Harpenden, Hertfordshire
Rear extension planning drawings in Harpenden
We plan and build rear extensions for homeowners in Harpenden. Measured survey, design options, planning drawings and the application, handled for you. 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. Rear extension applications in Hertfordshire are householder applications, which councils aim to decide within about eight weeks.
Book a free site visit
Tell us about the house and we'll call to arrange a free, no-obligation visit.
What do rear extension planning drawings cost in Harpenden?
As a guide, £1,000–£2,500 including VAT for a single-storey rear extension, or £2,000–£3,500 for a two-storey scheme. A householder planning application in England costs £548 (£575 for applications made from 8 December 2026), and a lawful development certificate for proposed work costs half the householder fee. These are guide ranges; the written quote after the survey is the figure that counts.
Do you need planning permission for a rear extension in Harpenden?
The planning route for a rear extension in Harpenden is set by England's householder rules and your council.
A two-storey rear extension can be permitted development in England only if it projects no more than 3 metres, stays at least 7 metres from the rear boundary, matches the existing roof pitch and has obscure-glazed upper side windows. In practice most double-storey rear extensions go through a householder planning application.
Councils aim to decide householder applications within 8 weeks of validation, and prior approval within 42 days.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent. At the first visit we measure what is there now and tell you which route fits: permitted development, prior approval or a planning application.
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 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.
Rear extension planning drawings near Harpenden
We also build rear extensions in nearby St Albans (4.7 miles) and Luton (5.0 miles).
- Rear extension planning drawings in St Albans
- Rear extension planning drawings in Luton
- Rear extension planning drawings in Codicote
- Rear extension planning drawings in Hemel Hempstead
- Rear extension planning drawings in Welwyn Garden City
Other work in Harpenden:
FAQ
Rear extension planning drawings questions in Harpenden
Will I need a structural engineer?
Yes for the beam over the new opening and usually the foundations; we arrange them and their calculations go to building control.
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.
Do neighbours get consulted?
Yes for a full application: the council writes to them or puts up a site notice.
Can I live at home while the extension is built?
Usually yes. Most of the work is outside until the back wall is opened near the end, and that stage is screened off.
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.
Do I need planning permission for a rear extension in Harpenden?
Often not for a single-storey rear extension of up to 3 metres (4 metres on a detached house) under permitted development, or up to 6 or 8 metres with prior approval, unless the house is in a conservation area or its rights have been removed.