Photo: nantcoly · CC BY-SA 2.0A higher share of households in terraced houses than 97% of UK towns, at 47%
Across Wales’s towns, 14% of households live in a flat or apartment; in Treharris, 3.9%. This Mid Glamorgan town had 5,042 residents and 2,184 households at the 2021 Census, with a median age of 44.4 (younger than 51% of UK towns). In Treharris, 13% of residents give unpaid care. More residents who describe themselves as White British than in 92% of UK towns: 96%.
11% of residents are aged 15 to 24, more than in 81% of UK towns
Share of residents in each five-year age band, Census 2021.
Residents aged 65 and over are about as common here as across Wales’s towns: 21%. By way of comparison, 12% of residents are aged 15 to 24 across Wales’s towns. No age band is larger than 55–59: 8.4% of residents. The median age in Treharris is 44.4, lower than in 51% of UK towns.
Median age of UK towns of 2,500+
■ Treharris, 44.4. The typical town is 44.4.
Broad ages · share of residents
Women and men · all residents
51% women, 49% men
About 95 men for every 100 women. Across Wales, 51% of residents are women.
Treharris ranks below 95% of UK towns on residents who moved in within the year: 6.3%
What adults did at the 2021 Census (the ONS’s NS-SEC classes), and where residents lived a year earlier.
Adults by occupation class · residents 16 and over
Address a year before the Census
Residents who lived somewhere else a year earlier. The bar runs to 25%.
With full-time students at 5.4%, Treharris is ahead of 73% of UK towns on that count. Elsewhere, nearly one in ten residents lived at another address a year earlier across Wales’s towns.
The Census was taken on 21 March 2021, in term time, so students were counted at their term addresses.
A smaller share of one-person households than 72% of UK towns: 27%
Household make-up at the 2021 Census. Each square is 1% of households.
Against Mid Glamorgan’s towns and Wales’s towns
People per household
Wales’s towns.
Families with dependent children are 26% of households (Wales’s towns 27%), and 13% are someone 66 or over living alone (Mid Glamorgan’s towns 14%). The share of shared households of unrelated adults stands at 2.1%. Across Wales’s towns, one-person households come to 32%.
Above 55% of UK towns: 16% of households have no car or van
Accommodation type and cars or vans per household, Census 2021. Owning and renting are on Cost of living.
Type of home
Cars or vans · share of households
With households in detached houses at 25%, Treharris is behind 61% of UK towns on that count. One household in every 6 has no car or van.
Residents born outside the UK make up 3% in Treharris, less than in 91% of UK towns
Country of birth, year of arrival and main language, Census 2021.
Born outside the UK, by region · share of all residents; the bar runs to 10%
When those born abroad arrived
Main language · residents aged 3 and over
96% of residents have English as their main language across Wales’s towns, against 99% in Treharris. Against that, 7.4% of residents were born outside the UK across Wales’s towns. Residents born abroad were most often born in EU countries (1.2%), then in the Middle East and Asia (0.9%).
Welsh speakers make up 12% of Treharris
Welsh language skills, residents aged 3 and over, Census 2021.
Welsh language skills · residents aged 3 and over
569 residents, 12% of those aged 3 and over, said they can speak Welsh at the 2021 Census, against 16% across Welsh towns: more than in 50% of Welsh towns. The highest share in Mid Glamorgan belongs to Pontyclun (20%).
Treharris sits above 97% of UK towns for residents with no religion (53%)
How residents described themselves at the 2021 Census. Lines join the lowest and highest of the three figures.
Ethnic groups other than White British · all residents
White British, not charted: 96% of Treharris · Mid Glamorgan’s towns 95% · Wales’s towns 90%.
Religion · all residents
Across Wales’s towns, 43% of residents describe themselves as Christian; in Treharris, 41%. Set beside that, 47% of residents said they have no religion across Wales’s towns. After White British, the most common groups are Other White (1.2%), Mixed or multiple (1%) and Chinese (0.5%).
Adults who have never married make up 34% in Treharris, more than in 60% of UK towns
Legal partnership status (residents 16 and over) and unpaid care (residents 5 and over), Census 2021.
Partnership status · residents 16 and over
Unpaid care given · share of residents 5 and over
Some 202 people give 50 hours or more of unpaid care a week. Typically, 38% of adults have never married or formed a civil partnership across Wales’s towns. Here 48% of adults are married or in a civil partnership, where the figure across Wales’s towns is 43%.
27% of adults have a degree-level qualification
Highest qualification, residents 16 and over, Census 2021.
Highest qualification · residents 16 and over
Degree-level qualifications are held by 27% of adults in Treharris (Wales’s towns: 31%), and no qualification by 23% (Wales’s towns: 20%).
192nd lowest median age among 516 UK towns of 4,000 to 7,000
Median age, Census 2021. Hover a dot for its students and residents born abroad; click for its page.
The youngest is Bailrigg (18.9) and the oldest Barton on Sea (65.3). Nearest to Treharris in age: Cleator Moor (44.4), Shepperton Green (44.4), Bedwas (44.4) and Easington (44.5).
Of the 7 towns nearest Treharris, 3 are older
Nearby built-up areas coloured by median age, Census 2021. Tap a town for its page.
Health, work and homes have their own pages
What this data can and can’t tell you
- The Census was taken in a lockdown, in term time. 21 March 2021 fell in term time, and students were asked to give their term-time address, so most were counted where they study. Some may have been living with family that day.
- “Mid Glamorgan’s towns” and “Wales’s towns” mean their built-up areas. Census comparisons pool every built-up area in Mid Glamorgan (or Wales), summed the same way as Treharris’s figures, so households in open countryside are left out.
- Small counts are blurred. The ONS adds small random changes to Census counts to protect privacy, so the same total differs a little between tables, and the shares of a small town can move by a point or two.
Questions about Treharris’s residents
What is the population of Treharris?
The 2021 Census counted 5,042 people in Treharris’s built-up area.
What is the average age in Treharris?
The median age was 44.4 at the 2021 Census, younger than 51% of UK towns. 11% of residents were 15 to 24 and 21% were 65 or over.
How diverse is Treharris?
96% of residents described themselves as White British in 2021, against 90% across Wales’s towns and 95% across Mid Glamorgan’s towns. 3% were born outside the UK.
What religion are people in Treharris?
53% said they had no religion and 41% that they were Christian at the 2021 Census; 0.4% were Muslim and 4.9% didn’t answer.
Is Treharris good for families?
26% of households had dependent children in 2021, against 27% across Wales’s towns. Schools are on Treharris’s schools page.
How many people speak Welsh in Treharris?
569 residents aged 3 and over, 12%, said they can speak Welsh at the 2021 Census, against 16% across Welsh towns.
Sources: ONS Census 2021, output areas summed to the ONS 2022 built-up area (TS002, TS003, TS004, TS007A, TS008, TS015, TS017, TS019, TS021, TS029, TS030, TS039, TS044, TS045, TS062, TS067, TS032). All under the Open Government Licence v3.0.
Contains public sector information licensed under the Open Government Licence v3.0. Contains HM Land Registry data © Crown copyright and database right 2026. Contains OS data © Crown copyright and database right 2026 (ONS boundaries). Northern Ireland: Source: NISRA; contains Land & Property Services data and Ordnance Survey of Northern Ireland information, © Crown copyright, licensed under the Open Government Licence v3.0. Scotland: contains National Records of Scotland data, Registers of Scotland data and SEPA data, © Crown copyright / © SEPA 2025, licensed under the Open Government Licence v3.0.