Adding an ensuite is consistently ranked among the most desired home improvements in the UK. Done well, it adds daily convenience, increases resale appeal, and can meaningfully boost property value — particularly in three- and four-bedroom family homes where the main bathroom is shared between multiple bedrooms.
A basic shower-room ensuite in an existing bedroom typically costs £4,500–£9,000 installed, including all trades, sanitaryware, tiling, and plumbing. A larger ensuite with a bath or high-specification finishes can reach £12,000–£18,000. Budget-driving factors are explored below.
Cost Breakdown
| Item | Typical Cost Range |
|---|---|
| Design and layout planning | £200–£600 |
| Structural work (stud partition, lintel if needed) | £500–£2,500 |
| Plumbing — water supply, waste drainage | £1,200–£3,000 |
| Electrical — fan, lighting, underfloor heating | £600–£1,400 |
| Tiling (floor and walls) | £800–£2,500 |
| Sanitaryware — WC, basin, shower tray or wet-room former | £600–£3,000 |
| Shower enclosure or wet-room glass | £400–£2,000 |
| Vanity unit and mirror | £300–£1,500 |
| Plastering, skimming, painting | £400–£1,000 |
| Fixtures, finishes, accessories | £200–£600 |
| Total (standard shower-room) | £4,500–£9,000 |
| Total (ensuite with bath, high spec) | £10,000–£18,000 |
These are London and South East all-in costs. Expect 10–20% less in the North and Midlands.
Minimum Space Requirements
The smallest practical ensuite is around 1.5 m × 1.8 m (2.7 m²), which can accommodate a WC, small pedestal basin, and compact shower enclosure. A 900 × 900 mm shower tray takes up significantly less space than a 1,200 × 900 mm enclosure — important when you’re working with a sliver of bedroom space.
A wet room (fully waterproofed floor with a drain, no shower tray) can work in even tighter spaces and removes the visual barrier of the tray and screen edge, making a small ensuite feel more spacious.
For a comfortable ensuite with a bath, you typically need at least 3.5–5 m² depending on the bath length (standard 1,700 mm) and the layout of the remaining fixtures.
Where Does the Space Come From?
Most ensuites are created by one of three approaches:
Partitioning off part of a large bedroom. The most common approach. A stud-frame partition is built to divide the room, creating the wet-room zone. The bedroom loses some floor area, so this works best in rooms 14 m² and larger — the remaining bedroom should be at least 9–10 m² to remain practical.
Converting an adjacent large landing cupboard or dressing room. Ideal if the geometry works — existing walls are in place and the location near the soil stack is more likely.
Converting an unused small bedroom. Where one bedroom is very small (under 7 m²), it may be better used as a dedicated ensuite or dressing room. This is particularly effective in properties that are overpowered in bedroom count relative to the bathroom provision.
Plumbing and Drainage
This is the most technically complex element of an ensuite conversion.
Water supply is straightforward — 15 mm hot and cold branches can be run from the existing feed pipes in a cylinder cupboard or airing cupboard, or from the main bathroom if it’s adjacent. Supply pressure may need boosting if the property relies on gravity-fed hot water from a tank in the loft; a shower pump or mains-pressure system upgrade is sometimes required.
Waste drainage is more challenging. The WC must connect to a 110 mm soil pipe with a minimum fall of 1:40. The soil stack is usually on an external or party wall, and the WC should ideally sit within 6 m of it (the practical limit before self-cleaning velocity in the pipe becomes a concern). If the ensuite is too far from the existing stack:
- A macerator pump can handle WC waste and pump it through a 32 mm pipe up to 12 m horizontally or 4 m vertically to the stack.
- A second soil stack can be installed on the external wall below the new ensuite — more expensive (£800–£2,500 for the stack and planning) but more reliable long-term.
Shower and basin waste runs 40 mm pipework at 1:40 to the same stack or to an existing combined waste/drain system.
Building Regulations
An ensuite almost always requires Building Regulations approval. The relevant parts include:
- Part A — if any walls are removed or modified for the partition.
- Part F — ventilation. An internal ensuite with no external window requires mechanical ventilation, typically a 100 mm extractor fan running to an external duct (not into a roof void unless the void itself is ventilated). The fan must run for a minimum overrun period (typically 15 minutes after the light is switched off) and ideally have a humidity sensor.
- Part H — drainage. The local authority or approved inspector will want to confirm fall, connection point, and stack ventilation.
- Part P — electrical installation. Any new circuit (e.g., for underfloor heating or a separate extractor supply) must be designed and certified by a Part P-registered electrician.
- Part L — insulation. Lighting must use efficacious fittings (LED).
Apply via your local authority or use an approved inspector. Many bathroom fitting companies include the Building Regulations application in their package.
Ventilation in Detail
This is the most commonly failed element on ensuite inspections. For an internal ensuite (no window), the ventilation route must reach an external face of the building. Practical options:
- Duct through the adjacent exterior wall — the most reliable and shortest route.
- Duct through the floor into a void and out through a soffit (not into a sealed loft).
- Duct through the ceiling into the loft, then horizontally to a roof tile vent — this is the longest and least preferred route, requiring insulation around the duct in cold loft spaces to prevent condensation.
A 100 mm extractor with a 6 m maximum equivalent duct length (add 1.5 m equivalent for each 90° bend) is the standard minimum.
Layout Tips for Small Ensuites
- Pocket door or barn door — removes the swing clearance of a standard door, saving 0.5–0.8 m² of effective floor space.
- Wall-hung WC — the pan sits off the floor, with a concealed cistern built into the partition wall. Saves 150–200 mm depth versus a close-coupled WC.
- Mirrored cabinet — provides storage without a projecting shelf.
- Wet room — eliminates the tray, visually enlarging the space and making cleaning easier.
- Linear drain — a channel drain along one edge allows the floor to slope to a single line rather than a central point, giving a cleaner aesthetic in a wet room.
Finding a Tradesperson
An ensuite is a multi-trade project: structural (joiner or builder), plumbing, electrical, tiling, and plastering. Options are:
- Main contractor who coordinates subcontractors (easier to manage, mark-up of 10–20% on subcontractors).
- Bathroom specialist who designs and fits, bringing in subcontractors on their terms.
- Self-managed — you hire each trade directly. This requires time and coordination but can save 10–20%.
Always check that the plumber is suitably qualified for hot-and-cold unvented work if your property has a mains-pressure hot-water system, and that the electrician is Part P-registered.
