Two-storey extensions in Welwyn Garden City
From over-garage bedrooms to full wraparounds, we cover every kind of two-storey extension in Welwyn Garden City.
Welwyn Garden City at a glance
- Postcode districts
- AL6, AL7 and AL8
- Area
- Hertfordshire, England
- Price region
- East of England
- Nearest towns
- Hatfield (2.8 miles), Codicote (3.6 miles), Hertford (5.5 miles), St Albans (6.5 miles)
- Distance to Watford
- about 13 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 Welwyn Garden City we also work in Hatfield, Codicote and Hertford, and across the rest of Hertfordshire. Postcode districts in and near Welwyn Garden City: AL6, AL7 and AL8.
Extensions available in Welwyn Garden City
Two-storey rear extensions
From £57,500 in Welwyn Garden City. Free visit to firm it up.
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Two-storey side extensions
Welwyn Garden City guide price from £88,500, Standard spec.
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Two-storey wraparound extensions
Welwyn Garden City guide price from £124,000, Standard spec.
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Part single, part two-storey extensions
For homes in Welwyn Garden City: typical guide from £74,000.
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Extensions over a garage
Welwyn Garden City guide price from £32,500, Standard spec.
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First-floor extensions
For homes in Welwyn Garden City: typical guide from £26,000.
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Two-storey extensions for semi-detached houses
Our East of England guide starts at £57,500 for this type.
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Two-storey extensions for detached houses
For homes in Welwyn Garden City: typical guide from £88,500.
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Kitchen extensions with bedrooms above
From £57,500 (before kitchen units) in Welwyn Garden City. Free visit to firm it up.
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Extra bedroom and en-suite extensions
Our East of England guide starts at £57,500 (plus en-suite) for this type.
Learn moreWhich type suits your house?
Rear, side, wraparound or over the garage: each adds space in a different way. For most houses in Hertfordshire, one or two of these will clearly suit the plot better than the rest, and we'll tell you which.
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 Welwyn Garden City
Welwyn Garden City 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 Welwyn Garden City
Do you cover Welwyn Garden City?
Yes. We cover Welwyn Garden City (AL6, AL7 and AL8) and the surrounding area, including Hatfield and Codicote. The first site visit is free.
What does a two-storey extension cost in Welwyn Garden City?
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 Welwyn Garden City do you cover?
Everywhere around it, including Hatfield (2.8 miles), Codicote (3.6 miles) and Hertford (5.5 miles), and the rest of Hertfordshire.