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 Truro?
In Truro, a glazed extension typically costs £2,850–£4,300 per m² of floor area, including VAT at 20% (standard rate). For a typical 18 m² project that is roughly £51,500–£77,500. Building costs in the South West are close to the UK average, so the figures for Truro are close to our national guide. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (13 m²) | £37,000–£56,000 |
| Typical project (18 m²) | £51,500–£77,500 |
| Larger project (25 m²) | £71,000–£107,500 |
| Rate per m² | £2,850–£4,300 |
The main things that change the cost:
- Overheating and energy design
- Steel framing
- Cladding material
- Access for large glass panels
Use the guide price tool to see how size and specification change the figure, then ask for a written, itemised quote.
Do you need planning permission for a glazed extension in Truro?
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.
Our first visit includes a check of your planning history, so you know the route before paying for drawings.
What we handle
From survey to sign-off, the job normally involves:
- Contemporary design and planning drawings
- Building control sign-off
- Large-format sliding doors and fixed glazing
- Foundations, walls and insulated roof
- Energy and overheating calculations where needed
- Cladding or render finish
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 Truro
The South West mixes stone and render cottages with post-war and newer estates, and local materials matter more here when matching an extension.
From TR1 outwards, we take on projects throughout Truro and the surrounding parts of Cornwall.
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
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about glazed extensions in Truro
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.
Does it need planning permission?
The same rules as other extensions apply, but contemporary designs in conservation areas are assessed carefully. We discuss the design approach with you before applying.
How much does a glazed extension cost in Truro?
In Truro, a glazed extension typically costs £2,850–£4,300 per m² of floor area, including VAT at 20% (standard rate). A typical 18 m² project comes to roughly £51,500–£77,500. Your fixed price depends on the survey and drawings.
Is triple glazing necessary?
Not always. High-performance double glazing can meet the standards; triple glazing helps in exposed locations.
How long does a glazed extension take in Truro?
Typically 12 to 16 weeks on site; glazing lead times can be 6 to 10 weeks. Design and approvals beforehand usually take 3 to 4 months.