How much does an indoor swimming pool cost in the UK in 2026?
8 October 2026 @Hemant
An indoor swimming pool in London and the South East costs from about £84,000 for a garden pool room (pool from £60,000 plus the building from £24,000), from £90,000 for a pool within the house, and from £100,000 for a basement pool. Running costs for a heated 8m × 4m indoor pool used daily are typically £3,300–£6,500 a year.
Those are wide ranges, and that is the honest answer: the pool itself is often the smaller part of the bill. The room around it, the air handling that keeps it dry, and the structural work beneath London homes are what move the price. This guide breaks down every part of the indoor swimming pool cost UK homeowners should budget for, based on the reinforced concrete pools we design and build across London and the South East.
Key takeaways
Pool inside the house: from £90,000
Basement pool: from £100,000, more where underpinning or deep excavation is needed
New pool hall extension or outbuilding: garden pool room from about £84,000; extension from £90,000
Dehumidification system alone: £7,500–£15,000 wall-mounted, £16,000–£36,000 ducted
Running costs: typically £3,300–£6,500 a year for a heated 8m × 4m pool used daily
Planning: many garden pool buildings fall under permitted development; basements, listed buildings and conservation areas usually need consent
Indoor swimming pool prices UK 2026
Where the pool goes decides most of the budget. These are typical all-in figures for a reinforced concrete, tiled pool with heating, filtration, LED lighting and pool hall air handling.
Indoor pool type | Typical cost (2026) | What drives it |
Pool inside the existing house (garage, wing or ground floor conversion) | From £90,000 | Floor structure, ventilation ducting through existing rooms, finishes |
Basement swimming pool, London | From £100,000 | Excavation, underpinning, BS 8102 waterproofing, ducted dehumidification |
New pool hall extension | From £90,000 | Building shell, glazing, insulation, roof, planning |
Garden pool building (outbuilding) | From £84,000 (pool from £60,000 + building from £24,000) | Size, glazing, height limits, services run from the house |
Luxury indoor swimming pool with spa, steam and changing rooms | £250,000+ | Mosaic and stone finishes, wellness areas, automation |
Figures for our own builds match our published pricing (see indoor pool prices). As a reference point, our Opulent Basement Pool in London, with a steam room and changing rooms, was a £300,000 project.
For comparison, an outdoor concrete pool starts from £48,000 and an outdoor liner pool from £36,000. The difference is almost entirely the building and air handling an indoor pool needs.
What drives the cost of an indoor pool: our analysis
The pool shell is the predictable part. On most indoor projects we price, the enclosure and its environment account for more of the budget than the water.
1. The room around the pool. A new pool hall needs foundations, an insulated shell, a roof and usually large areas of glazing. Glazing is where budgets and running costs both climb, because glass loses more heat than an insulated wall and is where condensation forms first.
2. Air handling and dehumidification. An indoor pool evaporates water into the room every hour it is warm. Without proper dehumidification you get condensation, mould and corrosion. A dedicated system costs £7,500–£15,000 installed for a wall-mounted unit and £16,000–£36,000 for a ducted system, which we recommend for any pool used regularly. This is the item buyers most often underestimate, and the one that is most expensive to fix later.
3. Structure in London homes. Basement pools beneath period houses need excavation, underpinning, temporary works and structural engineering. Every basement we build uses BS 8102 waterproofing, because water pressure from the surrounding ground acts on the structure as well as the water inside it.
4. Access. Inner London sites with no machine access mean hand excavation, conveyor spoil removal and craned deliveries. Inner-London projects typically carry a 10–20% premium over Home Counties equivalents.
5. Finishes. Glass mosaic, natural stone and deck-level overflow edges add cost but define a luxury indoor swimming pool. Italian glass mosaic or natural stone typically adds £4,000–£15,000 depending on surface area.
6. Heating source. An air source heat pump costs more to install than a gas boiler or electric heater but is far cheaper to run. For a pool used every day of the year, efficient heating pays back quickly.
The pattern is consistent: the more that is spent on insulation, glazing performance and air handling at build stage, the less the pool costs to run for the next 20 years.
