Covering Harpenden
We work in Harpenden (AL5) and the places around it, including St Albans, Luton and Hemel Hempstead.
Homes in the East of England
Housing in the East of England ranges from post-war estates and modern developments to timber-framed and period homes in historic towns, so permitted development checks and conservation controls both feature regularly.
What is a double-storey extension?
Two-storey work has to sit comfortably with the house and the neighbours, so most of the design effort goes into the roofline, window positions and how the new first floor connects to the landing. We handle the planning application, the structural design and the building control process, then build, roof and finish both floors.
- Householder planning application
- Foundations, steelwork, brick and block walls, roof
- Windows, insulation, plastering, electrics and plumbing
What is the guide price for a double-storey extension in Harpenden?
Indicative costs for double-storey extensions. London and the South East usually sit towards the top of each range.
| Double-storey extensions | Guide price incl. VAT |
|---|---|
| Standard specification | £2,400 to £2,900 per m² |
| Good specification | £2,900 to £3,400 per m² |
| High specification | £3,400 to £3,850 per m² |
Planning and building rules in Harpenden
Projects in England go through two separate checks. Planning (or confirmation that the work is permitted development) comes from the district, borough or unitary council, and building regulations approval comes from the council’s building control team or a registered building control approver. Where work touches a shared wall or digs near a neighbour’s foundations, the Party Wall etc. Act 1996 applies.
Two-storey rear extensions can sometimes be permitted development in England (no more than 3 m deep, at least 7 m from the rear boundary, roof pitch to match), but most two-storey and all two-storey side extensions need householder planning permission. Expect around eight weeks for a decision once the application is validated.
What can affect a double-storey extension?
- Neighbours’ light is assessed using the 45-degree guide many councils use.
- The new roof is tied into the old one, so roof tiles and ridge details need to match.
From first call to completion
- Send us the details. Give us a postcode, a rough idea of size and some photos, by phone, form or the guide price tool.
- Survey at your house. We look at the existing structure, services and access, and agree what the design needs to achieve.
- Drawings, approvals, written quote. We prepare the design, apply for the approvals it needs, and give you a fixed price in writing.
- Build and hand over. Our teams build to the programme, building control inspects, and you get the completion paperwork at the end.
What people ask before starting
How much does a two-storey extension cost?
Typically about £2,400 to £3,850 per square metre of new floor area including VAT. A 40 m² extension across two floors is often around £100,000 to £150,000 depending on specification.
Will we need to move out?
Most people stay. The noisiest stage is when we break through into the existing first floor, which we plan for a short window.
Do you work in Harpenden?
Yes. Harpenden is within our coverage for double-storey extensions, along with nearby St Albans and Luton.
Double-storey extensions in nearby towns
- Double-storey extensions in St Albans
- Double-storey extensions in Luton
- Double-storey extensions in Hemel Hempstead
- Double-storey extensions in Welwyn Garden City
Learn more about double-storey extensions, or see every project we cover in Harpenden.