Attic insulation, air sealing, crawl spaces and walls for homes in Clayton — starting with a free assessment that measures the R-value you actually have. Clayton enforces the 2021 IECC, which sets R-60 for a new attic.
Clayton runs to about 2.5 square miles and roughly 17,380 people. It sits about 8 miles west of downtown St. Louis. Around 6,934 housing units sit inside those boundaries. The community dates back to 1913. We cover ZIP code 63105.
No completed job in Clayton is logged in our records yet, and this page will say so until one is.
The typical home in Clayton dates to around the mid-1950s. Postwar building here often meant three or four inches of fiberglass and no attempt at air sealing. If nobody has touched it since, that is what is still up there.
A mix of pre-1940 construction (about 35% of homes) and mid-20th-century mid-rise/high-rise development.
We work across Clayton rather than one corner of it — Claverach Park, Clayshire, DeMun, Downtown Clayton, The Moorlands, North Clayton, Brentmoor Park, Carrswold, Forest Ridge and Hillcrest included. Construction and vintage change between them, sometimes by thirty years and a whole different framing method, which decides whether a wall can be dense-packed at all.
Settled in 1877 and incorporated in 1913 on land donated by Ralph Clayton, the St. Louis County seat's housing stock ranges from pre-war brick walkups, apartment buildings and mansions to mid-century-modern low- and high-rise towers downtown.
The Census Bureau estimates 6,934 homes in Clayton. 2,433 of them (35%) went up before 1940 — the 5th-highest share of pre-1940 housing among the 44 places on this site. More of today's homes date from before 1940 than from any single decade since, and 71% predate 1980. For St. Louis County as a whole the pre-1940 share is 10%, so Clayton sits above it.
Of 6,222 occupied homes, 63% heat with utility gas and 36% with electricity. Electric heat here is more common than across the county (23%), and ranks 16th of 44 on this site. Which utility program can contribute depends on the heating fuel and on who sends the bill, so that is the first thing an assessment pins down.
55% of occupied homes are owner-occupied and 31% of all homes are single-family detached houses. With houses like these, the conversations we expect most are about wall insulation for walls built empty, a vermiculite check before anything is disturbed and an energy assessment before deciding what to fix first.
| Built | Homes | Share | |
|---|---|---|---|
| Before 1940 | 2,433 | 35% | |
| 1940s | 714 | 10% | |
| 1950s | 837 | 12% | |
| 1960s | 533 | 8% | |
| 1970s | 408 | 6% | |
| 1980s | 233 | 3% | |
| 1990s | 355 | 5% | |
| 2000s | 859 | 12% | |
| 2010s | 515 | 7% | |
| 2020 or later | 47 | 1% |
6,934 homes, Census ACS 2020–2024 (B25034, B25040, B25003); 6,222 occupied.
1,778 of Clayton's 6,934 homes (26%) date from 1950 through 1979. The leaks in houses of that era repeat: nothing over the top plates, wire and pipe holes left open, an unsealed hatch, a bath fan venting into the attic, and in ranches and split-levels, heat lost at the garage ceiling and over cantilevered floors. Sealing the plates, holes and fans comes before any more fiber, and it is usually a day's work, not a renovation.
Clayton enforces the 2021 IECC. Section 500.010 of the Clayton city code adopts the 2021 International Energy Conservation Code as Part VI of its building code, alongside the 2021 International Building, Mechanical, Plumbing, Residential, Fuel Gas, Existing Building and Swimming Pool and Spa Codes, by Ordinance No. 6780, effective November 8, 2022. The Building Division states the 2021 code family took effect January 1, 2023. Section 500.020(F) carries amended violation penalties and stop work order procedures. Electrical work follows the St. Louis County Electrical Code as amended through County Ordinance 24,439, adopted by City Ordinance No. 6131 effective December 14, 2010, and the property maintenance code is the 2015 International Property Maintenance Code.
Under that edition the required attic value for new work here is R-60, and walls R-30, or R-20 cavity plus R-5 continuous, or R-13 cavity plus R-10 continuous, or R-20 continuous. For comparison, the Department of Energy recommends R60 for an uninsulated attic in climate zone 4A, where Clayton sits, and R49 where there are already a few inches up there.
