Photo: Jaggery · CC BY-SA 2.066% of households live in a terraced house, more than in 99% of UK towns
In Mountain Ash, 55% of residents said they have no religion, beside 47% across Wales’s towns. More adults who have never married than in 92% of UK towns: 41%. This Mid Glamorgan town had 13,002 residents in 5,740 households at the 2021 Census. On the census count, nearly one in ten households live in a detached house.
From 2011 to 2024, 76% of UK towns grew faster than Mountain Ash: +2%
ONS mid-year estimates, each year indexed to mid-2011 = 100. Mountain Ash’s figure is the small areas (2021 LSOAs) that make up the town.
People, mid-2011 = 100
Change by age, 2011 to 2024
About 13,100 people in 2011; 13,400 in 2024.
No year added more people than mid-2022 to mid-2023: 240. Change by age ran from +15% for the 30 to 44 to −5% for the 0 to 15.
A median age of 41.2: Mountain Ash is younger than 74% of UK towns
Share of residents in each five-year age band, Census 2021.
At 12%, residents aged 15 to 24 sit close to the figure across Wales’s towns. Locally, nearly a fifth of residents are 65 or over.
Median age of UK towns of 2,500+
■ Mountain Ash, 41.2. The typical town is 44.4.
Broad ages · share of residents
Women and men · all residents
52% women, 48% men
About 94 men for every 100 women. Across Wales, 51% of residents are women.
6.3% of adults are full-time students, more than in 87% of UK towns
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%.
By class, 20% of adults are in managerial and professional jobs and 34% in routine and semi-routine work (Wales’s towns: 29% and 27%). 7.3% of residents lived at another address a year earlier, a lower share than in 80% of UK towns. Across Wales’s towns, 8% of adults are full-time students.
The Census was taken on 21 March 2021, in term time, so students were counted at their term addresses.
Smaller households than 63% of UK towns: 2.2 people on average
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.
In Mountain Ash, 29% of households have dependent children, beside 27% across Wales’s towns. For Mountain Ash, the census puts shared households of unrelated adults at 1.9%. More one-person households than in 70% of UK towns: 32%.
Mountain Ash sits above 93% of UK towns for households without a car or van (29%)
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
7.3% of households live in a flat or apartment; across Wales’s towns the figure is 14%. Typically, 21% of households have no car or van across Wales’s towns.
Residents born outside the UK: 2.9%, a lower share than 93% 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
By birthplace, the largest groups from abroad were born in EU countries (1.5%) and in the Middle East and Asia (0.6%). Residents born outside the UK: 7.4% across Wales’s towns, for comparison. 99% of residents have English as their main language, a higher share than in 88% of UK towns. Across Wales’s towns, 23% of those born abroad arrived in 2017 or later; here, 16%.
Mountain Ash’s Welsh speakers make up 10% of residents
Welsh language skills, residents aged 3 and over, Census 2021.
Welsh language skills · residents aged 3 and over
The 2021 Census found 1,286 Welsh speakers aged 3 and over, 10% of that age group, against 16% across Welsh towns: fewer than in 68% of them. Within Mid Glamorgan, Pontyclun has the largest share, 20%.
Only 37% of residents describe themselves as Christian in Mountain Ash
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 Mountain Ash · Mid Glamorgan’s towns 95% · Wales’s towns 90%.
Religion · all residents
Beyond White British, the biggest groups are Other White (1.5%), Mixed or multiple (0.8%) and African (0.2%). Typically, 43% of residents describe themselves as Christian across Wales’s towns. Compared with other places, residents who describe themselves as White British are common here: 96%, more than in 92% of UK towns.
In Mountain Ash, 39% of adults are married or in a civil partnership, fewer than in 92% 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
Unpaid carers: 11%, above 93% of UK towns. To put it in context, 43% of adults are married or in a civil partnership across Wales’s towns. The number giving 50 or more hours of unpaid care a week is 597.
21% of adults have a degree-level qualification
Highest qualification, residents 16 and over, Census 2021.
Highest qualification · residents 16 and over
With 21% of its adults qualified to degree level, Mountain Ash compares with 31% across Wales’s towns; another 30% hold no qualification (20%). A levels are as far as 15% have gone so far, many of them students midway to a degree.
87th youngest of 406 UK towns of 9,000 to 18,000 people
Median age, Census 2021. Hover a dot for its students and residents born abroad; click for its page.
Ages run from 25 in Aberystwyth to 60.4 in Sidmouth. Nearest to Mountain Ash in age: Linthwaite and Slaithwaite (41.2), Leicester Forest East and Kirby Muxloe (41.2), Queensbury (41.3) and Pheasey (41.3).
Among its 7 nearest neighbours, 5 are older than Mountain Ash
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 Mountain Ash’s figures, so households in open countryside are left out. The population trend compares with the whole county and nation.
- Estimates since 2021 are modelled. The ONS builds mid-year estimates from the Census, births, deaths and migration records. Mountain Ash’s trend uses the small areas (2021 LSOAs) with most of their people inside it: 13,002 people in 2021, against 13,002 in the built-up area.
- 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 Mountain Ash’s residents
What is the population of Mountain Ash?
The 2021 Census counted 13,002 people in Mountain Ash’s built-up area. The ONS estimates the same small areas held 13,400 people in mid-2024, 2% more than in 2011.
What is the average age in Mountain Ash?
The median age was 41.2 at the 2021 Census, younger than 74% of UK towns. 12% of residents were 15 to 24 and 19% were 65 or over.
How diverse is Mountain Ash?
96% of residents described themselves as White British in 2021, against 90% across Wales’s towns and 95% across Mid Glamorgan’s towns. 2.9% were born outside the UK.
What religion are people in Mountain Ash?
55% said they had no religion and 37% that they were Christian at the 2021 Census; 0.4% were Muslim and 6.6% didn’t answer.
Is Mountain Ash good for families?
29% of households had dependent children in 2021, against 27% across Wales’s towns. Schools are on Mountain Ash’s schools page.
How many people speak Welsh in Mountain Ash?
1,286 residents aged 3 and over, 10%, 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) · ONS mid-year population estimates for 2021 LSOAs, mid-2011 to mid-2024. 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.