Two-storey extensions in Harpenden
Homeowners in Harpenden can use us for the whole project or just the drawings and approvals. Start with a free visit.
Harpenden at a glance
- Postcode districts
- AL5
- Area
- Hertfordshire, England
- Price region
- East of England
- Nearest towns
- St Albans (4.7 miles), Luton (5.1 miles), Codicote (5.6 miles), Leverstock Green (5.7 miles)
- Distance to Watford
- about 11.3 miles
- Approvals
- Two-storey rear: up to 3 m deep and 7 m from the rear boundary under permitted development. Side, wraparound and front: planning permission.
Around Harpenden we also work in St Albans, Luton and Codicote, and across the rest of Hertfordshire. Postcode district in and near Harpenden: AL5.
Extensions available in Harpenden
Two-storey rear extensions
Guide from £57,500 in Harpenden, including VAT.
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Two-storey side extensions
Our East of England guide starts at £88,500 for this type.
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Two-storey wraparound extensions
Guide from £124,000 in Harpenden, including VAT.
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Part single, part two-storey extensions
Guide from £74,000 in Harpenden, including VAT.
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Extensions over a garage
From £32,500 in Harpenden. Free visit to firm it up.
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First-floor extensions
Design, approvals and build for Harpenden homes. Guide from £26,000.
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Two-storey extensions for semi-detached houses
Design, approvals and build for Harpenden homes. Guide from £57,500.
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Two-storey extensions for detached houses
For homes in Harpenden: typical guide from £88,500.
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Kitchen extensions with bedrooms above
From £57,500 (before kitchen units) in Harpenden. Free visit to firm it up.
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Extra bedroom and en-suite extensions
Guide from £57,500 (plus en-suite) in Harpenden, including VAT.
Learn moreWhich type suits your house?
Which type suits your house in Harpenden depends mostly on where you have room. A deep garden points to a rear extension; space beside the house points to a side or over-garage extension; a house that already has a single-storey extension can often take a first floor on top.
Also available in Hertfordshire
- Two-storey front extensions
- Two-storey extensions for end-of-terrace houses
- Two-storey annexe extensions
- Garage conversions with a room above
- Two-storey extension plans and drawings
- Planning permission for two-storey extensions
- Structural engineering for two-storey extensions
- Building regulations for two-storey extensions
- Party wall notices for extensions
- Design and build two-storey extensions
Rules for Harpenden
Harpenden is in England. Two-storey rear: up to 3 m deep and 7 m from the rear boundary under permitted development. Side, wraparound and front: planning permission. Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.
The full England rules explained
Questions about extensions in Harpenden
Do you cover Harpenden?
Yes. We cover Harpenden (AL5) and the surrounding area, including St Albans and Luton. The first site visit is free.
What does a two-storey extension cost in Harpenden?
Using our East of England guide, a two-storey rear extension with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) is about £57,500–£78,000 including VAT. An extension over a garage is about £32,500–£47,500.
Which other places near Harpenden do you cover?
Everywhere around it, including St Albans (4.7 miles), Luton (5.1 miles) and Codicote (5.6 miles), and the rest of Hertfordshire.