Extra bedroom and en-suite extensions in Dundonald
We cover Dundonald and the rest of County Down for extra bedroom and en-suite extensions. Start with a free site visit and a plain-English view of what your house and plot can take.
Before you start in Dundonald, here's what applies.
- Postcode districts
- BT16
- County / area
- County Down, Northern Ireland
- Price region
- Northern Ireland
- Guide price
- £49,500–£66,500 (£1,760–£2,380 per m²), plus £5,500–£11,000 for the en-suite
- 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.
- Nearest towns
- Holywood (3.4 miles), Comber (3.7 miles), Castlereagh (3.7 miles)
- Distance to Bangor (County Down)
- about 7 miles
- First visit
- Free, no obligation
About an extra bedroom and en-suite extension
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.
Around Dundonald we also work in Holywood, Comber and Castlereagh, and across the rest of County Down. Postcode district in and near Dundonald: BT16.
What it costs in Dundonald
In Northern Ireland, which includes Dundonald, we'd expect an extra bedroom and en-suite extension to cost 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), or £1,760–£2,380 per m² including VAT. Steelwork for wide openings is the item most likely to move the figure; we'll know once the engineer has designed it.
| Spec | Per m² | A 4 m × 3.5 m footprint on two floors (28 m² of new floor space) |
|---|---|---|
| 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 |
Planning and building control in Dundonald
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.
Design points for Dundonald homes
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.
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.
How we'd run your project
Free site visit
We visit your home in Dundonald, look at the structure, access and boundaries, and talk through what you want the new rooms to do.
Design and approvals
We draw the extension and check it against the rules for Northern Ireland, then apply for planning permission or a certificate of lawfulness, whichever fits.
Structure and building control
A structural engineer sizes the foundations and steels, and we get building regulations approval before work starts.
Build it
The new structure goes up first, then we open into the house, finish inside and get the completion certificate.
Questions about extra bedroom and en-suite extensions in Dundonald
Do I need planning permission for an extra bedroom and en-suite extension in Dundonald?
Dundonald 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.
Which postcodes do you cover around Dundonald?
We cover Dundonald (BT16) and nearby places including Holywood, Comber and Castlereagh, plus the rest of County Down. The first site visit is free.
How long does an extra bedroom and en-suite extension take?
Allow 4 to 8 weeks for survey and design, then the approval period (councils aim to decide local applications within an average of 15 weeks; many take longer), then 4 to 8 weeks of technical design, which can overlap. The build itself usually takes 14 to 20 weeks, longer for large or complex designs.
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.
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.
Nearby
The same service in neighbouring towns:
Other extensions in Dundonald
All two-storey extension services in Dundonald · Extra bedroom and en-suite extensions across County Down
Book a free site visit in Dundonald and we'll tell you what's possible, what approvals you need and what the design stage would cost.