Side return extensions in Harpenden
Thinking about a side return extension for your Harpenden home? Start with a free site visit: we measure up, check what the council will allow and give you honest guide figures on the day.
- Guide price in HarpendenFrom £19,000 inc VAT
- PlanningOften permitted development; party wall notice usual
- Build time10–14 weeks on site
- Postcode districtsAL5
How much does a side return extension cost in Harpenden?
These guide figures apply our East of England adjustment (×1.06) to national rates. They include VAT at 20% and cover the build itself; design and council fees are listed separately.
Typical rates in Harpenden: £2,230 to £4,030 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| 1.8 m × 4.5 m 8 m² | £19,000 – £23,000 | £20,000 – £25,500 | £25,000 – £32,500 |
| 2 m × 5.5 m 11 m² | £24,000 – £29,500 | £27,500 – £35,000 | £34,500 – £44,500 |
| 2.2 m × 7 m 15 m² | £33,000 – £40,000 | £38,000 – £48,000 | £47,500 – £60,500 |
Try the guide-price tool to see a range for your own size and finish.
Will the council need to approve it?
In England a single-storey side return infill is often permitted development if it stays within the height limits and is no wider than half the width of the original house. Conservation areas, listed buildings and flats always need an application, and the boundary wall usually brings in the Party Wall Act.
In a conservation area, national park, National Landscape, the Broads or a World Heritage Site the permitted development limits are tighter (no side or two-storey extensions without an application). Listed homes need listed building consent, and if permitted development rights have been removed, any extension needs an application.
Building regulations approval is separate from planning. In England you can use the council's building control team or a registered building control approver; a full plans application gets the drawings checked before work starts, and the inspector signs the work off with a completion certificate.
If the work involves a shared wall, building on the boundary, or digging foundations within 3 m (sometimes 6 m) of a neighbour's building, the Party Wall etc. Act 1996 applies and notice must be served before work starts: two months for work to a party wall, one month for new walls on the boundary and for excavations.
Applications are decided by the local planning authority (your district, borough or unitary council).
Included in a typical project
- Party wall notice support (England and Wales)
- Removal of the side wall and new steelwork
- Survey of the outrigger, boundary wall and drainage
- New boundary wall or raised party wall
Extensions in and around Harpenden
Site visits are available across Harpenden (AL5). Neighbouring towns we cover include St Albans (5 miles), Hemel Hempstead (6 miles), Welwyn Garden City (6 miles), Hatfield (7 miles).
For homes towards Bedfordshire, Luton is around 5 miles away. The East of England mixes market-town terraces, inter-war semis and modern estates. Clay soils are common in parts of the region, which can affect foundation design.
From first visit to completion
Site visits are free and there is no obligation. Where drawings are needed, the design stage is priced in writing before it starts.
Free site visit
First, a site visit: we look at the house, garden, access and drains and listen to what you need.
Design and approvals
We draw the design, agree it with you and handle planning or permitted development checks and building regulations.
Fixed written price
You receive a written, itemised price and programme. Nothing starts until you are happy with it.
Build and sign-off
We build it with one project manager, book the building control inspections and hand over the completion certificate.
Side return extension questions answered
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Harpenden, and the guide-price tool gives a range for your own size. After the survey you get a written price before anything is agreed.
Will my neighbours in Harpenden be involved?
If a planning application or prior approval is needed, the council notifies neighbours. If the work is on or near a shared boundary, party wall notices may also be needed.
Do I need building regulations approval in Harpenden?
Yes. Almost every extension needs it, whatever the planning route. We prepare the drawings and book the inspections.
How much does a side return extension cost?
Our guide range is about £2,230 to £4,030 per m² including VAT, so a typical 2 m × 5.5 m infill lands around £27,500 to £35,000 at standard spec in Harpenden, more in London.
Will the kitchen be darker?
Not if the roof is designed well. A glazed roof or a line of rooflights along the boundary usually makes the room brighter than before.
Book a free site visit in Harpenden
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.