How old are the homes in Cos Cob, CT?

Name: Age of homes in Cos Cob, CT, 2020–2024
Creator: US Census Bureau
License: https://www.census.gov/data/developers/about/terms-of-service.html

71.7% (±11.3 points) of the homes in Cos Cob, CT were built before 1980 (2020–2024 American Community Survey).

28.1% were built before 1940.

9.2% were built in 2010 or later.

Figures last updated on November 12, 2026.

Built before 1980: 71.7% (±11.3 points)
Built before 1940: 28.1%
Built 2010 or later: 9.2%

When the homes in Cos Cob were built

Housing units by year structure built, 2020–2024
Year built	Cos Cob	Western Connecticut Planning Region	Connecticut	United States
2020 or later	0.0% (±1.5 points)	1.0%	0.7%	2.0%
2010 to 2019	9.2% (±4.4 points)	8.2%	4.5%	9.4%
2000 to 2009	2.5% (±1.9 points)	8.9%	7.1%	13.6%
1990 to 1999	6.1% (±4.1 points)	7.1%	7.5%	12.4%
1980 to 1989	10.5% (±5.0 points)	12.3%	12.9%	12.9%
1970 to 1979	13.2% (±5.5 points)	14.1%	13.7%	14.2%
1960 to 1969	7.4% (±3.4 points)	13.7%	13.0%	9.9%
1950 to 1959	19.5% (±6.4 points)	13.4%	14.1%	9.5%
1940 to 1949	3.5% (±2.4 points)	5.1%	6.3%	4.4%
1939 or earlier	28.1% (±6.3 points)	16.3%	20.2%	11.7%

In Cos Cob, the share of homes built before 1980 is not measurably different from Western Connecticut Planning Region (62.6%).

It is not measurably different from Connecticut (67.3%).

It is higher than the national figure (49.7%).

In Western Connecticut Planning Region, Cos Cob ranks 11 of 33 places with a published estimate, from highest to lowest share of homes built before 1980.

Statewide, it ranks 60 of 132.

Rankings use the estimates alone; where margins of error overlap, neighboring ranks may not truly differ.

Why the age of a home matters: lead-based paint

Federal law treats housing built before 1978 as likely to contain lead-based paint.

Before a lease or sale of most pre-1978 housing, the landlord or seller must disclose any known lead-based paint and hazards and give the tenant or buyer the EPA pamphlet (42 U.S.C. § 4852d; 40 CFR part 745, subpart F; 24 CFR part 35, subpart A).

A contractor paid to renovate, repair or paint a pre-1978 home must be a certified firm, use a certified renovator and follow lead-safe work practices under the Renovation, Repair and Painting Rule (40 CFR part 745, subpart E) whenever the job disturbs more than 6 square feet of painted surface in a room or more than 20 square feet outside; window replacement and demolition always count (40 CFR 745.83).

Certification comes from EPA, or from the state where EPA has authorized the state to run the program.

The Census Bureau groups construction by decade, so the share built before 1978 lies between the share built before 1970 (58.5%) and the share built before 1980 (71.7%).

Homes built before 1980 in places near Cos Cob

Nearest places with a published estimate, compared with Cos Cob
Place	Distance	Homes built before 1980	Compared with this place
Cos Cob	—	71.7% (±11.3 points)	—
Riverside	1.3 mi	70.4% (±8.4 points)	Not measurably different
Greenwich (community)	2.3 mi	74.2% (±7.6 points)	Not measurably different
Old Greenwich	2.3 mi	60.9% (±8.6 points)	Not measurably different
Stamford	3.2 mi	58.3% (±2.7 points)	Lower
Glenville	3.9 mi	65.0% (±17.6 points)	Not measurably different
Pemberwick	4.0 mi	77.9% (±18.5 points)	Not measurably different
Byram	4.6 mi	81.4% (±18.5 points)	Not measurably different
Village of Port Chester	5.0 mi	79.7% (±6.3 points)	Not measurably different

Nearby places with a measurably lower figure: Stamford, CT (58.3%).

Distance is measured in a straight line between the Census Bureau’s internal points for each place.

Homes built before 1980 across Western Connecticut Planning Region, place by place

Rank	Place	Homes built before 1980
5	Pemberwick	77.9% (±18.5 points)
6	Coleytown	77.3% (±18.0 points)
7	Old Hill	77.0% (±22.5 points)
8	Noroton Heights	75.6% (±15.6 points)
9	Greenwich (community)	74.2% (±7.6 points)
10	Tokeneke	73.3% (±15.0 points)
11	Cos Cob	71.7% (±11.3 points)
12	New Milford (community)	71.5% (±12.3 points)
13	Inglenook	71.3% (±38.1 points)
14	Riverside	70.4% (±8.4 points)
15	New Canaan (community)	66.9% (±12.2 points)
16	Staples	65.5% (±13.6 points)
17 (tie)	Glenville	65.0% (±17.6 points)

Showing 13 of 33 places in Western Connecticut Planning Region, ranked from highest to lowest.

Cos Cob is a census-designated place: an unincorporated community the Census Bureau draws for statistics, with no municipal government of its own.

It lies inside Greenwich, whose figures include it.

Survey years: 2020–2024 (American Community Survey 5-year estimates).

Margins of error are at the 90% confidence level.

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Questions about Cos Cob

How old are most homes in Cos Cob?

71.7% of homes in Cos Cob, CT were built before 1980 (2020–2024 American Community Survey).

Do homes in Cos Cob need a lead paint disclosure?

A home built before 1978 does, before it is rented or sold, unless an exemption applies (42 U.S.C. § 4852d); between 58.5% and 71.7% of homes in Cos Cob were built before then.

Does a contractor need lead certification to work on older homes in Cos Cob?

Yes, when the job disturbs more than 6 square feet of paint in a room or 20 square feet outside, or replaces a window: the firm must be certified and a certified renovator must direct the work under the Renovation, Repair and Painting Rule (40 CFR part 745, subpart E).

Sources

Selected Housing Characteristics (DP04), 2020–2024 ACS 5-year estimates — Cos Cob CDP, Connecticut

To check these figures in the Census Bureau’s own API, request the variables below from the 2024 ACS 5-year data profile (acs/acs5/profile) for Cos Cob CDP, Connecticut (place:17520, in state:09).

Each estimate (E or PE) has a margin of error beside it (M or PM).

The API needs a free key.

Request a Census API key.

DP04_0017PE, DP04_0017PM, DP04_0018PE, DP04_0018PM, DP04_0019PE, DP04_0019PM, DP04_0020PE, DP04_0020PM, DP04_0021PE, DP04_0021PM, DP04_0022PE, DP04_0022PM, DP04_0023PE, DP04_0023PM, DP04_0024PE, DP04_0024PM, DP04_0025PE, DP04_0025PM, DP04_0026PE, DP04_0026PM

This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.

Figures are published by the US Census Bureau, HUD, the Bureau of Labor Statistics and the FBI; Seayora reproduces them and does not adjust them, except where a sentence says it compares dollar figures after inflation. They describe the whole place, not any one building or street, and are not an appraisal, a rent determination, a tax bill, a safety rating or legal advice.