Harpenden, Hertfordshire
Glazed rear extension in Harpenden
We plan and build glazed and glass-box rear extensions for homeowners in Harpenden. Full-height glass, slim frames and big rooflights for the most open rear room. Start with a free site visit, then a written price once the design is agreed.
We cover Harpenden (AL5) as part of our Hertfordshire work. If your garden in Harpenden faces south, expect us to talk about overhangs and solar-control glass before frame colours.
Book a free site visit
Tell us about the house and we'll call to arrange a free, no-obligation visit.
How much does a glazed rear extension cost in Harpenden?
A glazed rear extension in Harpenden is priced at £2,970–£5,090 per square metre including VAT as a guide, before kitchen fit-out and fees. East of England prices run slightly above our West Midlands baseline; clay soils near trees are the main foundation variable.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £35,500–£61,000 |
| 4 m wide × 6 m deep (24 m²) | £71,000–£122,000 |
Your written price follows a measured survey and an agreed design, so it reflects your house, not an average.
Do you need planning permission for a glazed rear extension in Harpenden?
Planning for a glazed rear extension in Harpenden follows the English householder rules.
English permitted development (Class A) allows a single-storey rear extension of 3 metres on a terraced or semi-detached house and 4 metres on a detached one, measured from the original house, with a maximum height of 4 metres and eaves of no more than 3 metres within 2 metres of a boundary.
New fabric must meet Approved Document L (2021 edition incorporating 2023 amendments): walls 0.18, roof 0.15 and floor 0.18 W/m²K, windows 1.4 W/m²K or Band B. Under the simple route, new windows, doors and rooflights should not exceed 25% of the extension floor area plus any openings removed; more glass is possible with a whole-house calculation.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent. We check your house's planning history and any conservation area before drawing, so the route is clear before you spend on plans.
What are homes in Harpenden like to extend?
Harpenden mixes Victorian terraces with 1930s semis, so both side returns and full-width kitchen extensions suit houses here.
How a glazed rear extension in Harpenden comes together
Survey visit
We visit free of charge, measure up, check access, drainage and neighbours' extensions, and note what you want the room to do.
Drawings and budget
Floor plans and elevations for the options, each with a guide price.
Paperwork handled
Planning, prior approval or permitted development, Building Regulations approval, structural design and party wall notices are all handled by us.
Written price, then build
Once the design and approvals are in place, you get a fixed written price and programme, and we build through to sign-off.
Glazed rear extensions near Harpenden
Close by, we work in St Albans, about 4.7 miles away, and Luton, about 5.0 miles away.
- Glazed rear extension in St Albans
- Glazed rear extension in Luton
- Glazed rear extension in Codicote
- Glazed rear extension in Hemel Hempstead
- Glazed rear extension in Welwyn Garden City
Other work in Harpenden:
FAQ
Glazed rear extension questions in Harpenden
Can I get a price without a visit?
Our online guide-price tool gives a range in a couple of minutes. A written price needs a survey.
What postcode areas do you cover around Harpenden?
Including AL5, and the surrounding Hertfordshire area.
Can I have a level threshold?
Yes, with a drainage channel outside the doors and the slab set to the patio level.
How long does a rear extension take to build in Harpenden?
Most single-storey rear extensions take 10 to 16 weeks on site and two-storey extensions 16 to 26 weeks, after design and approvals.
Do you handle building control in Harpenden?
Yes. We apply to the council or a registered building control approver and hand over the completion certificate.
Who will build my extension?
Vetted building teams working under contract to us. Your contract is with S&K Property Investments and Improvement Ltd for the design and the build.