What happens if you skip the permit (and you needed one)
- O'Fallon Building Department issues stop-work orders ($500–$1,500 fine) if a neighbor or inspector discovers unpermitted work; re-pulling a permit after the fact doubles the fee ($300–$600 total).
- Insurance claim denial: most homeowner policies exclude damage to unpermitted roof work, and if a leak or hail damage occurs post-replacement, you're out of pocket for repairs.
- Refinance or home-equity loan blocked: lenders order title-search and final inspection records; missing permit on recent roof work kills approval (typical cost to re-inspect and re-permit: $400–$800).
- Disclosure hit on resale: Missouri requires disclosure of unpermitted alterations to the roof structure; buyer can sue for misrepresentation or demand a credit ($3,000–$15,000 depending on negotiation).
O'Fallon roof replacement permits—the key details
O'Fallon follows the 2021 International Residential Code (or the IRC cycle in effect at the time of your permit submission). The core rule is IRC R907.4: if your roof already has two or more layers of shingles, you must tear off all existing material before installing new shingles. This applies whether you're replacing 50% or 100% of the roof. The City of O'Fallon Building Department does not grant overlays on 3rd-layer roofs, period. Why? Codes assume that a third layer adds excessive dead load and degrades fastener holding power into the deck, creating a collapse risk in high wind or heavy snow. O'Fallon sits in St. Louis's metro area where many homes were reroofed in the 1990s and again in the 2010s without tear-offs—so this rule is actively enforced. Before you pull a permit, count the layers in your attic or have a roofer inspect from inside. If you find three layers, budget for full tear-off labor (typically $500–$1,500 extra) and plan 2–3 extra days on the job.
Underlayment and fastening are the biggest sticking points in O'Fallon's plan review. The permit application requires you (or your contractor) to specify the underlayment type—synthetic (preferred, ~$0.30–$0.50/sq ft) or felt (older standard, ~$0.10/sq ft)—and the fastening pattern (nails per shingle, spacing, head size). For asphalt shingles, O'Fallon expects 6 fasteners per tab (ASTM D3161 standard) minimum. If you submit a permit application that doesn't name the underlayment or fastening spec, it will be rejected with a comment like 'Specify manufacturer and type of underlayment per IRC R905.2.3(a) and confirm fastener count.' In practice, most contractors pre-fill this correctly, but owner-builders often miss it. Climate Zone 4A also mandates ice-and-water shield (self-adhering membrane) starting at the edge of the roof and extending up at least 24 inches from the exterior wall line, or to a point 2 feet inside the warm-wall plane if you're in an unheated attic. Get the exact requirement from the city before you order materials.
Structural deck inspection is mandatory for any tear-off. Once the old shingles come off, O'Fallon Building Department (or their third-party inspector) will schedule a deck-nailing inspection before new underlayment goes down. They're checking for rot, prior improper repairs, and adequate fastening of the deck sheathing itself (typically 1/2-inch CDX plywood or 1x6 lumber boards). If the deck is damaged, you'll need repair estimates and a revised permit scope. This inspection is included in the permit fee but adds 3–5 business days to your timeline; plan around it. Some contractors schedule it on a Friday and re-start Monday, which doubles the job duration. Budget for this upfront in your timeline.
Material change—for example, switching from asphalt shingles to metal, stone-coated steel, or tile—requires a separate structural review, particularly for tile. O'Fallon will demand that you submit a structural engineer's letter confirming the deck can handle the additional dead load (tile can be 700–900 lbs per square vs. asphalt at ~400 lbs per square). This adds $300–$600 to soft costs and 1–2 weeks to the permit review. Metal or stone-coated steel are lighter and usually pass without engineering, but the City of O'Fallon's permit form will ask you to confirm the roof load rating; make sure your contractor provides the product spec sheet.
Owner-builder rules: O'Fallon allows owner-occupants to pull owner-builder permits and perform their own roof work IF the property is primary residence and there is no lien holder objection. However, the practical reality is that roofing is one of the few trades where insurability and contractor-license verification are stringent. Your homeowner's policy may not cover roof work you do yourself, and O'Fallon's final inspection is strict on fastening and underlayment detailing. Unless you have roofing experience and are comfortable with fall protection, hiring a licensed contractor ($5,000–$12,000 for asphalt) is strongly recommended. If you do self-perform, confirm with your homeowner's insurer that the work is covered and pull the permit yourself through O'Fallon's online portal or in person at City Hall.
