Adding an ensuite is one of the more popular 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 £10,000–£18,000. The HomeOwners Alliance puts a simple ensuite carved out of a main bedroom at around £5,000 and about 11 days’ work, which sits at the low end of that range.1 Budget-driving factors are explored below.

Cost Breakdown

ItemTypical 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–£3,0002
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

Not every row applies to every job: the low total assumes no structural work and no separate design fee, as when converting an existing cupboard or dressing room, and the high-spec total assumes most rows near the top of their range. The figures lean towards London and the South East; prices are usually lower 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 of about 14 m² or more. As a benchmark, the government’s nationally described space standard for new homes counts a double bedroom as at least 11.5 m² and a single as at least 7.5 m², so a smaller remainder may stop working as a double.3

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 (below the 7.5 m² the space standard sets for a single), 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 (100 mm nominal bore). Approved Document H allows an unventilated WC branch of up to 15 m, laid at a fall of 18–90 mm per metre (roughly 1:55 to 1:11), and a longer run needs venting.4 In practice plumbers aim to keep the WC within about 6 m of the soil stack, which is usually on an external or party wall, and lay the pipe at around 1:40. If the ensuite is too far from the existing stack:

  • A macerator pump can take the WC waste and pump it through small-bore pipe to the stack. Saniflo’s Saniaccess 1, for example, discharges through 22, 28 or 32 mm pipework and pumps up to 5 m vertically or 100 m horizontally.5 Approved Document G accepts a macerator WC only where the home also has a WC that drains by gravity.6
  • A second soil stack can be installed on the external wall below the new ensuite, more expensive (typically £800–£2,500) but more reliable long-term. A new soil and vent pipe is usually permitted development if it rises less than 1 m above the highest part of the roof; on article 2(3) land, such as a conservation area, it cannot go on a wall or roof slope that fronts a highway and forms the principal or a side elevation.7

Basin waste is usually 32 mm and shower waste 40 mm, matching the trap sizes in Approved Document H.4 Lay them to a steady fall to the same stack or to an existing combined waste/drain system: Approved Document H keeps an unventilated basin branch short, at no more than 1.7 m in 30 mm pipe at a fall of 18–22 mm per metre, with longer runs needing a larger pipe.4

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.8
  • Part F, ventilation. A bathroom needs intermittent extract of at least 15 litres per second, and in a room with no openable window the fan must keep running for at least 15 minutes after the room is vacated.9 An internal ensuite therefore needs a fan, typically a 100 mm extractor fan ducted to outside rather than into a roof void, ideally with a humidity sensor.
  • Part H, drainage. The local authority or registered building control approver will want to confirm fall, connection point, and stack ventilation.4
  • Part P, electrical installation. A new circuit (for example for underfloor heating) and any addition or alteration to circuits in the special location around a bath or shower are notifiable: use an electrician registered with a competent person scheme, who can self-certify, or notify building control before work starts.10
  • Part L, energy efficiency, including insulation of any new external wall or ceiling. New fixed light fittings should have lamps of at least 75 light source lumens per circuit-watt, which in practice means LED.11

Apply via your local authority or use a registered building control approver. Many bathroom fitting companies include the Building Regulations application in their package.

Ventilation in Detail

Ventilation is a common sticking point at ensuite inspections. For an internal ensuite (no window), the ventilation route must reach an external face of the building. Practical options:

  1. Duct through the adjacent exterior wall, the most reliable and shortest route.
  2. Duct through the floor into a void and out through a soffit (not into a sealed loft).
  3. 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.

Keep the duct run short with as few bends as possible, and check that the fan’s stated performance at your duct length still delivers the 15 litres per second a bathroom needs.

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%.

If your home has an unvented (mains-pressure) hot-water system and the work affects the cylinder, check that the plumber holds an unvented hot water qualification, and check that the electrician is registered with a competent person scheme.

The rules in this note are those that apply in England. Scotland, Wales and Northern Ireland have their own building standards and permitted development rights.

References (11)

Figures in this note were checked against the sources below on 2 October 2026. Superscript numbers in the text point to them. Every source the site cites, by topic.