2021 IECC Table R402.1.3, climate zone 4 (except marine), as reproduced in the U.S. Department of Energy / PNNL Building America Solution Center comparison of 2009-2021 IECC and IRC minimum insulation requirements.
Nothing Clayton publishes settles this. Its permit lists name the work types it cares about, and insulation is not among them in either direction. Clayton publishes a short list of work that does not require a permit: painting, carpeting, trim work, installing cabinets where there is no relocation, layout change or electrical work, and flooring. Insulation, air sealing and weatherization appear neither on that list nor on the list of work that requires a permit. So we ask the department directly before the first day on site, and whatever comes back, pulling it is our job rather than yours.
The Building Division requires a Master Plumber licensed through both St. Louis County and the City of Clayton to pull and perform plumbing work, but publishes no general contractor registration requirement and says nothing about insulation contractors.
The published number is 314-290-8463. The department page is here.
Permitting is on us, not on you.
Clayton is on the Missouri side, where most addresses buy their electricity from Ameren Missouri. Its Pay As You Save program publishes $0.20 per square foot on ceiling and attic insulation and $0.06 per square foot on air sealing for the 2026 program year; the incentive comes off the cost and the rest is repaid through a monthly charge on the bill. It counts only when the attic is at R-20 or below beforehand and R-38 or more afterward, when air sealing cuts measured leakage by 20 percent, and when the household has lived there for the past year; for income-eligible households, CommunitySavers can include attic insulation at no charge. Income-qualified households can apply to Community Action Agency of St. Louis County (CAASTLC) (314-863-0015) for free weatherization instead. The full program rules are on the St. Louis County page and in the rebate guide.
Every layer of an insulated attic, explained
Clayton borders City of St. Louis, University City and Ladue. These are the ones we also cover, each with its own energy code and permit rule:
Elsewhere in St. Louis County we also cover:
Missouri sets none of this at state level. Across the 7 places in this table there are 4 different adopted editions (2015 IECC, 2018 IECC, 2021 IECC and 2024 IECC), and 1 of the 7 publishes a permit rule for insulation.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Clayton | 2021 IECC | R-60 | Not published | 314-290-8463 |
| University City | 2018 IECC | R-49 | Not published | — |
| Affton | 2015 IECC | R-49 | Not for an attic top-up | 314-615-5184 |
| Ballwin | Not published | — | Not published | 636-227-2129 |
| Brentwood | 2024 IECC | R-49 | Not published | 314-963-8602 |
| Chesterfield | Not published | — | Not published | 636-537-4000 |
| Creve Coeur | 2015 IECC | R-49 | Not published | 314-872-2500 |
All 21 St. Louis County jurisdictions side by side →
Clayton enforces the 2021 IECC, which sets R-60 for an attic in new work. Whether it reaches a retrofit of an existing house is not published.
Not on paper: Clayton names neither a permit nor an exemption for insulation, so one call to the department at 314-290-8463 settles it first.
Ameren Missouri's Pay As You Save: $0.20 per square foot for an attic starting at R-20 or below and $0.06 per square foot for air sealing in 2026, with the balance on the electric bill. The federal 25C credit ended for work placed in service after December 31, 2025.
The typical home in Clayton dates to around the mid-1950s; the Census Bureau's 2020-2024 median year built is 1954. Of its 6,934 homes, 35% went up before 1940 and 20% in 2000 or later. It is a median for the place, not a survey of individual houses.
Code and permit facts checked September 10, 2026, rebates October 24, 2026; housing: Census ACS 2020–2024. Sources: ecode360.com · claytonmo.gov (2) · onestl.org · basc.pnnl.gov · en.wikipedia.org · censusreporter.org · point2homes.com · ameren.com (2, 3, 4) · energystar.gov · data.census.gov. These change; confirm with the building department at 314-290-8463 or your electric utility first.
Free assessment, measured at the hatch, with the photographs and the number in writing.
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