What is a glazed extension?
A glazed or contemporary extension uses large panes of glass, slim aluminium frames and modern cladding to create a bright room that contrasts with the original house. Frameless corners, structural glass roofs and minimal sliding doors are typical features.
How much does a glazed extension cost in Northamptonshire?
In Northamptonshire, a glazed extension typically costs £2,650–£4,000 per m² of floor area, including VAT at 20% (standard rate). For a typical 18 m² project that is roughly £47,500–£72,000. We start from a UK-wide guide and adjust it for the East Midlands, where labour and materials are typically about 5% below average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (13 m²) | £34,500–£52,000 |
| Typical project (18 m²) | £47,500–£72,000 |
| Larger project (25 m²) | £66,000–£100,000 |
| Rate per m² | £2,650–£4,000 |
The biggest cost drivers are:
- Glazing size, specification and lead time
- Cladding material
- Lighting and finishes
- Access for large glass panels
Your exact price depends on the survey and drawings. The guide price tool gives a quick range in the meantime.
Do you need planning permission for a glazed extension in Northamptonshire?
Whether you need planning permission depends on your house and its location in England. In England a single-storey rear extension is often permitted development: broadly up to 3 metres deep on a semi-detached or terraced house and 4 metres on a detached house, no higher than 4 metres, with eaves no higher than 3 metres within 2 metres of a boundary, and covering no more than half the garden. The larger home extension scheme allows up to 6 or 8 metres if you notify the council first and neighbours have a chance to comment. In conservation areas, National Parks and National Landscapes the larger home extension route, side extensions and cladding are not permitted development. Flats and houses whose rights have been removed need a planning application, and listed buildings need listed building consent.
Building regulations approval comes from the council’s building control service or a registered building control approver. The work is inspected at key stages, such as foundations, drainage and insulation, and a completion certificate is issued at the end.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
What we take care of:
- Building control sign-off
- Structural design for steel frames and glass supports
- Large-format sliding doors and fixed glazing
- Foundations, walls and insulated roof
- Cladding or render finish
- Electrics, heating and finishes
How long does it take?
Build time is typically 12 to 16 weeks on site; glazing lead times can be 6 to 10 weeks. Design and approvals come first and typically take 3 to 4 months, depending on the approval route.
Building in Northamptonshire
The East Midlands has a mix of red-brick terraces, inter-war semis and newer estates, so rear extensions and garage conversions are common projects.
Towns we cover in Northamptonshire include Northampton, Corby, Kettering, Wellingborough, Rushden and Daventry.
How it works
- 01
Free visit
We look at the property, talk through what you want and measure up. There is no charge and no obligation.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 04
Build and sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about glazed extensions in Northamptonshire
Can large glass panels be lifted in?
Some need a crane or glass-lifting robot. We plan access during design.
How much does a glazed extension cost in Northamptonshire?
In Northamptonshire, a glazed extension typically costs £2,650–£4,000 per m² of floor area, including VAT at 20% (standard rate). A typical 18 m² project comes to roughly £47,500–£72,000. Your fixed price depends on the survey and drawings.
Do you build glazed extensions in Northamptonshire?
Yes. We build glazed extensions across Northamptonshire, including postcodes CV23, LE15, LE16, MK19 and NN1. Every project starts with a free home visit.
Will a glass extension be too hot in summer?
It can be if poorly designed. Solar-control glass, roof overhangs and opening vents reduce overheating, and building regulations may require calculations to show the design works.
Is triple glazing necessary?
Not always. High-performance double glazing can meet the standards; triple glazing helps in exposed locations.