Three O'Fallon roof replacement scenarios
Why O'Fallon enforces the 3-layer tear-off rule so strictly
The St. Louis metro area, including O'Fallon, has a specific roofing history. Many homes built in the 1960s–1980s had original asphalt shingles. In the 1995–2005 boom, roofers applied overlay after overlay without tearoff, partly because labor was cheap and homeowners were cost-sensitive. By 2010–2015, third and sometimes fourth layers were common. Meanwhile, climate events (summer hail, occasional ice dams in winter, and spring convective storms) accelerated shingle failure. O'Fallon Building Department found that multi-layer roofs leaked sooner, developed rot in decks, and required emergency tear-offs under storm damage. IRC R907.4 codified the 'no 3rd layer' rule nationally in 2006, and O'Fallon adopted it to prevent the costly aftermath: homeowner complaints, insurance claims, and structural repairs.
From a code perspective, the deck cannot be inspected properly if shingles are overlaid, meaning rot, previous poor repairs, and fastener rust go undetected. Additionally, weight accumulation (three layers of shingles + ice + snow can exceed 1,500 lbs per square) exceeds design loads on older trusses and rafters, increasing collapse risk. The fastening pattern also degrades: the second layer's fasteners sometimes miss the deck entirely (hitting only the first layer), and the third layer's fasteners miss everything. O'Fallon inspectors have seen deck failures traced directly to overlaid roofs after heavy snow events. Enforcing the tearoff rule prevents that liability.
On a practical note, the tearoff cost ($1,500–$2,500 depending on roof size and debris disposal) is a bitter pill, but homeowners who comply avoid far worse costs later: a mid-winter roof leak in a multi-layer configuration can cost $5,000–$20,000 in water damage, mold remediation, and emergency repairs. O'Fallon's stance is: pay the tearoff cost now, or pay the damage cost later. When you pull your permit, accept the tearoff as part of the plan.
Climate Zone 4A roofing details: ice-and-water shield, fastening, and the 30-inch freeze line
O'Fallon is in IECC Climate Zone 4A (cool temperate). Winters see temperatures dipping below freezing (average low in January is ~27°F, with occasional lows below 0°F) and snow accumulation of 10–20 inches most years. This climate demands ice-and-water shield (self-adhering synthetic membrane) along the eaves and gutter line to prevent ice dams and the backup leaks that result when snow melts and refreezes at the cold roof edge. IRC R905.1.2(a) requires the shield to extend at least 24 inches up from the exterior wall line (or 2 feet inside the interior wall plane if the attic is unheated), whichever is greater. For most O'Fallon homes with uninsulated attics or minimal attic insulation, the 24-inch-from-eaves rule applies. On a 30-foot-wide ranch, that's roughly 3 squares of ice-and-water shield at ~$35–$50 per square.
Why this depth? When snow sits on a cold roof and the attic is unheated, melt happens only at the eaves (the coldest part, furthest from interior heat). The liquid water runs down and hits the edge, where it refreezes, creating a dam. Water backs up behind the dam and soaks into the substrate. The self-adhering membrane seals any nail or fastener hole, allowing the water to drain harmlessly over the edge rather than penetrate the deck. O'Fallon inspectors verify this at final by checking that the ice-and-water shield is indeed installed and extends the full distance; they may even ask for product documentation confirming it meets ASTM D1970 (the standard for self-adhering roofing membranes).
Fastening requirements also shift slightly in cold climates. Asphalt shingles require 6 fasteners per tab (roughly 2 inches below the cutline); in Zone 4A, some conservative contractors use 8 fasteners, but 6 is code-compliant. However, fasteners must be galvanized or stainless (not bare steel) because of the freeze-thaw cycle and occasional moisture. O'Fallon doesn't explicitly require this in the code text, but inspectors understand it—if you use bare-steel fasteners and come back 5 years later with rust staining and leaks, the inspector will note it at final. Ask your contractor: are the nails hot-dipped galvanized or stainless? They should cost roughly $0.02–$0.04 more per nail but are non-negotiable in Zone 4A.
O'Fallon City Hall, O'Fallon, MO 63366
Phone: (636) 272-1550 | https://www.ofallon.mo.us/permits
Monday–Friday, 8:00 AM–5:00 PM (closed holidays)
Common questions
Do I need a permit if I'm just replacing damaged shingles in one section of my roof (maybe 15% of the roof)?
If the damage is patching (10 or fewer shingles across a small area), it's typically exempt as a repair. However, if you're re-roofing a distinct roof plane or section with multiple new shingles and new underlayment, O'Fallon will likely require a permit. The gray zone is 15–25% of roof area. Call O'Fallon Building Department at (636) 272-1550 and describe the scope: they'll tell you if a permit is needed. When in doubt, pull a permit ($100–$150) rather than risk a stop-work order and fines ($500+).
