Glass box extensions in Belfast: design, approvals and build
A glass extension in Belfast 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 BelfastFrom £25,500 inc VAT
- PlanningNI permitted development (rear 3–4 m) or planning
- Build time10–16 weeks on site
- Postcode districtsBT1, BT2, BT6, BT7, BT12
How much does a glass extension cost in Belfast?
Prices below are for Belfast, using the Northern Ireland factor of ×0.86. They are guide ranges including VAT for the build only, not a quote.
Typical rates in Belfast: £2,580 to £4,990 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| 2 m × 4 m 8 m² | £25,500 – £31,000 | £25,500 – £32,500 | £29,500 – £40,000 |
| 3 m × 4 m 12 m² | £30,500 – £37,500 | £36,000 – £45,500 | £44,000 – £60,000 |
| 3 m × 6 m 18 m² | £46,000 – £56,000 | £54,000 – £68,500 | £66,500 – £90,000 |
For a figure based on your own dimensions, use our guide-price tool.
Planning and approvals in Belfast
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.
Is a glass extension right for your house?
- Small infill spaces and side returns
- Period and listed-style houses where a light touch is wanted
- Garden-facing dining rooms
Local to Belfast
We cover Belfast and the postcode districts BT1, BT2, BT6, BT7, BT12, BT13. Neighbouring towns we cover include Castlereagh (2 miles), Newtownabbey (4 miles), Lisburn (7 miles), Carrickfergus (10 miles).
Newtownards, in County Down, is roughly 9 miles from Belfast 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.
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
First, a site visit: we look at the house, garden, access and drains and listen to what you need.
Design and approvals
We draw the design, agree it with you and handle planning or permitted development checks and building regulations.
Fixed written price
We confirm the build price in writing, based on the approved drawings and the finishes you have chosen.
Build and sign-off
The build is managed from start to finish, inspected at each stage and signed off on completion.
Common questions in Belfast
Who do I contract with for a glass extension in Belfast?
Your contract is with S&K Property Investments and Improvement Ltd, which designs and manages the project and the build teams who carry it out.
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Belfast, and the guide-price tool gives a range for your own size. After the survey you get a written price before anything is agreed.
Do I need building regulations approval in Belfast?
Yes. Almost every extension needs it, whatever the planning route. We prepare the drawings and book the inspections.
How much does a glass extension cost?
Our guide range is about £2,580 to £4,990 per m² including VAT, because structural glass is made to order. A 12 m² standard-spec glass extension is typically £36,000 to £45,500 in Belfast.
Are glass extensions cold in winter?
Modern double or triple glazing with warm-edge spacers and underfloor heating keeps them comfortable. They are not as warm as a solid room, and we explain the trade-off honestly.
Book a free site visit in Belfast
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.