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Illustrative AI-generated visualisation. Not an actual installation.
What if the swimming pool you’ve always wanted was hiding beneath your garden?
Look closely at the lawn. That strip of glass is the only clue.
Illustrative AI-generated visualisation. Not an actual installation.
Daylight from the garden above, falling onto the water.
AI-generated illustration
It is ambitious, expensive and architecturally complex. But pools like this have been built beneath gardens, with the lawn put back on top. Here’s what it would really take.
From the garden you see a strip of glass. The pool room beneath it is far larger: it runs on under the lawn, with soil, a structural roof and the garden itself on top.
The rooflight is only a window. The pool room runs on beneath the lawn.
A simplified illustration drawn by PlotNua, not to scale and not an engineering drawing. Every real project is designed for its own site.
An underground pool is a basement project first and a swimming pool second. In outline, a project like this would usually go through five stages.
Midway through: the box goes in, then the garden goes back on top.
AI-generated illustration
An illustration of the idea, not an engineering drawing or a construction method. Every real project is designed by its own architect and engineer for its own site.
Ground conditions, groundwater, drainage, access for machinery and the neighbouring buildings are investigated before anything is drawn.
Planning permission and the building control process come before any digging (see below).
The walls that hold back the ground are usually formed first, and the soil inside them is then dug out. At one London project the excavation was made inside a wall of concrete piles cast in 16-metre holes.
A waterproofed concrete box is built: floor, walls, the pool tank and a structural roof strong enough to carry soil and garden.
Soil goes back over the roof, the lawn and planting are reinstated, and only the rooflight and a discreet vent remain visible.
Most of the difficulty is invisible once it’s finished. These are the questions a design team would work through first.
Digging several metres down beside boundary walls and neighbouring houses needs engineered retaining walls and a careful plan for keeping the excavation stable while the work goes on.
A room below ground sits in the groundwater. The design has to keep water out, and to understand how groundwater moves around the new structure so that neighbouring properties aren’t affected.
The chamber needs a complete waterproofing strategy, and rainwater landing on the rooflight and the garden above needs somewhere to go. Pumps and sumps are common below ground.
A heated indoor pool fills a room with warm, humid air. Mechanical ventilation and dehumidification are essential, not optional, and the plant needs its own space and an air path to the outside.
Radon is a natural radioactive gas from the ground. Building regulations in Ireland include radon provisions for new buildings, and a room below ground deserves particular attention in the design.
The room needs a safe way in and out, and a pool needs constant supervision of children. Lockable doors and pool covers reduce risk; they don’t replace supervision.
An indoor pool runs every day: water treatment, filtration, heating and the air-handling plant all need routine servicing, and the waterproofing and drainage need checking over the life of the building.
Excavation means machinery, lorries removing soil and months of work in the garden. Access, where the soil goes, noise and the neighbours all shape the plan.
An underground swimming pool should be treated as a project likely to require planning permission.
The planning exemptions for house extensions and for sheds and similar garden structures do not mention excavated swimming pools, so they should not be assumed to apply. Speak to your local planning authority early. A Section 5 declaration can give a formal answer on whether specific works are exempt.
An underground pool room connected to a house is likely to be treated as an extension. Since 27 July 2026, extensions to a dwelling over 45 square metres come within the building control commencement and certification process, so ask your architect how it applies to your project.
Planning decisions turn on the site. In 2025, permission for a basement-level pool-house extension in Howth, Co. Dublin, was refused on appeal; the reasons concerned the visual impact in a protected landscape area and a separate enforcement matter, not the idea of building below ground.
We haven’t found published Irish prices for an underground pool.
It combines a basement build, a swimming pool and a climate-controlled room, so it is one of the most substantial projects a homeowner can undertake. Costs depend heavily on ground conditions, access, size and finish. An architect and a structural engineer can tell you what your garden would involve before anything is designed in detail.
Private pools below ground exist in Irish homes. Pools built beneath a garden and covered over again are rarer: the clearest published examples are in London.
Carmody Groarke renovated a 19th-century mansion and added a network of underground rooms and a subterranean spa beneath the family home. Its 17-metre pool is lined in black basaltina stone.
Architect: Carmody Groarke
Explore this project (opens the architect’s project page in a new tab)A new seven-bedroom Victorian-style house in a conservation area includes a basement leisure suite with a swimming pool, Jacuzzi, gym and steam room.
Initial design concept: the late Sam Stephenson · Planning design and project management: Nicholas Sweeney Architects
Explore this project (opens the architect’s project page in a new tab)A moving-floor swimming pool was inserted beneath the rear garden of a Grade II* listed house, and the garden was reinstated in a simple formal style. Rooflights and a curved lightwell bring daylight below, and the floor can rise so the room doubles as a games room or cinema.
Architect: Haines Phillips Architects
Explore this project (opens the architect’s project page in a new tab)A 20-metre pool and a gym sit in a new basement now entirely covered by the garden, built inside a wall of concrete piles cast in 16-metre holes. Rooflights in the gym double as sections of glass floor in the garden above.
Architect: Dyer Grimes Architects
Explore this project (opens the architect’s project page in a new tab)Projects are described from the architects’ own published project pages and other published sources, checked on 1 November 2026. No project photographs are shown. Inclusion doesn’t mean a firm currently offers this work in Ireland, or that it has any arrangement with PlotNua. PlotNua doesn’t recommend or endorse any provider.
Last checked 1 November 2026. PlotNua is an independent discovery platform and does not recommend or endorse any provider mentioned. The images of the garden and the pool on this page are AI-generated illustrations, not photographs of an actual installation; the section drawing is a simplified PlotNua illustration.
The homeowner decision
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Explore underground pool possibilities: how one is built, why it isn’t for every garden, planning, cost and real projects.
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PlotNua doesn’t design or build pools and can’t confirm planning permission or whether a property is suitable; that needs an architect and a structural engineer. Nothing is booked by starting a conversation.
The first question is whether your ground, your boundaries and your budget could support a structure like this at all.
A residential architect can tell you whether the idea suits your site, and lead the design and the planning application.
A chartered structural engineer looks at the ground, groundwater and neighbouring buildings, and at how the excavation could be held up.
Then the specialists: a contractor experienced in basements, waterproofing, and a pool and ventilation designer, usually brought in by the design team.
These are professional directories, provided for information. Listing doesn’t mean a member designs or builds underground pools, and PlotNua has no arrangement with these organisations.
