Extra bedroom and en-suite extensions in County Down

County Down at a glance

Nation: Northern Ireland
Price region: Northern Ireland
Postcode areas: BT
Towns covered: 15 listed below, plus surrounding villages
Approval route: It may be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary.
Site visits: Free, no obligation

What an extra bedroom and en-suite extension involves

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.

County Down towns we list: Bangor (County Down) (BT19), Newtownards (BT22), Newry (BT35), Banbridge (BT32), Dundonald (BT16) and Holywood (BT18). Every other address in County Down is covered as well.

Guide price in Northern Ireland

Expect an extra bedroom and en-suite extension in County Down to land somewhere around £49,500–£66,500 (plus £5,500–£11,000 for the en-suite) for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). Our Northern Ireland guide rate is £1,760–£2,380 per m², including VAT. Kitchens, bathroom fittings and flooring are priced separately so you can compare like with like.

Spec	Per m²	Typical project
Essential	£1,620–£2,190 per m²	£45,500–£61,000
Standard	£1,760–£2,380 per m²	£49,500–£66,500
Premium	£2,110–£2,850 per m²	£59,000–£80,000

Rules in 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.

There is no Party Wall Act in Northern Ireland. Shared walls and boundaries are a matter of title and common law, so we agree access and record conditions with neighbours before work starts.

Getting the design right

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.

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.

How we work in County Down

Start at your house
We come to your home in County Down, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
Drawings and permission
Our designers produce plans and elevations, then we take care of planning or permitted development checks with the council covering County Down.
Technical design
We prepare the building regulations drawings, structural calculations and specification so the build price can be fixed.
Build
Foundations, walls, floor, roof, windows, then first and second fix. We break through into the house as late as we can.

Towns we cover in County Down

Extra bedroom and en-suite extensions in County Down: questions

How much does an extra bedroom and en-suite extension cost in County Down?

In Northern Ireland our guide is £1,760–£2,380 per m² including VAT, so about £49,500–£66,500 (plus £5,500–£11,000 for the en-suite) for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). Essential and Premium specs move that by roughly 8% down or 20% up.

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.

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.

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.

Will I need planning permission in County Down?

County Down is in Northern Ireland. It may be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary.

Neighbouring areas

All extension services in County Down · About extra bedroom and en-suite extensions