)
Monday-Friday, 8:00 AM - 5:00 PM (local time)
Common questions
Do I need a permit for a small deck in Hazelwood?
If it's attached to your house, yes — any size. If it's completely freestanding, under 200 square feet, and under 30 inches above grade, no permit is required. The moment you tie a ledger to your house, you need a permit. Verify your deck's classification with the Hazelwood Building Department before you start; a 10-minute phone call clarifies this.
How deep do deck footings need to go in Hazelwood?
36-42 inches below finished grade — that's the 30-inch frost line plus a 6-12-inch safety margin. Hazelwood's loess and alluvium soils heave in winter when frozen. Shallow footings settle and crack the deck frame, tear the ledger from the house, and cause water damage. Concrete footings (pads or piers) filled to grade are required; wood posts sitting directly in the ground are not code-compliant.
How much does a deck permit cost in Hazelwood?
Typically $150–$300, calculated at 1.5-2% of the project's valuation. A $12,000 deck pulls a $180–$240 permit. The fee covers plan review (10-14 days) and three inspections: footing pre-pour, framing, and final. You'll also pay for any electric or plumbing permits if your deck includes those — add $75–$125 per trade permit.
Can I build a deck myself in Hazelwood without hiring a contractor?
Yes, if it's your primary residence. Hazelwood allows owner-builder work on owner-occupied homes. You'll need to pull the permit yourself, submit plans, schedule inspections, and ensure the work meets code. Hiring a contractor doesn't change the permit requirement; you're just outsourcing the labor, not the permitting. Many homeowners pull their own permit to save the contractor's markup on permit fees.
What if my deck is in a flood zone? Do I need special approval?
If your property is in the 100-year floodplain, deck construction is either prohibited or requires elevation above the base flood elevation. FEMA rules override local code. Ask the Hazelwood Building Department to check your address against the floodplain map (free, 5-minute call) before you plan. If you're in a flood zone, you may need a Conditional Use Permit from the Zoning Board, adding 4-6 weeks and $200–$500 to the timeline.
Do I need a guardrail on my deck in Hazelwood?
Yes, if the deck is 30 inches or more above grade. The guardrail must be at least 36 inches high, measured from the deck surface. Balusters (vertical pickets) must be spaced no more than 4 inches apart to prevent toddler entrapment. If the deck is under 30 inches above grade, a guardrail is not required, but it's still a good safety practice.
How long does it take to get a deck permit in Hazelwood?
Plan review takes 10-14 days. Inspections (footing pre-pour, framing, final) typically turn around in 1-3 days each if you call promptly and schedule them. Total timeline from permit application to final approval: 4-5 weeks for a standard attached deck, or 8-10 weeks if your home is in a historic district (requires HPC approval first) or in a flood zone (requires Zoning Board review).
What happens if the inspector rejects my deck's ledger flashing?
The deck cannot be approved for decking installation until the flashing is corrected. You'll need to remove any partially-nailed decking, re-flash the ledger per IRC R507.9 (4 inches up the wall, 2 inches down the rim, with a drip edge and caulk), and call the inspector back. This adds 1-2 weeks to the timeline. Correct flashing detail on the first submission avoids this.
Can I add stairs or a ramp to my deck without a new permit?
If the stairs or ramp are part of the original deck permit application and plan, no — they're included in the single permit. If you've already received final approval on the deck and then want to add stairs later, you'll need to submit an amendment or a new permit. Adding stairs unpermitted after final approval will require a retroactive permit and re-inspection of the entire deck, at additional cost and delay.
Does Hazelwood require electrical or plumbing permits for a deck?
If your deck includes outdoor electrical outlets (GFCI-protected, per NEC 210.52), you'll need a separate electrical permit ($75–$125) and an electrical inspection. If you're adding a hot-tub line or water feature, a plumbing permit applies. These are filed separately from the deck permit; plan for additional review time and inspection. The Building Department can tell you what trades are needed based on your deck design.