Window and siding replacement in Mehlville
What the code and the permit desk actually require here — and what the houses in Mehlville tend to be hiding behind the siding.
- People
- 28,955
- Homes
- 13,854
- Size
- 7.63 square miles
- From downtown
- About 12 miles south
- ZIP codes
- 63125, 63128, 63129
Mehlville is an unincorporated census-designated place -- never a city -- and is 100% urban per census data, encompassing areas also associated with the Lemay, Tesson Ferry, and Oakville townships.
Mehlville
Median home age is about 47 years, consistent with Mehlville's description in census data as a fully urbanized, inner-ring St. Louis County suburb.
What that vintage turns up
Original single-pane aluminium and wood units, most of which have been replaced at least once by now — which means what you are usually looking at is a first-generation replacement window from the 1990s, not the original. Aluminium frames of this age conduct cold straight through and sweat in January, which is what people are describing when they say a room feels draughty in a house with no measurable draught.
Aluminium siding was the default for years and a lot of it is still up. It does not rot and it does not burn; what it does is chalk, so the factory finish oxidises to a powder that comes off on your hand, and it dents and never un-dents. The honest decision on aluminium in decent shape is repaint against replace, and repainting is often the right answer. Later in this window, hardboard and wood-composite lap started going up, and that material has a litigation history rather than a maintenance history.
The one to watch on a house of this age
Plywood and board sheathing under this vintage holds up better than the OSB that came later, which means rot found here is usually local to a flashing failure rather than general. Find the leak, not just the soft spot.
Lead paint. Likely on anything built before 1978, and the rule does not care how much paint there is. 69.2% of the homes in St. Louis 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.
The rules in Mehlville
Siding replacement Conditional
St. Louis County lists re-siding among the “ordinary repairs or minor work for which a building permit will not be required.” The published item reads: “Siding: new or replaced exterior siding (vinyl, metal, wood, hardboard, etc.) including replacing with a different type of siding.” Adding exterior wall insulation under the new siding is exempt too — but insulating the inside face of the same wall is not. The exemption does not reach damage repair: a permit is required to repair a building damaged by termites, fire, wind, flood or earthquake, no matter how small the damage.
Window replacement, same opening Conditional Enlarging or cutting an opening Permit required
Replacing windows inside the existing rough openings is exempt from permit only if the new windows clear three published conditions: they are “the manufacturer’s largest standard size window that will fit within the existing opening” and match the old operating style or give an equal or greater opening area; they have “a maximum U-Factor of 0.34”; and they meet safety glazing where it applies. Glass-only replacement in an existing sash, and storm windows and storm doors, are exempt outright. A permit is required to enlarge or modify a rough opening — and also, unusually, to replace a window with a style that gives a smaller opening area than the one it replaces.
A replacement window here has to be U-0.34 or lower
St. Louis County adopted the 2015 I-codes by Ordinance 27,654, passed 18 December 2019 and effective 1 July 2020 (moved from 1 April 2020 because of Covid). It adopted no standalone energy code: one- and two-family dwellings are permitted to comply through Sections N1101 and N1102 of the International Residential Code instead. The number the County actually enforces on a replacement window is the one written into its own permit-exemption text — U-0.34.
0.34 is the County’s own published figure, taken from the condition it attaches to the window permit exemption rather than from an IECC table.
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 No
St. Louis County licenses mechanical, electrical and plumbing contractors and nothing else. There is no general contractor category and no siding or window category, so a siding or window company can pull a County permit with no County trade licence at all. Individual municipalities may still require their own business licence.
What the permit costs
Valuation-based. The fee comes off the residential table at SLCRO 1100.060, applied to the total estimated cost of work including labour and materials, plus a $47 permit processing fee.
Local quirks
Mehlville is unincorporated, so St. Louis County is its building department and there is no city hall to call. Mehlville is an unincorporated census-designated place in south St. Louis County with no city government, no building department and no municipal code; residential permits are issued by St. Louis County Transportation and Public Works.
Who to call
- St. Louis County
- 314-615-5184 — Mehlville has no building department of its own
- Official
- Director of Transportation and Public Works (Stephanie Leon Streeter, P.E.)
- Permits
- Department page
How Mehlville compares with the rest of St. Louis County
Same county, same climate, same houses. Not the same rules.
| Place | Permit to re-side | Permit for a window | Window must meet |
|---|---|---|---|
| Mehlville | Depends | Depends | U-0.34 |
| Affton | Depends | Depends | U-0.34 |
| Ballwin | Yes | Yes | — |
| Brentwood | Yes | Not published | U-0.28 |
| Chesterfield | Depends | Depends | U-0.34 |
| Clayton | Yes | Yes | U-0.30 |
| Creve Coeur | Not published | No | U-0.35 |
| Des Peres | Yes | Yes | U-0.32 |
| Ellisville | Not published | Not published | — |
| Eureka | Depends | Depends | — |
| Florissant | Depends | Yes | U-0.30 |
| Kirkwood | Not published | Not published | U-0.30 |
| Manchester | Depends | Depends | U-0.34 |
| Maryland Heights | Not published | Yes | U-0.35 |
| Oakville | Depends | Depends | U-0.34 |
| Richmond Heights | Not published | Not published | U-0.28 |
| Town and Country | Depends | No | — |
| Unincorporated St. Louis County | Depends | Depends | U-0.34 |
| University City | Depends | Yes | U-0.32 |
| Webster Groves | Yes | Yes | U-0.35 |
| Wildwood | Depends | Depends | U-0.34 |
Work we have done in Mehlville
Not yet — Mehlville is on our list rather than in our records. We will say so until that changes.
Where these facts came from
Everything on this page about Mehlville was read off a published source. Where a question has no published answer we have said so rather than filling the gap.
Sources: stlouiscountymo.gov · stlouiscountymo.gov · library.municode.com · ecode360.com · ecode360.com
Work coming up in Mehlville?
We will tell you what the rules here are, including when they work in your favour.
Tell us about the house
We answer the phone. If we miss you, we call back.