How old are the homes in Diamond Bar, CA?

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

49.6% (±3.5 points) of the homes in Diamond Bar, CA were built before 1980 (2020–2024 American Community Survey).

0.6% were built before 1940.

1.5% were built in 2010 or later.

Figures last updated on November 12, 2026.

Built before 1980: 49.6% (±3.5 points)
Built before 1940: 0.6%
Built 2010 or later: 1.5%

When the homes in Diamond Bar were built

Housing units by year structure built, 2020–2024
Year built	Diamond Bar	Los Angeles County	California	United States
2020 or later	0.1% (±0.1 points)	0.9%	1.3%	2.0%
2010 to 2019	1.4% (±0.6 points)	4.8%	6.5%	9.4%
2000 to 2009	3.0% (±0.9 points)	5.8%	11.2%	13.6%
1990 to 1999	4.1% (±1.0 points)	6.1%	10.1%	12.4%
1980 to 1989	41.7% (±2.8 points)	12.0%	14.9%	12.9%
1970 to 1979	28.5% (±2.9 points)	13.8%	16.8%	14.2%
1960 to 1969	17.2% (±1.8 points)	14.0%	12.5%	9.9%
1950 to 1959	2.8% (±0.8 points)	18.8%	12.4%	9.5%
1940 to 1949	0.5% (±0.3 points)	9.5%	5.4%	4.4%
1939 or earlier	0.6% (±0.4 points)	14.3%	8.9%	11.7%

In Diamond Bar, the share of homes built before 1980 is lower than in Los Angeles County (70.4%).

It is also lower than in California (56.0%).

It is not measurably different from the national figure (49.7%).

In Los Angeles County, Diamond Bar ranks 120 of 140 places with a published estimate, from highest to lowest share of homes built before 1980.

Statewide, it ranks 641 of 1,076.

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 (21.1%) and the share built before 1980 (49.6%).

Homes built before 1980 in places near Diamond Bar

Nearest places with a published estimate, compared with Diamond Bar
Place	Distance	Homes built before 1980	Compared with this place
Diamond Bar	—	49.6% (±3.5 points)	—
Walnut	3.3 mi	38.5% (±3.6 points)	Lower
Rowland Heights	4.7 mi	62.3% (±4.3 points)	Higher
South San Jose Hills	5.0 mi	82.0% (±8.3 points)	Higher
Pomona	5.1 mi	65.6% (±2.7 points)	Higher
Brea	5.9 mi	54.6% (±4.4 points)	Not measurably different
West Covina	6.5 mi	76.6% (±2.7 points)	Higher
Chino Hills	6.6 mi	17.1% (±2.1 points)	Lower
Valinda	7.0 mi	89.0% (±6.6 points)	Higher

Nearby places with a measurably lower figure: Walnut, CA (38.5%), Chino Hills, CA (17.1%).

Nearby places with a measurably higher figure: Rowland Heights, CA (62.3%), South San Jose Hills, CA (82.0%), Pomona, CA (65.6%).

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

Homes built before 1980 across Los Angeles County, place by place

Rank	Place	Homes built before 1980
114	Bradbury	60.3% (±13.7 points)
115	Malibu	59.9% (±7.6 points)
116	Quartz Hill	59.8% (±10.1 points)
117	Manhattan Beach	59.2% (±4.3 points)
118	Agoura Hills	53.3% (±5.7 points)
119	Rose Hills	52.5% (±14.5 points)
120	Diamond Bar	49.6% (±3.5 points)
121	Signal Hill	48.9% (±8.8 points)
122	Marina del Rey	46.4% (±10.9 points)
123	Agua Dulce	44.1% (±13.9 points)
124	Irwindale	42.0% (±11.8 points)
125	Sun Village	38.8% (±11.2 points)
126	Walnut	38.5% (±3.6 points)

Showing 13 of 140 places in Los Angeles 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 Diamond Bar

How old are most homes in Diamond Bar?

49.6% of homes in Diamond Bar, CA were built before 1980 (2020–2024 American Community Survey).

Do homes in Diamond Bar 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 21.1% and 49.6% of homes in Diamond Bar were built before then.

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

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 — Diamond Bar city, California

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 Diamond Bar city, California (place:19192, in state:06).

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.