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 Barnet?
In Barnet, a glazed extension typically costs £3,650–£5,450 per m² of floor area, including VAT at 20% (standard rate). For a typical 18 m² project that is roughly £65,500–£98,000. We start from a UK-wide guide and adjust it for London, where labour and materials are typically about 30% above average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (13 m²) | £47,500–£71,000 |
| Typical project (18 m²) | £65,500–£98,000 |
| Larger project (25 m²) | £91,000–£136,000 |
| Rate per m² | £3,650–£5,450 |
Your quote will depend mainly on:
- Lighting and finishes
- Glazing size, specification and lead time
- Overheating and energy design
- Access for large glass panels
For a figure based on your own measurements, try the guide price tool, then book a free home visit for a fixed quote.
Do you need planning permission for a glazed extension in Barnet?
The approval route for Barnet is set by planning law 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
Handled as part of most glazed extensions:
- Cladding or render finish
- Energy and overheating calculations where needed
- Foundations, walls and insulated roof
- Building control sign-off
- Electrics, heating and finishes
- Large-format sliding doors and fixed glazing
How long does it take?
Build time is typically 12 to 16 weeks on site; glazing lead times can be 6 to 10 weeks. Before that, surveys, drawings and approvals usually take 3 to 4 months, longer if the council asks for changes.
Building in Barnet
Space is at a premium in London, so homeowners often build out into the side return or up into the roof rather than move.
If your home is in Barnet or close by in Potters Bar, Mill Hill and Borehamwood, a free home visit is the first step.
How it works
- 01
Visit and measured survey
A free visit to understand the project, check access and take measurements.
- 02
Drawings and written quote
We prepare the design and give you a written, itemised quote with inclusions and exclusions.
- 03
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about glazed extensions in Barnet
Who approves a glazed extension in Barnet?
Planning matters in Barnet go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
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.
How long do large glass panels take to arrive?
Often 6 to 10 weeks after final measurements, so we order them as soon as the structure is built.
How much does a glazed extension cost in Barnet?
In Barnet, a glazed extension typically costs £3,650–£5,450 per m² of floor area, including VAT at 20% (standard rate). A typical 18 m² project comes to roughly £65,500–£98,000. Your fixed price depends on the survey and drawings.