Indoor swimming pool running costs: what to budget each year
For a heated 8m × 4m indoor pool used daily in London, budget around £3,300–£6,500 a year. That covers electricity for the heat pump, filtration, dehumidification and lighting (£2,500–£5,000), pool chemicals (£400–£700) and an annual service (£400–£800).
Cost item (8m × 4m pool, used daily) | Low estimate (per year) | High estimate (per year) |
Electricity (heat pump, filtration, dehumidification, lighting) | £2,500 | £5,000 |
Pool chemicals | £400 | £700 |
Annual service and maintenance | £400 | £800 |
The low end assumes an automatic cover, a variable-speed pump and heat recovery; larger pools, heavily glazed pool halls and higher energy tariffs push costs up. We include a detailed running cost estimate in every indoor pool proposal.
Five ways to keep running costs down
Fit a pool cover. Covering the water when it is not in use cuts evaporation, which reduces both heating and dehumidification load.
Choose a heat pump or heat-recovery air handler. Recovering heat from the extracted pool hall air is the single biggest efficiency gain in indoor pool design.
Invest in the envelope. Insulated walls, roof and high-performance glazing lower heat loss for the life of the building.
Set the air temperature correctly. Keeping the air slightly warmer than the water reduces evaporation (see the ventilation section below).
Use UV or low-chemical treatment. Lower chlorine use improves air quality and reduces chemical spend.
Do you need planning permission for an indoor swimming pool?
Often not for a garden pool building, but usually yes for basements, extensions on sensitive sites, listed buildings and conservation areas.
In England, a swimming pool, or a building or enclosure to house one, can fall under householder permitted development rights (Class E of the General Permitted Development Order 2015), provided it is for a purpose incidental to enjoying the house. London boroughs regularly grant Lawful Development Certificates for garden outbuildings containing swimming pools on this basis, as in this Camden decision for a pool outbuilding.
The main Class E conditions for a pool building:
It cannot sit forward of the principal elevation of the house.
Height is capped at 2.5 metres where the building is within 2 metres of a boundary, which limits enclosed pool halls close to a fence line.
It must be incidental to the house, not separate living accommodation.
Listed buildings, and properties where permitted development rights have been removed by condition or an Article 4 direction, need full planning permission.
Basement pools in London almost always need planning permission, and several boroughs restrict basement development through Article 4 directions or local basement policies. Budget for a structural engineer's report, a construction management plan and party wall agreements.
Building Regulations apply to virtually every indoor pool: structure, drainage, electrical safety, ventilation and energy performance of the pool hall all need sign-off, whether or not planning permission is required. We recommend applying for a Lawful Development Certificate even where permitted development applies; it gives you written proof for when you sell the house.
Ventilation and dehumidification: the part you cannot skimp on
An indoor pool lives or dies by its air handling. Warm water evaporates constantly, and that moisture must be removed before it condenses on glazing, ceilings and inside the building fabric.
The design targets most engineers work to:
Setting | Target | Why |
Relative humidity | 50–60% | Above 60% raises the risk of condensation and mould (Dantherm) |
Air temperature | About 1–2°C above water temperature | Warmer air slows evaporation and keeps swimmers comfortable |
Pool hall pressure | Slightly negative | Stops humid, chlorinated air leaking into the rest of the house |
A proper system combines dehumidification, fresh air supply and heat recovery, and blows warm, dry air across glazing to stop it fogging and dripping. Undersized or domestic-grade dehumidifiers are a common cause of the problems seen in failing indoor pools: peeling paint, rotting window frames and corroded steelwork.
This is also why indoor pool construction should be designed as one system: pool, building fabric, heating and air handling sized together, not bought separately from different trades.
Indoor vs outdoor vs basement pool: which is right for you?
An outdoor pool is the cheapest to build; an indoor pool gives year-round swimming; a basement pool is often the only option on a tight London plot.
