Antrim annexe extensions, designed and built
Our design and build teams take on annexe extensions in Antrim, from the first measured survey through planning and building control to the finished room.
- Guide price in AntrimFrom £47,000 inc VAT
- PlanningUsually needs planning permission
- Build time16–24 weeks on site
- Postcode districtsBT41
Working in Antrim
Site visits are available across Antrim (BT41). The same team covers Ballymena (10 miles), Newtownabbey (13 miles), Belfast (14 miles), Lisburn (15 miles), all within easy reach.
Magherafelt, in County Londonderry, is roughly 17 miles from Antrim and also on our list. In Northern Ireland, extension projects follow the NI planning rules and council building control, which we account for from the first survey.
Planning and approvals in Antrim
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.
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.
What should I budget for an annexe extension in Antrim?
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 Antrim: £1,720 to £3,270 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| Studio annexe 25 m² | £47,000 – £59,500 | £51,500 – £64,500 | £64,500 – £82,000 |
| One-bedroom annexe 35 m² | £60,000 – £75,500 | £72,000 – £90,500 | £90,000 – £114,500 |
| Larger annexe 45 m² | £77,000 – £97,000 | £92,500 – £116,500 | £116,000 – £147,500 |
Try the guide-price tool to see a range for your own size and finish.
Is an annexe extension right for your house?
- Multi-generational families
- Relatives who need support close by
- Homes with a large side or rear garden
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
A designer visits, takes measurements and photos, and discusses layouts, budget and timing with you.
Design and approvals
Drawings are prepared and agreed with you, then submitted for the right planning route and building regulations approval.
Fixed written price
You receive a written, itemised price and programme. Nothing starts until you are happy with it.
Build and sign-off
The build is managed from start to finish, inspected at each stage and signed off on completion.
Common questions in Antrim
Will my neighbours in Antrim 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.
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Antrim, 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 an annexe extension take to build in Antrim?
On site, typically 16 to 24 weeks once approvals are in place. Before that, allow 10–16 weeks design and approvals.
How much does an annexe extension cost?
Our guide range is about £1,720 to £3,270 per m² including VAT. A one-bedroom annexe of about 35 m² is typically £72,000 to £90,500 at standard spec in Antrim.
Does an annexe extension need planning permission?
Usually yes, because of its size and the way it will be used. Councils check that it stays ancillary to the main house, so the application must describe the use clearly.
Book a free site visit in Antrim
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.