My contractor said he'd 'handle the permit.' How do I know he actually pulled it?
Ask him for a copy of the permit number and the O'Fallon Building Department approval. You can verify it yourself by calling the Building Department or checking the online permit portal at https://www.ofallon.mo.us/permits using the permit number. Legitimate contractors are happy to share this; if he dodges the question, consider hiring someone else. You are ultimately liable if work is done without a permit, even if the contractor promised to pull it.
I have three layers of shingles. How much more does a tearoff add to the cost?
Tearoff labor for a 2,400 sq ft roof typically costs $1,200–$2,500 depending on complexity (steep pitch, valleys, dormers) and local disposal fees. Disposal of shingle waste runs $200–$600 per dumpster. So plan on $1,500–$2,500 total for tearoff on a medium home. This is mandatory per IRC R907.4 and O'Fallon code; there's no shortcut.
What's the timeline from permit application to final inspection?
Like-for-like asphalt reroofs (single or two-layer existing) typically take 5–7 business days: permit issued same day or next, deck inspection scheduled within 2–3 days, deck passes, underlayment/shingles installed, final inspection within 1–2 days. Material-change projects (asphalt to metal) or three-layer tearoffs add 3–5 days for engineering review or extra labor, so plan 10–14 days total. Weather delays are common in spring/fall.
Do I need ice-and-water shield on every part of my roof, or just the edges?
IRC R905.1.2(a) and O'Fallon code require ice-and-water shield only in the ice-dam zone: 24 inches up from the eaves, or 2 feet inside the warm-wall plane if the attic is unheated. The rest of the roof uses standard synthetic or felt underlayment. This saves cost (ice-and-water shield is pricier) but ensures the vulnerable perimeter is protected. O'Fallon inspectors verify this at final.
What if the roofer finds rot or structural damage in the deck during tearoff?
The project scope expands. The Building Department will see the damage at the deck-nailing inspection and will issue a comment like 'Repair or replace deteriorated sheathing per IRC R802.4 before proceeding.' You'll need a repair estimate (typically $200–$1,500 depending on rot extent), submit it to the City for approval, and the contractor must repair before new shingles go down. This can add 3–7 days and $500–$2,000 to the budget. Plan for this possibility, especially on older homes.
Can I pull the permit myself, or does my contractor have to do it?
You can pull it yourself if you're an owner-occupant and not violating any HOA restrictions. O'Fallon allows owner-builder permits for residential properties. Walk into City Hall with the property address, roof measurements (or a contractor's estimate with square footage), and your ID. The permit application asks for underlayment type, fastening pattern, and existing layer count. If you're unsure about specs, ask the roofer to fill out that section. Most homeowners hire the contractor to pull the permit as part of the job; they're more familiar with the form and follow-up inspections.
My homeowner's insurance said roofing work might not be covered if I do it myself. Should I be concerned?
Yes. Contact your homeowner's insurer before you start and ask explicitly: 'If I hire a licensed roofer, is the new roof covered under the policy?' and 'Will the policy deny a claim if the roofer doesn't have a O'Fallon permit and final inspection?' Most insurers require a licensed contractor and proof of permit/final inspection for coverage. Self-performing roof work is risky liability-wise and may void coverage. Hire a licensed contractor and keep the permit and final-inspection sign-off in your file.
The permit form asks for 'existing shingle layers.' I'm not sure how many are under the current layer. How do I find out?
Your roofer can usually count by pulling up a corner shingle or examining the soffit/gutter edge; they'll see the layers stacked. If you have attic access, you can peek at the underside of the deck—you'll sometimes see nail patterns from previous roofing. If you're really unsure, ask a roofer for a free inspection (most do) before you pull the permit. Declaring the wrong layer count (especially underestimating) can trigger a permit rejection or stop-work order; honesty is essential.
I'm switching to metal roofing. What's the structural engineer letter about?
Metal roofing products vary in weight (0.5–1.5 lbs per sq ft), and some are heavier than standard asphalt (0.4 lbs per sq ft). O'Fallon Building Department wants written confirmation from a structural engineer or the roofing manufacturer that your existing deck framing is adequate for the added load. The engineer reviews the roof plan (span, member size) and compares it to the metal product's dead load. This takes $350–$600 and 5–7 days; without it, the permit won't be approved. Your roofer usually coordinates this or hires the engineer.