  1. 1costfairHomeOwners Alliance, guidance.RN-DX7AANA price, true at 2026-09. Ten improvements with spend against value added, from HomeOwners Alliance research with the Federation of Master Builders and The Guild of Property Professionals. Removing an internal wall for an open plan kitchen diner costs around £3,500 and adds £48,000 in London or £27,000 in Dorset, and most builders finish it in under a week. Garden room £6,700 adds £36,000 in Surrey or £10,000 in London. Kitchen refresh £4,000 adds £15,000. Downstairs loo in an understairs cupboard £1,500 adds £26,000. Ensuite carved from a master bedroom £5,000 adds about £14,525 in London over roughly 11 days. Off street parking £2,000 adds £13,354 on an average Surrey property, with Direct Line putting a parking space at up to 13% of value. Back garden £4,000 adds £9,000. Repainting £1,000 adds £5,000. Loft conversion £20,000 adds £40,000. Obtaining planning permission costs up to £400 and can add up to 10% of value per Hamilton Fraser.
  2. 2costsupplier figureWickes.RN-JA8LUUA price, true at 2026-09. Wickes's published price for the item the cost register files as "bathroom refit, complete, small bathroom", which is the figure a cost footnote on this page points at.
  3. 3technicalvery strongMinistry of Housing, Communities and Local Government, guidance.RN-LFIIEJthe nationally described space standard, which sets the minimum gross internal areas, bedroom sizes, built-in storage and, at paragraph 10(i), the minimum floor to ceiling height of 2.3m over at least 75% of the gross internal area that a local plan may require of new homes
  4. 4technicalvery strongMinistry of Housing, Communities and Local Government.RN-SM6TRWThe statutory source for soakaway design and the discharge hierarchy every garden drainage note should state. Requirement H3(3) lists the order of priority for rainwater discharge: (a) an adequate soakaway or other adequate infiltration system, or where not reasonably practicable (b) a watercourse, or where not reasonably practicable (c) a sewer. Paragraph 3.25 bars infiltration devices within 5 metres of a building or road, in ground where the water table reaches the bottom of the device at any time of year, too close to other drainage fields or soakaways, or where contamination could pollute groundwater. Paragraph 3.26: soakaways serving less than 100 square metres are generally square or circular pits filled with rubble or lined with dry-jointed masonry or perforated ring units. Paragraph 3.27: design to a return period of once in ten years, and for small soakaways serving 25 square metres or less a design rainfall of 10mm in 5 minutes may be assumed as the worst case. Paragraph 3.28 requires percolation tests to derive the infiltration rate, and paragraph 3.30 sends larger soakaways to BS EN 752-4 or BRE Digest 365 Soakaway design. Paragraphs 2.10 to 2.12 cover pervious paving over a granular storage reservoir and warn against its use where sediment or oil spillage would block the pores. For foul drainage, paragraph 2.33 sets a minimum 75mm internal diameter, or 100mm for a WC, and Table 6 gives minimum gradients of 1 in 40 for 75mm and 100mm at peak flows under 1 litre per second.
  5. 5technicalsupplier figureSaniflo, guidance.RN-YLQZ5QSaniflo's product page for the Saniaccess 1 WC macerator, giving its pumping limits (5 m vertical, 100 m horizontal) and its 22, 28 or 32 mm discharge pipework.
  6. 6technicalvery strongMinistry of Housing, Communities and Local Government.RN-YAW64MRequirement G3(4) states the hot water supply to any fixed bath must be designed so the water delivered to that bath cannot exceed 48 degrees C; paragraph 3.65 says this is achieved with an in-line blending valve or other temperature control device with a maximum temperature stop, and 3.66 accepts valves to BS EN 1111:1999 or BS EN 1287:1999 that fail safe. G3(3) requires unvented storage vessels to prevent stored water exceeding 100 degrees C and to convey safety discharge somewhere visible and safe. Regulation 36 and Requirement G2 cap potential consumption in a new dwelling at 125 litres per person per day, or the optional 110 litres per person per day where a planning condition specifies it; G2 applies only to dwellings erected or formed by material change of use. Sections G4 sanitary conveniences, G5 bathrooms and G6 food preparation areas set scale of provision.
  7. 7technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-UW4IU6Class G permits installation, alteration or replacement of a chimney, flue or soil and vent pipe on a dwellinghouse. Not permitted where the chimney, flue or pipe would exceed the highest part of the roof by 1 metre or more. On article 2(3) land (conservation areas, National Parks, AONBs, the Broads and World Heritage Sites) it is not permitted on a wall or roof slope that both fronts a highway and forms the principal or a side elevation. Also excluded where the dwellinghouse was built under Part 20 of Schedule 2.