Outdoor pool | Indoor pool (house or extension) | Basement pool | |
Typical starting cost | £36,000 (liner) / £48,000 (concrete) | £84,000 (pool room) / £90,000 (in the house) | £100,000 |
Swimming season | About May–September without a cover | All year | All year |
Annual running cost | £1,300–£2,500 (10m × 4m, heated) | £3,300–£6,500 (8m × 4m, used daily) | Similar to indoor; stable ground temperature helps |
Planning | Usually permitted development | Often permitted development for a garden building | Usually full planning permission |
Build time | 8–16 weeks | 4–9 months including the building | 6–12 months |
Best for | Gardens with space and sun | Daily swimmers and wellness use | Urban plots, period homes, privacy |
Outdoor running costs are from our outdoor pool prices guide. Build times for indoor and basement pools depend heavily on the enclosure and structural work, so treat them as typical rather than fixed.
On London sites, the decision is often made by the plot. Where there is no garden space to spare, going down is the way to add a pool, and a well-designed basement swimming pool can include a spa, steam room and plant room within the same footprint.
Indoor pool installation: the build process step by step
A typical indoor pool installation runs from first survey to first swim in four to nine months, with basements at the longer end. Here is how our projects run.
Consultation and site survey. We look at the space, access, ground conditions and how you want to use the pool.
Design and itemised quote. Pool size, depth, finishes, air handling and heating are designed together and priced line by line, so you know exactly what you are paying for.
Planning and approvals. Lawful Development Certificate or planning application, Building Regulations, structural engineering and party wall agreements where needed.
Groundworks and structure. Excavation, foundations or underpinning, then the reinforced concrete pool shell.
Waterproofing. Multi-layer specialist waterproofing; BS 8102 for basements.
Enclosure and services. The pool hall shell, insulation, glazing, plant room, ducting, drainage and electrics.
Tiling and finishes. Mosaic, stone or large-format tiles, coping and surrounds.
Commissioning and handover. Filling, balancing the water, setting the air handling, and a walkthrough of how to run your pool.
Every pool we build carries a 10-year structural guarantee.
Frequently asked questions
How much does it cost to build an indoor swimming pool in the UK?
From about £84,000 for a garden pool room (pool from £60,000 plus the building from £24,000), from £90,000 for a pool within the house, and from £100,000 for a basement pool. A full basement wellness complex with pool, spa, steam room and sauna starts from around £250,000.
How much does an indoor pool cost to run per year?
Typically £3,300–£6,500 a year for a heated 8m × 4m pool used daily, covering electricity, chemicals and an annual service. An automatic cover, heat recovery and a variable-speed pump push you towards the lower end.
Do I need planning permission for an indoor swimming pool?
A garden building housing a pool can often be built under permitted development (Class E), if it meets the height and position rules. Basements, listed buildings, conservation areas and Article 4 areas usually need planning permission. Building Regulations apply in almost every case.
How long does indoor pool installation take?
Usually four to nine months including the building, and six to twelve months for a basement pool. The pool shell itself is quicker; the enclosure, structure and approvals set the timeline.
Is an indoor or outdoor pool better value?
An outdoor pool costs less to build, from £48,000 for concrete. An indoor pool costs more but can be used every day of the year, which for regular swimmers makes the cost per swim far lower.
Does an indoor swimming pool add value to a house?
It can in the right property, particularly larger London and Home Counties homes, where buyers expect wellness facilities. In smaller homes, some buyers see the running costs as a drawback, so treat a pool as a lifestyle investment first.
What size should an indoor pool be?
For lap swimming, 10–12 metres long by 4–5 metres wide works well. If space is tight, a shorter pool with a counter-current swim unit gives you continuous swimming in a smaller footprint.
Can you build a pool in an existing basement?
Sometimes, but most London basement pools are new excavations. An existing basement must be assessed for depth, structure and waterproofing before a pool can be added.
Thinking about an indoor pool? Talk to London's bespoke pool specialists. We'll give you a fully itemised quote at no cost and no obligation: call 0208 058 0871 or send us your project details.
Sources
The Swimming Pool Company: indoor pool prices, outdoor pool prices, Opulent Basement Pool case study
Dantherm: Swimming pool temperature and operating conditions (humidity and air temperature targets)
London Borough of Camden: Lawful Development Certificate for a pool outbuilding, 59 Redington Road (Class E assessment)
Urbanist Architecture: Planning permission for an outdoor swimming pool (permitted development for pools and pool buildings)
Prices are typical 2026 ranges for London and the South East. Every site is different; contact us for an itemised quote.
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