Window and siding replacement in Wentzville
What the code and the permit desk actually require here — and what the houses in Wentzville tend to be hiding behind the siding.
- People
- 48,646
- Homes
- 15,316
- Size
- 20.94 square miles
- From downtown
- About 35 miles west
- ZIP codes
- 63385
- Founded or incorporated
- 1855
A 'Historic Downtown Wentzville' commercial area exists (subject of a Missouri State Parks reconnaissance survey) and the individually NRHP-listed Wentzville Tobacco Company Factory sits there, but no officially named local or NRHP historic district covering the town was confirmed in this research.
Wentzville
Median house/condo built is 2007; Wentzville was Missouri's fastest-growing city by percentage from 2000-2020, expanding from 7,058 to 44,372 residents, so the large majority of its housing stock is 21st-century new construction.
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.
Neighbourhoods
We work across Bear Creek.
The rules in Wentzville
Siding replacement Permit required
Wentzville rewrote the residential exempt-work list down to three items — detached accessory structures under 120 square feet, a line making all fences permit-worthy, and flatwork other than driveways. Siding is not among them.
Window replacement, same opening Permit required Enlarging or cutting an opening Permit required
Neither the residential nor the commercial exempt list as Wentzville amended it exempts window replacement.
A replacement window here has to be U-0.40 or lower
Wentzville adopted the 2021 IRC in January 2024 and adopted no separate IECC. What makes this page worth reading is that the city wrote its own version of Table N1102.1.3 into the ordinance, and for Climate Zone 4 it sets the fenestration U-factor at 0.40 with SHGC “NR” — not required. That is looser than the model 2021 code and looser than every other jurisdiction in this metro that has a number at all.
0.40 is Wentzville’s own figure, written into its adopted energy table rather than taken from the model code.
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
Building Permits page: 'All contractors, generals and subs, are required to have a City issued contractors license prior to performing work in the City, this is required to be renewed every year by February 28.' This is a blanket requirement with no trade carve-out, so a siding or window contractor is covered. Application is via a CognitoForms 'Contractor License Application' linked from the city site; the Building Fees page notes contractor licensing is handled by the City Clerk's office rather than the Building Division. No fee, bond or insurance amount is published.
What the permit costs
Calculated from the ICC estimated construction cost table with a 0.0050 multiplier applied.
Local quirks
Construction hours are restricted to 6 a.m.-9 p.m.
Who to call
- Building dept
- 636-327-5101
- Official
- Not published. Any site printing a name here is guessing.
- Permits
- Department page
How Wentzville 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 |
|---|---|---|---|
| Wentzville | Yes | Yes | U-0.40 |
| Cottleville | Yes | No | U-0.30 |
| Lake St. Louis | Yes | Yes | U-0.35 |
| O'Fallon | No | No | U-0.30 |
| St. Charles | No | Not published | U-0.35 |
| St. Peters | Yes | Yes | U-0.30 |
Work we have done in Wentzville
No completed job in Wentzville on the books. Every other page on this site is sourced, so this one stays honest too.
Where these facts came from
Everything on this page about Wentzville was read off a published source. Where a question has no published answer we have said so rather than filling the gap.
Sources: library.municode.com · wentzvillemo.gov · wentzvillemo.gov · wentzvillemo.gov · wentzvillemo.gov · wentzvillemo.gov · wentzvillemo.gov
Thinking about it in Wentzville?
A measurement and a written scope costs you nothing and takes about an hour.
Tell us about the house
We answer the phone. If we miss you, we call back.