Southampton's median flat sold for £160,000 in 2025 — £134,125 short of the city's median house price. That gap, in cash and as a percentage, is wider than the one recorded a few miles along the coast in Portsmouth, where the flat-to-house gap comes to £112,000. The result runs against what the two cities' housing mix would predict: flats make up a bigger slice of Southampton's market (31.6% of 2025 sales) than Portsmouth's (24.3%), yet Southampton's flats and houses sit further apart on price, not closer together.
The 2025 numbers
Medians below are drawn from HM Land Registry Price Paid Data, category A (standard market sales), for the calendar year 2025.
| City | Flat median | House median (detached/semi/terraced) | Cash gap | Gap as % of flat price |
|---|---|---|---|---|
| Southampton | £160,000 (n=868) | £294,125 (n=1,873) | £134,125 | 83.8% |
| Portsmouth | £168,000 (n=605) | £280,000 (n=1,879) | £112,000 | 66.7% |
Southampton's flat median is actually £8,000 cheaper than Portsmouth's, while its house median is £14,125 more expensive. Both effects push the same way: a wider gap.
Why a bigger flat market doesn't mean a smaller gap
The instinct is that a city with more flats on the market would price them closer to houses — more supply, more competition, a flatter price ladder. Southampton's 2025 sales tell a different story:
| Property type | Southampton share | Portsmouth share |
|---|---|---|
| Flat | 31.6% (868) | 24.3% (605) |
| Terraced | 26.5% (727) | 57.2% (1,423) |
| Semi-detached | 27.6% (757) | 14.6% (362) |
| Detached | 14.2% (389) | 3.8% (94) |
Portsmouth's market is dominated by one type — terraced housing accounts for well over half of all sales, a legacy of the city's dense Victorian street plan on Portsea Island. Its house median is therefore mostly a terrace median, and terraces sit closer to flats on price than detached or semi-detached homes do.
Southampton's sales are spread more evenly across all four main types, including a meaningfully larger detached share (14.2% vs 3.8%). Its house median blends in more of the higher-priced detached and semi-detached stock, which pulls the "house" side of the comparison up — even though its flat median is the cheaper of the two cities. The lesson, consistent with findings already published for Portsmouth's island-versus-mainland market, is that a city-wide price gap is usually a composition effect — which house types sell where — rather than a like-for-like location premium.
What it costs each month
Using the Bank of England's latest quoted 75%-loan-to-value five-year fixed rate (4.32%, April 2026) over a 25-year term, plus a twelfth of each city's 2026-27 council tax Band D bill:
| Southampton flat | Southampton house | Portsmouth flat | Portsmouth house | |
|---|---|---|---|---|
| Price | £160,000 | £294,125 | £168,000 | £280,000 |
| Mortgage (75% LTV) | £655/mo | £1,204/mo | £688/mo | £1,146/mo |
| Council tax (1/12 Band D) | £198/mo | £198/mo | £191/mo | £191/mo |
| All-in monthly | £853 | £1,402 | £879 | £1,337 |
Council tax is a flat, city-wide Band D rate in both places — £2,381.48 in Southampton, £2,291.71 in Portsmouth — so it narrows the gap slightly rather than widening it. The monthly flat-to-house difference still comes to £549 in Southampton against £458 in Portsmouth, tracking the same wider-gap pattern as the purchase price.
Try the numbers against your own budget with the mortgage calculator, or look up a Southampton property directly at SO14 0AA.
Stamp duty: no tax due for first-time buyers, either way
All four medians sit below the £300,000 first-time buyer nil-rate ceiling, so a first-time buyer purchasing any of them — flat or house, either city — pays no Stamp Duty Land Tax. A home mover, with no relief, pays more as the price rises through the £125,000 and £250,000 thresholds:
| Price | First-time buyer SDLT | Home-mover SDLT | |
|---|---|---|---|
| Southampton flat | £160,000 | £0 | £700 |
| Southampton house | £294,125 | £0 | £4,706 |
| Portsmouth flat | £168,000 | £0 | £860 |
| Portsmouth house | £280,000 | £0 | £4,000 |
These figures come from HMRC's residential SDLT bands, applied via Homecost's Stamp Duty calculator, and assume a standard residential purchase with no additional-property surcharge. Individual circumstances — joint buyers, second properties, non-UK residence — can change the figure; a conveyancer confirms eligibility on completion.
Energy performance: flats out-rate houses in both cities
Southampton's flats are the greener half of its own market, and greener than Portsmouth's flats too, based on the latest Energy Performance Certificate on record for each address:
| Flats rated C or above | Houses rated C or above | |
|---|---|---|
| Southampton | 58.5% (n=4,525) | 35.0% (n=30,554) |
| Portsmouth | 51.9% (n=3,029) | 30.7% (n=31,398) |
The gap between flats and houses on energy rating mirrors the pattern already logged for Southampton's own city-centre flat market: flats are typically smaller, more recently converted or purpose-built, and cheaper to bring up to modern insulation standards than the UK's older semi-detached and detached housing stock.
The takeaway
A bigger flat market doesn't automatically mean flats and houses price closer together — it depends on what kind of houses fill out the rest of the market. Portsmouth's terrace-dominated stock keeps its flat-to-house gap comparatively narrow; Southampton's more even spread across terraces, semis and detached homes widens it, even with cheaper flats to start from. For the wider picture of how the two cities — and Bournemouth along the coast — compare on the full cost of buying and running a home, see Portsmouth, Southampton and Bournemouth's true cost of buying and running a home, or the standalone average house price in Southampton and average house price in Portsmouth breakdowns. Homecost's true cost of buying a £300,000 home and true cost of buying a £200,000 home guides work through the full cost stack — deposit, stamp duty, mortgage and running costs — at the price bands each city's flats and houses actually sell at. More regional breakdowns are on the Homecost blog.
Figures are drawn from 2,487 Portsmouth and 2,745 Southampton Land Registry sales completed in 2025 (category A, standard market sales), cross-referenced against the EPC register (latest certificate per address) and 2026-27 council tax Band D rates.
This is general information, not financial or tax advice. Speak to a qualified adviser before acting on mortgage or Stamp Duty figures specific to your situation.