Double-storey extensions for homes in Castlereagh
A double-storey extension in Castlereagh starts with the right design and the right approval route. We take care of both, then build it with our own project management.
- Guide price in CastlereaghFrom £32,500 inc VAT
- PlanningUsually needs planning permission
- Build time16–24 weeks on site
- Postcode districtsBT1, BT2, BT4, BT5, BT6
Planning and approvals in Castlereagh
In Northern Ireland the Planning (General Permitted Development) Order 2015 lets some single-storey rear extensions go ahead without planning permission, up to 3 m on a semi-detached or terraced house and 4 m on a detached house, within height and boundary limits. Larger, side and two-storey extensions normally need planning permission from the council, and building control approval is separate.
Homes in conservation areas, areas of townscape character and listed buildings have tighter rules, so we always check the property's status and planning history before design starts.
Building close to a public sewer needs the agreement of NI Water, which we check during design.
In Northern Ireland building control is run by the councils under the Building Regulations (Northern Ireland). We submit full plans or a building notice and book the inspections through to completion.
Applications are decided by your council, which handles local planning in Northern Ireland.
Covering Castlereagh
Postcode districts we cover around Castlereagh include BT1, BT2, BT4, BT5, BT6, BT7. The same team covers Belfast (2 miles), Newtownabbey (6 miles), Lisburn (7 miles), Carrickfergus (10 miles), all within easy reach.
For homes towards County Down, Newtownards is around 8 miles away. Northern Ireland's housing ranges from city terraces to large numbers of detached houses and bungalows on rural plots, many in render, where single-storey extensions fit easily.
Double-storey extension prices in Castlereagh
Labour and material costs vary across the UK, so for Castlereagh we use our Northern Ireland factor (×0.86). The ranges include VAT and exclude design, structural and council fees.
Typical rates in Castlereagh: £1,330 to £2,580 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| 3 m × 4 m, two floors 24 m² | £32,500 – £39,500 | £37,000 – £49,000 | £47,000 – £62,000 |
| 4 m × 4 m, two floors 32 m² | £42,500 – £51,000 | £49,500 – £65,000 | £63,000 – £83,000 |
| 4 m × 6 m, two floors 48 m² | £63,500 – £76,500 | £74,000 – £97,500 | £94,500 – £124,000 |
Try the guide-price tool to see a range for your own size and finish.
What is included
- Breaking through at both levels, stairs and landing changes where needed
- Measured survey, design and planning drawings
- Ground and first floor structure, roof tied into the existing roof
- Building regulations drawings and structural design
- Insulation, plastering, electrics and plumbing to finish
How the project works
Site visits are free and there is no obligation. Where drawings are needed, the design stage is priced in writing before it starts.
Free site visit
We visit your Castlereagh home, measure up, talk through what you want and check the planning position.
Design and approvals
We draw the design, agree it with you and handle planning or permitted development checks and building regulations.
Fixed written price
With the design and specification agreed, you get a fixed written price and a start date.
Build and sign-off
Work is carried out to the agreed programme, inspected by building control and signed off at the end.
Common questions in Castlereagh
Will my neighbours in Castlereagh be involved?
If a planning application is needed, the council notifies neighbours. Where work is close to a shared boundary, we agree access and protection with them in writing.
Do you cover all of Castlereagh?
Yes. We cover Castlereagh and the surrounding parts of County Antrim. Site visits are free and there is no obligation.
Do I need building regulations approval in Castlereagh?
Yes. Almost every extension needs it, whatever the planning route. We prepare the drawings and book the inspections.
Is a two-storey extension cheaper per square metre?
Usually. Our guide range is about £1,330 to £2,580 per m² of new floor area including VAT, compared with £1,500 to £2,920 per m² for single-storey work, because the foundations and roof are shared across two floors.
Book a free site visit in Castlereagh
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.