If you are planning a roof project this year, you might think the only thing you need to worry about is picking a shingle color. But in 2026, the City of O’Fallon has some pretty strict rules you have to follow. These aren’t just “red tape”—they are designed to make sure your house stays dry during those crazy Missouri ice storms and summer downpours.
As a residential roofers ofallon mo, we have to know these codes inside and out to pass our inspections. Here is the 2026 breakdown of what the city expects from your new roof.
1. The Code: 2021 International Residential Code (IRC)
As of January 1, 2026, the City of O’Fallon is officially enforcing the 2021 International Residential Code (IRC). This is a set of global standards, but the city adds its own “local flavor” to deal with our specific weather.
Key Code Rules for 2026:
- Fasteners: Every shingle must be nailed downnot stapled according to the manufacturer’s instructions. Nails have to penetrate the roof deck by at least 3/4 of an inch to make sure they don’t pop out during high winds.
- Drip Edges: You are now required to have a drip edge at both the eaves (the bottom) and the rakes (the sides) of your roof. This keeps water from sneaking behind your siding and rotting your house’s frame.
- Flashing: If your roof touches a wall (like where a garage meets the house), we have to use “step flashing”. You can’t just slap a bunch of tar on it and call it a day.
2. The Ice Barrier Rule: Protecting Your Ceilings
O’Fallon is famous for ice storms that can cause “ice damming.” This happens when snow melts, runs down to the cold edge of your roof, and freezes again, creating a dam that forces water under your shingles.
The 2026 Requirement:
The code mandates a self-adhering “Ice and Water Shield” that must extend from the lowest roof edge to a point at least 24 inches inside the exterior wall line. If your roof is really steep, this barrier has to go even higher—at least 36 inches from the edge.
Wondering if a metal roof handles ice better than shingles? Check out our Metal vs Shingle Comparison for the facts.
3. The Tear-Off Rule: No More Layering
In the old days, people would just put new shingles over old ones to save money. In 2026, O’Fallon has put a stop to most of that.
You MUST tear off the old roof if:
- There is already a single layer and the roof deck underneath is rotted or water-soaked.
- There are already two layers of roofing material.
- The existing shingles are badly curled or warped.
Tearing off an old roof adds to the labor cost. You can see the price breakdown in our 2026 O’Fallon Roof Cost Guide.
4. Ventilation: Letting Your House Breathe
A lot of people think their attic should be sealed tight, but it actually needs to breathe. The code requires 1 square foot of ventilation for every 150 square feet of attic space.
Without proper vents, your attic gets too hot in the summer (raising your Ameren bill) and too moist in the winter (causing mold and ice dams). If we do a re-roof, we are not allowed to block or reduce your existing vents.
5. Permits and Inspections
Yes, you need a permit to replace your roof in O’Fallon.
- The Cost: Permit fees in O’Fallon are based on a multiplier of your construction cost, but there are minimum fees starting at around $25 to $150 depending on the project.
- The Inspection: Once we are done, a city inspector will often come by to make sure we did everything right. They check the shingles, the flashing, and the ventilation to make sure your house is safe.
Why You Need a Pro Who Knows the Rules
If you hire a “tailgate roofer” who doesn’t pull a permit, you might save a few bucks now, but it will haunt you later. When you go to sell your house, a home inspector will see the missing drip edges or the lack of ice shield, and you’ll have to pay to fix it all over again.
At Prrotect Roofing, we handle all the permits and make sure every nail is where the code says it should be. We don’t cut corners because we want your roof to last for the next 30 years—not just until the next storm.
Contact Prrotect Roofing today. We’ll make sure your roof project is 100% code-compliant and built to last.