  8. 8technicalvery strongMinistry of Housing, Communities and Local Government (GOV.UK).RN-Z6AXUWThe full Approved Document A PDF, which carries the deemed-to-satisfy tables a domestic project is checked against. Section 2E covers foundations of plain concrete: paragraph 2E3 gives the recommended minimum widths of strip foundations in Table 10, keyed to ground type and total load of loadbearing walling per linear metre. Table 10 sets, for rock (not inferior to sandstone, limestone or firm chalk, requiring at least a pneumatic or mechanically operated pick to excavate), a width equal to the width of the wall at every load. For medium dense gravel or sand (requires a pick to excavate, a 50mm square wooden peg hard to drive beyond 150mm) and for stiff clay or stiff sandy clay (can be indented slightly by the thumb), the minimum widths are 250mm at 20 kN per linear metre, 300mm at 30, 400mm at 40, 500mm at 50, 600mm at 60 and 650mm at 70. Firm clay and firm sandy clay (thumb makes an impression easily) start at 300mm. The document also covers minimum depth of strip foundations, wall thickness rules for residential buildings up to three storeys (paragraph 2C10 covers internal loadbearing walls in brickwork or blockwork), buttressing, lateral support by floors and at roof level, interruption of lateral support, wall cladding in Section 3, and Section 5 on reducing sensitivity to disproportionate collapse with the building consequence classes.
  9. 9technicalvery strongMinistry of Housing, Communities and Local Government.RN-QD1SFFTable 1.1 sets minimum intermittent extract rates: kitchen with a cooker hood extracting outside 30 l/s, kitchen without one 60 l/s, utility room 30 l/s, bathroom 15 l/s, sanitary accommodation 6 l/s. Extract terminals and fans other than cooker hoods should be as high as practicable and no more than 400mm below the ceiling; a cooker hood should sit between 650mm and 750mm above the hob if the manufacturer gives no figure. Table 1.7 requires background ventilators of at least 8000mm2 equivalent area in habitable rooms and kitchens for a dwelling, 10,000mm2 for a single-storey dwelling. Background ventilators should be at least 1700mm above floor level and at least 500mm from a fan in the same room. On replacement windows, paragraph 3.14 says new windows must carry background ventilators no smaller than the originals, and paragraph 3.15 gives the fallback minimums where the old size is unknown: 8000mm2 habitable rooms, 8000mm2 kitchen, 4000mm2 bathroom. Paragraph 3.32 confirms that replacing an extractor fan or cooker hood on existing cabling is not notifiable.
  10. 10technicalvery strongMinistry of Housing, Communities and Local Government.RN-JYJ3I5The document that decides what electrical work a homeowner may legally do themselves, and the exact list of notifiable jobs. Regulation 12(6A), reproduced at paragraph 2.5, makes only three things notifiable: the installation of a new circuit, the replacement of a consumer unit, and any addition or alteration to existing circuits in a special location. Regulation 12(9) defines special location as, in a room containing a bath or shower, the zone extending vertically from finished floor level to 2.25 metres (or the shower head position if higher) and horizontally 600mm from the edge of the bath tub or shower tray. Paragraph 2.7 states that all other electrical installation work is not notifiable, namely additions and alterations to existing installations outside special locations, and replacements, repairs and maintenance anywhere. Paragraph 2.8 gives worked examples: a built-in cooker is not notifiable unless a new cooker circuit is needed, and connecting an electric gate or garage door to an existing isolator is not notifiable but running a new circuit from the consumer unit to that isolator is. Paragraph 2.2 confirms Part P reaches outdoor work including fixed garden lighting, pond pumps and outbuildings such as sheds, detached garages and domestic greenhouses. Notifiable work must be certified by self-certification by a registered competent person, third-party certification, or a building control body (paragraph 3.1), with the compliance certificate issued within 30 days (paragraph 3.4). Note that Approved Document P is a source of guidance rather than a ban: non-notifiable work still has to comply with BS 7671.
  11. 11technicalvery strongMinistry of Housing, Communities and Local Government.RN-L0FCJXThe in-force U-value tables a DIY insulation or door note must quote, with the exact numbers. Table 4.2, limiting U-values for new fabric elements in existing dwellings, sets roof 0.15, wall 0.18, floor 0.18, swimming pool basin 0.25, window 1.4 or Window Energy Rating Band B minimum, rooflight 2.2, doors with more than 60 per cent of the internal face glazed 1.4 or Doorset Energy Rating Band C minimum, and other doors 1.4 or Doorset Energy Rating Band B minimum. Table 4.3, for existing elements, gives a roof threshold of 0.35 and an improved value of 0.16, which is the figure a loft insulation note needs: paragraph 4.12 says a retained element whose U-value is higher than the column (a) threshold, for example through a loft or garage conversion, should be upgraded to the column (b) value. Paragraph 4.13 allows a lesser upgrade only where the improved value is not technically or functionally feasible or would not achieve a simple payback of 15 years or less. Paragraph 4.8 requires a replacement element to be no worse than the one it replaces as well as meeting Table 4.2. Paragraph 4.10 gives the heritage exception: where character must be maintained, a centre pane U-value of no more than 1.2 or low-emissivity secondary glazing. Note 9 records that the timber window concession of 1.6 or Band C ended on 14 June 2023. The 2021 edition came into force on 15 June 2022; a 2026 edition exists at https://assets.publishing.service.gov.uk/media/69c122a6cfa346b9d4704a55/ADL1_2026.pdf.

