Looking for a spray foam installer in St. John, MO? Describe your project once and up to three spray foam installers who work in St. John and St. Louis County get back to you with a quote. It's free and there is no obligation.
St. John is home to about 6,472 people (2024 Census Bureau estimate), a shrinking community (−2.5% since 2020). With 4,545 people per sq mi, it is a densely built-up area. Hot summers, cold winters and leaky older homes make air sealing a priority here.
St. John at a glance
- Population (Census Bureau estimate, 2024)
- 6,472 (−2.5% since 2020)
- Rank in Missouri
- 112th of 938 cities and towns
- Land area
- 1.4 sq mi
- Population density
- 4,545 people per sq mi (densely built-up)
- Type
- City (St. John city)
- Main county
- St. Louis County
What to check before hiring in St. John
- Training: ask about applicator training and safety practices.
- Code: in Missouri, the energy and residential codes set R-values and barrier requirements.
- Rebates: utilities sometimes rebate insulation upgrades.
- Price drivers: area, foam type, thickness and prep.
Useful official resources
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U.S. Department of Energy: insulation
Official information and guidance.
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Spray Polyurethane Foam Alliance
Official information and guidance.
Services available in St. John
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Attic spray foam
Spray foam on the roof deck or attic floor, often to create a conditioned attic.
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Walls, rim joists and crawl spaces
Spray foam in open walls, rim joists, basements or crawl spaces.
Frequently asked questions in St. John
How much does spray foam cost in St. John, MO?
It depends on area, foam type and thickness. Describe your project: installers who serve St. John reply with a quote.
How long does installation take?
Often a day for a typical attic, plus curing time.
Can foam go over old insulation?
Usually old material is removed first; ask the installer.
Which spray foam installers will contact me?
Up to three independent spray foam installers who serve St. John and the surrounding area, chosen for the service you need. Your details are shared only with your consent.
Source: U.S. Census Bureau, Population Estimates Program (Vintage 2024) and Gazetteer Files (public domain), imported on 10/31/2026. Figures describe the incorporated place or county as published; they are shown for information only.