What actually governs a roof in this metro, what does not, and which of the things contractors tell homeowners are true. Written to be checkable — every claim below names its source.
Missouri has no statewide residential building code. Residential roofing is governed entirely by whatever code a city, village or county has adopted by local ordinance (and by the permit/inspection program that jurisdiction runs). In unincorporated areas the county code applies; in incorporated areas the municipal ordinance applies, and a municipality may also contract permitting back to the county (Wildwood and Manchester both do). Adopted editions across the St. Louis metro range from the 2009 IRC (Creve Coeur) to the 2024 IRC (Brentwood), so the applicable code can change from one side of a street to the other.
Each jurisdiction adopts a model code (almost always an ICC International Residential Code edition) by ordinance, usually with local amendments on file with the building official. There is no state floor and no state pre-emption.
This is the single most important nuance for Metro East roofing: a re-roof is a repair/alteration, not new residential construction, so the statewide Illinois Residential Building Code does NOT itself govern it. Re-roofing in Belleville, Edwardsville, Collinsville, Alton, Granite City, Glen Carbon, Swansea, Fairview Heights, O'Fallon IL, Columbia and Waterloo is governed by each municipality's own adopted code and permit rules — which is why adopted editions in Metro East still range from the 2006 IRC (Swansea, Waterloo) to the 2021 IRC (Edwardsville, Alton, Collinsville).
NEW residential construction only. Per the Capital Development Board: 'The Residential Building Code Act only applies to new residential construction. Residential repairs may be regulated by local Authorities Having Jurisdiction (AHJ).'
Missouri has no state-level roofing contractor license. Licensing and registration are imposed city by city instead, and plenty of metro municipalities require a contractor to be registered with them before pulling a permit — among the cities on this site, Kirkwood, Webster Groves, Ballwin, Brentwood, Wentzville and Lake St. Louis all do, and so does Granite City on the Illinois side. Check the page for your own city.
Illinois licenses roofing contractors statewide under 225 ILCS 335, so any roofer working the Metro East needs a current IDFPR roofing license. Missouri has no equivalent. If a contractor tells you they are “state licensed” in Missouri, ask what they mean — there is no such thing to be.
| Criterion | Figure | What it drives |
|---|---|---|
| Ultimate design wind (Vult) | 115 mph | Fastener schedule and the manufacturer wind rating we specify |
| Nominal design wind (Vasd) | 89 mph (derived, not published locally) | The allowable-stress figure older specs quote |
| Ground snow load | 20 psf | Structure, and how much the eaves hold in a freeze-thaw |
| Frost depth | 30 in | Footings, not roof covering |
| Seismic design category | C residential / D commercial | Lateral bracing and structural connections — not shingles |
Vasd = Vult x sqrt(0.6) = 115 x 0.7746 = 89.1 mph. This is a computed conversion per ASCE 7-16 Section 26.5.1 / IRC Table R301.2.1.3, NOT a figure quoted from a St. Louis jurisdiction's published table. Commonly rounded to 90 mph, which is the legacy 'basic wind speed' the older ASCE 7-05 maps showed for this region.
The code sets minimums; the shingle manufacturer sets the rest. These are the layers, from the frame up.
The metro sits on the northern shoulder of the New Madrid Seismic Zone, which is why this region is assigned seismic design category C for houses and D for most commercial buildings — unusual for the Midwest. St. Louis County even publishes its own wind and seismic bracing guideline for one- and two-family dwellings.
On nailing, the code minimum and the manufacturer requirement are two different things and contractors mix them up constantly. The IRC minimum is four nails per strip shingle. Shingle manufacturers require six to keep a wind warranty in force, and six is what we install — but that is a manufacturer requirement, not a code one. A contractor telling you the code demands six is either mistaken or selling.
Ice barrier requirements are set by the adopted code edition and the local table entry, and most St. Louis metro jurisdictions do not publish their Table R301.2 entry for it.
Missouri and Illinois both sit in the corridor that takes the most damaging hail events in the country, and the St. Louis metro is squarely in it. Across the nine counties on this site, NOAA's Storm Prediction Center logged 504 reports of hail 1 inch or larger from 2016 through 2025, on 97 days, 226 of them in 2025 alone. Each city and county page counts its own. Those are reports from spotters and the public, logged by NOAA's Storm Prediction Center with a location, not a full count, so anyone quoting you a precise “hail events per year” figure for one street is extrapolating.
What matters for your roof is simpler than a statistic: hail damage is often invisible from the ground and obvious from the roof, insurers generally give you a limited window from the date of loss to file, and a bruised mat can look fine for two years and then fail. That is why the inspection is free and photographed.
Each of these pages goes deeper on one job, with the same sources: roof replacement, roof repair, storm damage, roof inspection, roof ventilation, metal roofing, gutters, roof shingles, flat roofing. Every city page adds the permit rule and code edition for that city, plus its own Census housing figures and hail reports.
Free inspection, photographed, and the report is yours either way.
Researched 2026-09-09. Sources: www.stlpr.org · cdb.illinois.gov · cdb.illinois.gov · www.wentzvillemo.gov · www.stpetersmo.net · stlouiscountymo.gov · stlouiscountymo.gov. Rules and staff change; check with the jurisdiction.