  1. How To Add Value To Your Home, HomeOwners Alliance, accessed 2 October 2026. Priced at 2026-09 and left there. hoa.org.uk

  2. Wickes Quadrant Pearlstone Shower Tray 800 x 800mm, Wickes, accessed 2 October 2026. Priced at 2026-09, so no calibration is needed. wickes.co.uk

  3. Technical housing standards: nationally described space standard, Department for Communities and Local Government, accessed 2 October 2026. assets.publishing.service.gov.uk

  4. Approved Document H, Drainage and waste disposal, 2002 edition incorporating 2010 and 2015 amendments, Ministry of Housing, Communities and Local Government, accessed 14 September 2026. assets.publishing.service.gov.uk

  5. Saniaccess 1, Saniflo, accessed 30 September 2026. saniflo.co.uk

  6. Approved Document G, Sanitation, hot water safety and water efficiency, 2015 edition incorporating 2016 and 2024 amendments, Ministry of Housing, Communities and Local Government, accessed 30 September 2026. assets.publishing.service.gov.uk

  7. The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 1, Class G, legislation.gov.uk, accessed 30 September 2026. legislation.gov.uk

  8. Approved Document A, Structure, 2004 edition incorporating 2004, 2010 and 2013 amendments, Ministry of Housing, Communities and Local Government, accessed 14 September 2026. assets.publishing.service.gov.uk

  9. Approved Document F, Ventilation, Volume 1: Dwellings, 2021 edition, Ministry of Housing, Communities and Local Government, accessed 14 September 2026. assets.publishing.service.gov.uk

  10. Approved Document P, Electrical safety: Dwellings, 2013 edition incorporating 2010 and 2013 amendments, Ministry of Housing, Communities and Local Government, accessed 14 September 2026. assets.publishing.service.gov.uk

  11. Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments, Ministry of Housing, Communities and Local Government, accessed 14 September 2026. assets.publishing.service.gov.uk