How old are the homes in Mountainside Borough, NJ?

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

87.6% (±12.7 points) of the homes in Mountainside Borough, NJ were built before 1980 (2020–2024 American Community Survey).

4.6% were built before 1940.

3.4% were built in 2010 or later.

Figures last updated on November 12, 2026.

Built before 1980: 87.6% (±12.7 points)
Built before 1940: 4.6%
Built 2010 or later: 3.4%

When the homes in Mountainside Borough were built

Housing units by year structure built, 2020–2024
Year built	Mountainside Borough	Union County	New Jersey	United States
2020 or later	0.3% (±0.5 points)	1.0%	1.1%	2.0%
2010 to 2019	3.1% (±2.1 points)	5.8%	6.2%	9.4%
2000 to 2009	4.7% (±2.5 points)	5.9%	9.2%	13.6%
1990 to 1999	0.0% (±1.7 points)	4.0%	8.9%	12.4%
1980 to 1989	4.3% (±3.2 points)	5.0%	11.8%	12.9%
1970 to 1979	0.6% (±1.0 points)	7.9%	12.3%	14.2%
1960 to 1969	25.3% (±6.7 points)	12.5%	12.8%	9.9%
1950 to 1959	46.4% (±8.8 points)	22.0%	13.8%	9.5%
1940 to 1949	10.7% (±5.2 points)	12.3%	6.5%	4.4%
1939 or earlier	4.6% (±3.2 points)	23.5%	17.4%	11.7%

In Mountainside Borough, the share of homes built before 1980 is not measurably different from Union County (78.2%).

It is also higher than in New Jersey (62.8%).

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

In Union County, Mountainside Borough ranks 5 of 21 places with a published estimate, from highest to lowest share of homes built before 1980.

Statewide, it ranks 51 of 564.

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 (87.0%) and the share built before 1980 (87.6%).

Homes built before 1980 in places near Mountainside Borough

Nearest places with a published estimate, compared with Mountainside Borough
Place	Distance	Homes built before 1980	Compared with this place
Mountainside Borough	—	87.6% (±12.7 points)	—
Springfield Township (Union County)	1.8 mi	71.1% (±7.6 points)	Lower
Westfield Town	2.2 mi	79.5% (±6.4 points)	Not measurably different
Summit	2.4 mi	86.2% (±7.4 points)	Not measurably different
New Providence Borough	2.7 mi	75.6% (±7.8 points)	Not measurably different
Garwood Borough	2.8 mi	78.9% (±14.2 points)	Not measurably different
Fanwood Borough	3.0 mi	83.2% (±13.1 points)	Not measurably different
Springfield	3.0 mi	88.7% (±40.0 points)	Not measurably different
Cranford	3.3 mi	70.7% (±19.2 points)	Not measurably different

Nearby places with a measurably lower figure: Springfield Township (Union County), NJ (71.1%).

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

Homes built before 1980 across Union County, place by place

Rank	Place	Homes built before 1980
1	Winfield Township	97.9% (±8.9 points)
2	Hillside Township	91.2% (±7.7 points)
3	Kenilworth Borough	90.0% (±12.8 points)
4	Roselle Park Borough	89.3% (±10.3 points)
5	Mountainside Borough	87.6% (±12.7 points)
6	Cranford Township	86.5% (±6.7 points)
7	Summit	86.2% (±7.4 points)
8	Plainfield	84.7% (±4.7 points)
9	Clark Township	84.1% (±8.9 points)
10	Fanwood Borough	83.2% (±13.1 points)
11	Scotch Plains Township	81.2% (±7.3 points)

Showing 11 of 21 places in Union 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 Mountainside Borough

How old are most homes in Mountainside Borough?

87.6% of homes in Mountainside Borough, NJ were built before 1980 (2020–2024 American Community Survey).

Do homes in Mountainside Borough 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 87.0% and 87.6% of homes in Mountainside Borough were built before then.

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

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 — Mountainside borough, Union County, New Jersey

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 Mountainside borough, Union County, New Jersey (county subdivision:48510, in state:34 county:039).

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.