How old are the homes in Janesville, WI?

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

62.7% (±3.3 points) of the homes in Janesville, WI were built before 1980 (2020–2024 American Community Survey).

14.2% were built before 1940.

5.1% were built in 2010 or later.

Figures last updated on November 12, 2026.

Built before 1980: 62.7% (±3.3 points)
Built before 1940: 14.2%
Built 2010 or later: 5.1%

When the homes in Janesville were built

Housing units by year structure built, 2020–2024
Year built	Janesville	Rock County	Wisconsin	United States
2020 or later	1.3% (±0.6 points)	1.2%	1.4%	2.0%
2010 to 2019	3.8% (±0.8 points)	4.3%	7.1%	9.4%
2000 to 2009	10.1% (±1.5 points)	10.8%	12.5%	13.6%
1990 to 1999	12.1% (±1.4 points)	10.8%	12.5%	12.4%
1980 to 1989	10.0% (±1.5 points)	8.0%	9.5%	12.9%
1970 to 1979	16.6% (±1.8 points)	14.4%	14.2%	14.2%
1960 to 1969	16.1% (±1.8 points)	13.4%	9.4%	9.9%
1950 to 1959	10.3% (±1.3 points)	10.7%	10.3%	9.5%
1940 to 1949	5.5% (±1.1 points)	7.2%	5.3%	4.4%
1939 or earlier	14.2% (±1.3 points)	19.2%	17.8%	11.7%

In Janesville, the share of homes built before 1980 is not measurably different from Rock County (64.9%).

It is also higher than in Wisconsin (57.0%).

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

In Rock County, Janesville ranks 18 of 28 places with a published estimate, from highest to lowest share of homes built before 1980.

Statewide, it ranks 522 of 1,848.

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 (46.1%) and the share built before 1980 (62.7%).

Homes built before 1980 in places near Janesville

Nearest places with a published estimate, compared with Janesville
Place	Distance	Homes built before 1980	Compared with this place
Janesville	—	62.7% (±3.3 points)	—
Town of Harmony (Rock County)	4.1 mi	46.0% (±11.1 points)	Lower
Town of Janesville	4.3 mi	48.6% (±15.0 points)	Not measurably different
Town of La Prairie	5.2 mi	82.2% (±14.7 points)	Higher
Town of Rock (Rock County)	5.3 mi	66.7% (±19.1 points)	Not measurably different
Milton	7.2 mi	56.9% (±10.4 points)	Not measurably different
Town of Fulton	8.2 mi	40.6% (±12.4 points)	Lower
Town of Milton (Rock County)	8.9 mi	52.7% (±15.7 points)	Not measurably different
Town of Center (Rock County)	9.0 mi	54.6% (±11.2 points)	Not measurably different

Nearby places with a measurably lower figure: Town of Harmony (Rock County), WI (46.0%), Town of Fulton, WI (40.6%).

Nearby places with a measurably higher figure: Town of La Prairie, WI (82.2%).

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

Homes built before 1980 across Rock County, place by place

Rank	Place	Homes built before 1980
12	Town of Beloit	68.4% (±8.9 points)
13	Town of Lima (Rock County)	67.3% (±15.8 points)
14	Town of Rock (Rock County)	66.7% (±19.1 points)
15	Town of Bradford	66.6% (±15.5 points)
16 (tie)	Clinton	63.3% (±11.5 points)
16 (tie)	Edgerton	63.3% (±13.6 points)
18	Janesville	62.7% (±3.3 points)
19	Town of Magnolia	61.5% (±18.4 points)
20	Town of Porter	60.4% (±14.3 points)
21	Milton	56.9% (±10.4 points)
22	Town of Center (Rock County)	54.6% (±11.2 points)
23	Town of Milton (Rock County)	52.7% (±15.7 points)
24	Town of Union (Rock County)	50.3% (±16.8 points)

Showing 13 of 28 places in Rock County, ranked from highest to lowest.

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 Janesville

How old are most homes in Janesville?

62.7% of homes in Janesville, WI were built before 1980 (2020–2024 American Community Survey).

Do homes in Janesville 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 46.1% and 62.7% of homes in Janesville were built before then.

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

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 — Janesville city, Wisconsin

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 Janesville city, Wisconsin (place:37825, in state:55).

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.