Double-storey extensions in Carrickfergus
A double-storey extension in Carrickfergus 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 CarrickfergusFrom £32,500 inc VAT
- PlanningUsually needs planning permission
- Build time16–24 weeks on site
- Postcode districtsBT38
Will the council need to approve it?
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.
Before any drawing is finalised we check whether the house is listed, in a conservation area or subject to an Article 4 direction.
Building close to a public sewer needs the agreement of NI Water, which we check during design.
Northern Ireland has no Party Wall Act. Where work is on or close to a shared boundary, we agree access and protection with your neighbour in writing before work starts.
Applications are decided by your council, which handles local planning in Northern Ireland.
When a double-storey extension makes sense
- Growing families who need a bedroom as well as a bigger kitchen
- Homeowners who would otherwise consider moving
- Houses with enough distance to the rear or side boundary
Local to Carrickfergus
Across BT38, we can visit, measure and advise. The same team covers Newtownabbey (6 miles), Larne (9 miles), Belfast (10 miles), Castlereagh (10 miles), all within easy reach.
Just over the County Down border, Bangor, County Down is about 7 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.
How much does a double-storey extension cost in Carrickfergus?
These guide figures apply our Northern Ireland adjustment (×0.86) to national rates. They include VAT at 20% and cover the build itself; design and council fees are listed separately.
Typical rates in Carrickfergus: £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 |
Want a range for your exact size? The guide-price tool takes about a minute.
From first visit to completion
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 Carrickfergus home, measure up, talk through what you want and check the planning position.
Design and approvals
Once the layout is agreed, we deal with the council: planning permission or written confirmation that none is needed, plus building control.
Fixed written price
The price is fixed in writing once the design is settled, with a clear programme and payment stages.
Build and sign-off
Our team builds the extension, keeps you updated weekly and finishes with building control sign-off.
Questions people ask about double-storey extensions
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Carrickfergus, and the guide-price tool gives a range for your own size. After the survey you get a written price before anything is agreed.
How long does a double-storey extension take to build in Carrickfergus?
On site, typically 16 to 24 weeks once approvals are in place. Before that, allow 8–16 weeks design and approvals.
Do you cover all of Carrickfergus?
Yes. We cover Carrickfergus and the surrounding parts of County Antrim. Site visits are free and there is no obligation.
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 Carrickfergus
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.