Single-storey rear extensions in Watford: design, approvals and build
A single-storey extension in Watford starts with the right design and the right approval route. We take care of both, then build it with our own project management.
- Guide price in WatfordFrom £22,000 inc VAT
- PlanningOften permitted development (3–4 m), or prior approval up to 6–8 m
- Build time10–16 weeks on site
- Postcode districtsWD1, WD2, WD17, WD18, WD23
Local to Watford
Our survey diary covers Watford, including WD1, WD2, WD17, WD18, WD23, WD24. Neighbouring towns we cover include Bushey (2 miles), Rickmansworth (4 miles), Borehamwood (5 miles), St Albans (7 miles).
For homes towards Greater London, Pinner is around 4 miles away. Across the East of England many houses sit on generous plots, and single-storey and wraparound extensions are a natural fit.
What should I budget for a single-storey extension in Watford?
Labour and material costs vary across the UK, so for Watford we use our East of England factor (×1.06). The ranges include VAT and exclude design, structural and council fees.
Typical rates in Watford: £1,860 to £3,600 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| 3 m × 4 m 12 m² | £22,000 – £26,500 | £26,000 – £33,500 | £33,000 – £43,500 |
| 4 m × 5 m 20 m² | £37,000 – £43,500 | £43,000 – £55,500 | £55,000 – £72,500 |
| 5 m × 6 m 30 m² | £55,500 – £65,500 | £65,000 – £83,000 | £82,500 – £108,500 |
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 rear extension can usually go up to 3 m beyond the original rear wall of a semi-detached or terraced house, or 4 m on a detached house, without a planning application, provided it is no more than 4 m high, keeps eaves to 3 m within 2 m of a boundary and, with other buildings, covers no more than half the land around the original house. The larger home extension prior approval scheme raises those depths to 6 m and 8 m, with neighbours notified and a 42-day decision.
Homes in conservation areas, national parks, National Landscapes (formerly AONBs), the Broads and World Heritage Sites have tighter rules, so we always check the property's status and planning history before design starts.
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.
Building over or within 3 m of a public sewer needs the water company's consent, usually through a build-over agreement, before the foundations go in.
Applications are decided by the local planning authority (your district, borough or unitary council).
What is included
- Doors, windows, insulation, plastering and first fix to finish
- Building regulations drawings and structural calculations
- Flat or pitched roof, rooflights or lantern
- Foundations, drainage and groundworks
- Measured survey and design
Our process, step by step
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
A designer visits, takes measurements and photos, and discusses layouts, budget and timing with you.
Design and approvals
We draw the design, agree it with you and handle planning or permitted development checks and building regulations.
Fixed written price
The price is fixed in writing once the design is settled, with a clear programme and payment stages.
Build and sign-off
We build it with one project manager, book the building control inspections and hand over the completion certificate.
Common questions in Watford
Do you cover all of Watford?
Yes. We cover Watford and the surrounding parts of Hertfordshire. Site visits are free and there is no obligation.
Who do I contract with for a single-storey extension in Watford?
Your contract is with S&K Property Investments and Improvement Ltd, which designs and manages the project and the build teams who carry it out.
Do I need building regulations approval in Watford?
Yes. Almost every extension needs it, whatever the planning route. We prepare the drawings and book the inspections.
Flat roof or pitched roof?
Flat roofs give more headroom inside and suit lanterns and rooflights; pitched roofs can blend better with older houses. Both meet building regulations when built properly. See our flat roof and pitched roof pages for the details.
How much does a single-storey extension cost per square metre?
Our guide range is about £1,860 to £3,600 per m² including VAT, depending on specification. A standard-spec 4 m × 5 m room usually lands at £43,000 to £55,500 in Watford, plus design and council fees.
Book a free site visit in Watford
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.