Extra Bedroom and En-Suite Extensions

What you get

This service suits you if you need another bedroom, or want a main bedroom with its own bathroom, without converting the loft or moving. You get a first-floor layout that connects well to your landing, an en-suite designed for plumbing and ventilation, a useful room downstairs, the approvals your nation needs and the build, managed by us and carried out by vetted teams working under S&K.

It suits you if…

Your family has outgrown a three-bedroom house
You want a main bedroom suite with its own shower room
Your loft is too low or awkward to convert
You want a study, playroom or bigger kitchen on the ground floor as well
You want to add value as well as space

Line drawing: existing house in outline, new work in brick, blue dashed line at first-floor level.

Design points that matter

Connecting to the landing

The new bedroom must be reached from the existing landing, usually through a new opening in the outside wall or by taking part of an existing bedroom as a corridor. We look at the stairs and landing first, because a poor connection can waste much of the new space.

Planning the en-suite

An en-suite needs a route for the soil pipe to the drains, enough fall for waste water and an extract fan to the outside under Part F. Placing it over the ground-floor utility or near an existing drain keeps pipework short and hidden.

Escape window and fire safety

A new first-floor bedroom needs an escape window with a clear opening of at least 0.33 m², at least 450 mm wide and high, and the bottom no more than 1,100 mm above the floor, unless there is a protected route to the stairs. We design the windows to meet this.

Sound and privacy

Bedrooms above a kitchen or family room benefit from an insulated floor to reduce noise. Side-facing upstairs windows usually have to be obscure-glazed, so we place the main bedroom window to the rear and the en-suite window to the side where possible.

Planning and approvals by nation

England

In England, an extra bedroom extension at the rear can be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary. Upper side windows, including en-suite windows, must be obscure-glazed and non-opening below 1.7 m. Side or deeper designs need planning permission, costing £548 (or £575 for applications made from 8 December 2026).

Approval in England: Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.

Building regulations: Building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end.

Wales

In Wales, an extra bedroom at the rear can be permitted development if the first floor goes no more than 3 m beyond the original rear wall and stays 10.5 m from the rear boundary. A two-storey side extension can also qualify if it is 10.5 m from the side boundary, set back 1 m and adds no more than 50% width. Otherwise the fee is £585.

Approval in Wales: Householder planning application: £585. Councils normally decide householder applications within 8 weeks.

Building regulations: Building regulations approval under the Welsh Approved Documents, which differ from England's in places (notably energy efficiency).

Scotland

In Scotland, an extra bedroom on a new first floor makes the extension more than one storey, so Class 1B applies, needing at least 10 m to every boundary. Most plots need a householder application, which costs £371 and is decided within two months. The building warrant then covers the escape window, ventilation and drainage.

Approval in Scotland: Householder planning application: £371. Councils have two months to decide a local planning application.

Building standards: A building warrant from the council's building standards service before work starts, and a completion certificate at the end. Scotland uses its own Technical Handbooks.

Northern Ireland

In Northern Ireland, a rear extra bedroom extension can be permitted development within 3 m of the original rear wall and 7 m from the rear boundary. Upper side windows within 15 m of a neighbouring boundary must be obscure-glazed and non-opening. Other designs need a planning application costing £347, plus building control approval.

Approval in Northern Ireland: Planning application for works to a house: £347. Councils aim to decide local applications within an average of 15 weeks; many take longer.

Building control: Building control approval from the local council under the Building Regulations (Northern Ireland), using the Technical Booklets.

Guide price

As a guide, an extra bedroom and en-suite extension costs £56,000–£75,500 including VAT at 20% for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space), plus about £5,500–£11,000 for the en-suite, based on West Midlands prices and our Standard spec; London and the South East are higher.

Guide prices by region
Region	Per m² of new floor	Typical project
London	£2,400–£3,240 per m²	£67,000–£90,500
South East England	£2,200–£2,970 per m²	£61,500–£83,000
East of England	£2,060–£2,780 per m²	£57,500–£78,000
South West England	£2,060–£2,780 per m²	£57,500–£78,000
West Midlands	£2,000–£2,700 per m²	£56,000–£75,500
East Midlands	£1,960–£2,650 per m²	£55,000–£74,000
North West England	£1,900–£2,560 per m²	£53,000–£72,000
Yorkshire and the Humber	£1,840–£2,480 per m²	£51,500–£69,500
North East England	£1,800–£2,430 per m²	£50,500–£68,000
Wales	£1,840–£2,480 per m²	£51,500–£69,500
Scotland	£1,880–£2,540 per m²	£52,500–£71,000
Northern Ireland	£1,760–£2,380 per m²	£49,500–£66,500

Typical project: a 4 m × 3.5 m footprint on two floors (28 m² of new floor space), plus £5,500–£11,000 for the en-suite. Including VAT at 20%, Standard spec. Essential spec is about 8% less, Premium about 20% more. See all prices and fees or work out your own guide price.

What's included

Free site visit
Measured survey, priced in writing with the design stage
First-floor layout and landing connection
En-suite design with plumbing and extract routes
Permitted development check or planning application
Structural engineering and building regulations approval
The build, carried out by vetted teams working under S&K

How it works

Free site visit
We look at your house, the boundaries, access and drains, and talk through what you need the new space to do.
Design and approval
Measured survey and drawings, then planning permission or a lawful development certificate, depending on the rules where you live.
Engineering and fixed price
Structural calculations and building regulations approval, then a fixed build price in writing.
Build and sign-off
Vetted teams working under S&K build it, and we arrange the completion certificate.

Questions about extra bedroom and en-suite extensions

Does an extra bedroom add value to my house?

It usually does, though not always by the full cost. Nationwide's 2025 research found that adding a double bedroom to a two-bed house was linked to about 13% higher value, and a double bedroom and bathroom on a three-bed, one-bathroom house up to 24%. Local ceiling prices still apply.

How much does an en-suite add to the cost?

We price the en-suite shower room as an extra, at about £5,500–£11,000 including VAT at 20%. That covers the shower, WC, basin, tiling, extract fan and pipework. The cost varies with the fittings you choose and how far the soil pipe has to run to the drains.

How big should a new double bedroom be?

There is no legal minimum size for a bedroom in a house you own, so the test is whether it works. A comfortable double needs room for the bed with space to walk round it, wardrobes and a door that opens freely. We draw furniture on the plans so you can judge the space before anything is built.

Can an en-suite go in a room with no window?

Yes. A shower room without a window is allowed, provided it has a mechanical extract fan to the outside that meets Part F. Many people prefer a window for daylight, but if it faces a neighbour it will usually need obscure glass. We plan the extract route early so the duct is hidden.

What goes on the ground floor below a new bedroom?

Whatever suits you: a bigger kitchen, a family room, a study, a utility or a downstairs shower room. The ground floor usually costs about the same whatever it is used for, apart from kitchen units and bathroom fittings, which are priced separately.

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