Two-storey extensions for semi-detached houses in Kilkeel
We plan and build two-storey extensions for semi-detached houses for homeowners in Kilkeel and nearby. Every project starts with a free visit and a design stage priced in writing before any work begins.
Useful details for planning a two-storey extension for a semi-detached house in Kilkeel.
- Postcode districts
- BT34
- County / area
- County Down, Northern Ireland
- Price region
- Northern Ireland
- Guide price
- £49,500–£66,500 (£1,760–£2,380 per m²)
- Approval route
- Depends on position: a two-storey rear extension may be permitted development (3 m deep, 7 m from the rear boundary); most others need planning permission.
- Nearest towns
- Warrenpoint (10.7 miles), Newcastle (11.7 miles), Newry (15.7 miles)
- Distance to Bangor (County Down)
- about 43.5 miles
- First visit
- Free, no obligation
About a two-storey extension for a semi-detached house
This service suits you if you own a semi-detached house and want to add bedrooms and living space without moving. On a semi, the main questions are which side to build on and how to treat the attached neighbour. You get a survey, design options, the approvals your nation needs and the build, carried out by vetted teams working under S&K.
Around Kilkeel we also work in Warrenpoint, Newcastle and Newry, and across the rest of County Down. Postcode district in and near Kilkeel: BT34.
What it costs in Kilkeel
Most of the cost of a two-storey extension for a semi-detached house is set by its size and specification. For Kilkeel and the rest of Northern Ireland, our guide is £1,760–£2,380 per m² including VAT, so about £49,500–£66,500 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). The fastest way to a firmer number is a free site visit, after which we price the design stage in writing.
| 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 Kilkeel
In Northern Ireland, a two-storey rear extension on a semi can be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary, with height, materials and roof pitch conditions. Upper side windows within 15 m of a boundary must be obscure and non-opening. A side extension normally needs planning, costing £347.
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 Kilkeel homes
The attached neighbour's light
A two-storey rear extension next to the party wall can take light from the neighbour's rear windows. Councils often use a 45-degree test, so the first floor may need to be shorter than the ground floor or set in from the shared boundary.
Keeping the pair balanced
Semis are designed as matching pairs, and a side extension changes that balance. Setting the side extension back from the front wall and keeping its ridge lower helps the pair still read as a pair, which councils' design guides commonly ask for.
How we'd run your project
Free site visit
We visit your home in Kilkeel, 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.
Finish and certify
Second fix, plastering and making good, then building control's final inspection and the completion paperwork.
Questions about two-storey extensions for semi-detached houses in Kilkeel
How much does a two-storey extension for a semi-detached house cost in Kilkeel?
Our guide for Northern Ireland, which covers Kilkeel, is £1,760–£2,380 per m² including VAT. A typical project with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) comes to about £49,500–£66,500. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.
Do I need planning permission for a two-storey extension for a semi-detached house in Kilkeel?
Kilkeel is in Northern Ireland. Depends on position: a two-storey rear extension may be permitted development (3 m deep, 7 m from the rear boundary); most others need planning permission.
Which postcodes do you cover around Kilkeel?
We cover Kilkeel (BT34) and nearby places including Warrenpoint, Newcastle and Newry, plus the rest of County Down. The first site visit is free.
Does a two-storey extension add value to a semi-detached house?
It usually adds value, but the gain is never certain. Nationwide's 2025 research found that 10% more floor area was linked to about 5% higher value, and that adding a double bedroom and bathroom to a three-bed, one-bathroom house could add up to 24%. Every street has a ceiling price, so check local sales first.
What if my neighbour has already extended?
That often helps. An existing extension next door can reduce the effect of yours on their light, and may show what the council accepts on your street. It can also mean building alongside their wall, so we check its position, foundations and any windows facing your plot at the survey.
Nearby
Close to Kilkeel? We work across the area, including:
Other extensions in Kilkeel
- Rear
- Side
- Wraparound
- Part two-storey
- Over a garage
- First floor
- Detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in Kilkeel · Two-storey extensions for semi-detached houses across County Down
Send us your postcode and a few details. We'll get back to you to arrange a visit and talk through your options.