Window and siding replacement in O'Fallon
What the code and the permit desk actually require here — and what the houses in O'Fallon tend to be hiding behind the siding.
- People
- 94,074
- Homes
- 34,426
- Size
- 30.51 square miles
- From downtown
- About 31 miles northwest
- ZIP codes
- 63366, 63368
- Founded or incorporated
- 1912
First settled in 1856 and incorporated in 1912, O'Fallon's housing is dominated by rapid recent growth; the 1907-era St. Mary's Institute building (National Register, 2007) is a rare pre-20th-century holdover amid the newer subdivisions.
O'Fallon
One of the youngest housing stocks in the metro: median home age is only about 18 years, reflecting explosive growth from 91,316 residents (2020 census) to an estimated 94,074 by 2023.
What that vintage turns up
Builder-grade vinyl, installed new with the house, is now twenty-odd years old and arriving at the low end of its range. The frames usually have life left; the sealed units are the part that goes, and they go quietly — a haze that only shows in certain light, then a permanent film between the panes that will not clean off from either side.
Thin builder-grade vinyl shows a consistent pattern: fade on the elevations that get the sun, brittleness with age, and cracking at the nail slots where it was fastened too tight. Vinyl expands half an inch or more across a twelve-foot length, which is why the installation manual asks for about a dime's thickness of play between the fastener head and the siding. Nailed home, it has nowhere to go and it tears at the slot.
The one to watch on a house of this age
OSB sheathing is what is behind most of these walls, and it fails fast once it gets wet — fast enough that people in the trade call it vertical mulch. A small flashing defect that a 1925 house would have shrugged off because its walls dried out through the air leaks will rot a modern insulated wall instead.
Lead paint. No. The lead rule stops at 1978 and this is comfortably clear of it. 25.0% of the homes in St. Charles County were built before 1980, and on anything pre-1978 the EPA renovation rule applies to both of these trades. Window replacement is never exempt from it, at any size — a single window triggers it. A whole-house re-side clears the twenty square foot exterior threshold on the first wall. What the rule actually requires of a contractor.
Next door
O'Fallon shares a boundary with Lake St. Louis and St. Peters. Where we have a page for a neighbour it is linked; where we do not, the rules there are still different from the rules here.
The rules in O'Fallon
Siding replacement No permit
Expressly exempt. City Code Sec. 500.020 (amendments to the adopted Building Code) lists among work exempt from permit: 'Painting, papering, tiling, carpeting, cabinets, counter tops, tuckpointing, siding, and similar finish work.' The same exemption appears in the amended IRC R105.2 at Sec. 500.330 (residential). Re-siding is therefore explicitly named as exempt work - one of only two jurisdictions in this metro that names siding by word.
Window replacement, same opening No permit Enlarging or cutting an opening Permit required
Sec. 500.020 and the amended IRC R105.2 (Sec. 500.330) exempt 'Replacement of doors and windows where the opening size is not increased or decreased.' The exemption is conditioned on the opening: enlarging an opening, shrinking it, or cutting a new one falls outside the exemption and a permit is required. 'Reroofing of asphalt shingle roofs' is separately exempt.
A replacement window here has to be U-0.30 or lower
City Code Chapter 500, Article IV, Energy Conservation Code: 'That certain document. The IRC's own Chapter 11 energy provisions (N1101-N1104, including a mandatory energy compliance certificate) are also carried in the adopted residential code at Sec. 500.330.
That figure comes from the 2021 edition this jurisdiction has adopted.
A window fitted here must also carry an SHGC of 0.40 or lower.
For comparison, ENERGY STAR asks for U-0.25 or lower with an SHGC of 0.40 or lower everywhere in this metro, which is stricter than every code edition in force here. And the code only bites when the sash and the glazing are replaced together — replace the glass alone in an existing sash, or add a storm window over the top, and it does not apply.
Contractor registration Yes
Chapter 605, Sec. 605.020: 'All merchants doing business within the City of O'Fallon shall be required to purchase and keep on display at their usual place of business a City of O'Fallon business license.' The Finance Department page states plainly: 'The City of O'Fallon requires all businesses to have a valid, unexpired license.' Fee under Sec. 605.030(A)(1)(a) for general merchants: $50 for up to 10,000 sq ft plus $0.03 per additional sq ft, capped at $500 annually. Sec. 605.040(B) requires a Missouri Department of Revenue no-tax-due statement as a prerequisite to issuance or renewal. No bond or insurance requirement and no siding/window/home-improvement trade licence is published in Chapter 605.
Local quirks
The codified adoption is explicit - Sec. 500.010 adopts the International Building Code, 2021 Edition, including Appendix Chapter K, and Sec. 500.330 adopts the International Residential Code, 2021 Edition, with Appendices AE, AF, AG, AH, AI, AJ, AK and AP. O'Fallon also runs unusually generous exemptions relative to its neighbours: detached accessory structures up to 200 sq ft, fences up to 7 feet, and asphalt reroofing all permit-free. Residential contact is Scott Dabney, residential supervisor (sdabney@ofallonmo.gov).
Who to call
- Building dept
- 636-379-5660
- Official
- Nathan Lacey, Building Official (636-379-5597, nlacey@ofallonmo.gov)
- Permits
- Department page
How O'Fallon compares with the rest of St. Charles County
Same county, same climate, same houses. Not the same rules.
| Place | Permit to re-side | Permit for a window | Window must meet |
|---|---|---|---|
| O'Fallon | No | No | U-0.30 |
| Cottleville | Yes | No | U-0.30 |
| Lake St. Louis | Yes | Yes | U-0.35 |
| St. Charles | No | Not published | U-0.35 |
| St. Peters | Yes | Yes | U-0.30 |
| Wentzville | Yes | Yes | U-0.40 |
Work we have done in O'Fallon
We have no finished work in O'Fallon to show you yet. This fills in as jobs land, and not before.
Where these facts came from
Everything on this page about O'Fallon was read off a published source. Where a question has no published answer we have said so rather than filling the gap.
Sources: ofallon.mo.us · ecode360.com · ecode360.com · ecode360.com · ecode360.com · ecode360.com · ofallon.mo.us
Looking at a job in O'Fallon?
We measure egress and safety glazing on the visit, not after the order goes in.
Tell us about the house
We answer the phone. If we miss you, we call back.