First-floor extensions in Antrim
Thinking about a first-floor extension in Antrim? We design it, take it through the approvals it needs and build it, with one team responsible from the first visit to the final certificate.
Quick reference for homeowners in Antrim.
- Postcode districts
- BT41
- County / area
- County Antrim, Northern Ireland
- Price region
- Northern Ireland
- Guide price
- £22,000–£32,000 (£1,580–£2,290 per m²)
- 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
- Randalstown (4.2 miles), Crumlin (County Antrim) (6.7 miles), Ballyclare (8.8 miles)
- Distance to Belfast
- about 14.1 miles
- First visit
- Free, no obligation
About a first-floor extension
A first-floor extension suits you if your house already has a single-storey extension and you need more space upstairs. You get a structural check of the existing walls and foundations, a design that ties the new floor into the house, the approvals your nation needs, building regulations approval and the build, managed by us and carried out by vetted teams working under S&K.
Around Antrim we also work in Randalstown, Crumlin (County Antrim) and Ballyclare, and across the rest of County Antrim. Postcode district in and near Antrim: BT41.
What it costs in Antrim
Most of the cost of a first-floor extension is set by its size and specification. For Antrim and the rest of Northern Ireland, our guide is £1,580–£2,290 per m² including VAT, so about £22,000–£32,000 for 4 m × 3.5 m of new first-floor space (14 m²). The fastest way to a firmer number is a free site visit, after which we price the design stage in writing.
| Spec | Per m² | 4 m × 3.5 m of new first-floor space (14 m²) |
|---|---|---|
| Essential | £1,460–£2,100 per m² | £20,500–£29,500 |
| Standard | £1,580–£2,290 per m² | £22,000–£32,000 |
| Premium | £1,900–£2,750 per m² | £26,500–£38,500 |
Planning and building control in Antrim
In Northern Ireland, a first floor over a rear extension can be permitted development if the extension goes no more than 3 m beyond the original rear wall and stays at least 7 m from the rear boundary, with height, materials and roof pitch conditions. Over a side extension, or beyond these limits, a planning application costs £347 per dwelling.
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 Antrim homes
Replacing the flat roof
The existing roof usually comes off and is replaced by a new first-floor structure. The room below is exposed for a short time, so we plan temporary weatherproofing and sequence the work to keep the kitchen or living room usable for as long as possible.
Tying into the house
The new floor and walls must line up with the existing first floor, often through a new opening in the rear wall above the old one. Floor levels, the position of upstairs windows and the existing roof all affect where the opening can go, so we survey both floors carefully.
How we'd run your project
Free site visit
We visit your home in Antrim, look at the structure, access and boundaries, and talk through what you want the new rooms to do.
Plans, then approval
Measured survey, design, then the right approval route for your house. We explain each step before we take it.
Fixed price in writing
With approved drawings and calculations, we give you a fixed build price and a programme you can plan around.
Build and sign-off
Vetted teams working under S&K build the extension, and we arrange the building control completion certificate at the end.
Questions about first-floor extensions in Antrim
How long does a first-floor 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 much does a first-floor extension cost in Antrim?
Our guide for Northern Ireland, which covers Antrim, is £1,580–£2,290 per m² including VAT. A typical project with 4 m × 3.5 m of new first-floor space (14 m²) comes to about £22,000–£32,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.
Who handles building control for a project in Antrim?
We handle it as part of the project. What's needed in Northern Ireland: building control approval from the local council under the Building Regulations (Northern Ireland), using the Technical Booklets. We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.
Can I build on top of my existing single-storey extension?
Often yes, but only after the structure has been checked. Foundations, walls and lintels built for one storey may not carry two. We dig trial holes, look for the original building control approval and ask the structural engineer to confirm what can stay, what needs strengthening and what must be rebuilt.
What happens to the room below while the first floor is built?
The old roof is removed, so the room below is exposed for a short period. We fit temporary weather protection, plan the work so the roof comes off only when the new structure is ready, and agree with you which rooms will be out of use and for roughly how long.
Nearby
Other towns near Antrim:
Other extensions in Antrim
- Rear
- Side
- Wraparound
- Part two-storey
- Over a garage
- Semi-detached
- Detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in Antrim · First-floor extensions across County Antrim
Tell us about your house in Antrim and we'll call you back to arrange a free, no-obligation visit.