House extensions in Watford
Planning an extension in Watford? Compare extension types, see guide prices adjusted for Watford and book a free site visit.
- Postcode districtsWD1, WD2, WD17, WD18, WD23, WD24
- Price regionEast of England (×1.06)
- Planning rulesEngland
- Site visitFree, no obligation
Which extension suits a Watford home?
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.
For many houses here, bungalow extensions, wraparound extensions or single-storey rear extensions gives the most useful space for the budget.
Popular extension prices in Watford
We publish guide prices so you can budget before anyone visits. For Watford they are adjusted by ×1.06, the factor we use across East of England.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Orangery extensions | 16 m² | £47,000 – £59,500 |
| Extensions over a garage | 12 m² | £26,500 – £34,500 |
| Wraparound extensions | 25 m² | £60,500 – £77,000 |
| Kitchen extensions | 20 m² | £44,500 – £56,500 |
| Conservatory replacement extensions | 14 m² | £31,500 – £41,000 |
| Double-storey extensions | 32 m² | £61,000 – £80,000 |
| Single-storey rear extensions | 20 m² | £43,000 – £55,500 |
Where we work near Watford
We cover Watford and the postcode districts WD1, WD2, WD17, WD18, WD23, WD24. Neighbouring towns we cover include Bushey (2 miles), Rickmansworth (4 miles), Borehamwood (5 miles), St Albans (7 miles), Hemel Hempstead (7 miles). For homes towards Greater London, Pinner is around 4 miles away.
Do extensions in Watford need planning permission?
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.
In England a two-storey rear extension is permitted development only if it projects no more than 3 m from the original rear wall, sits at least 7 m from the rear boundary, matches the roof pitch and uses obscure, non-opening side windows upstairs. Most two-storey extensions therefore go through a householder planning application, which costs £548 from 1 April 2026 and normally takes about 8 weeks.
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.
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).
Every extension type in Watford
- Extensions over a garage · from £25,000
- Pitched roof extensions · from £23,500
- Flat roof extensions · from £22,000
- Bungalow extensions · from £27,500
- Conservatory replacement extensions · from £21,000
- Bedroom extensions · from £27,500
- Glass box extensions · from £31,500
- Double-storey extensions · from £40,000
- Utility and boot room extensions · from £14,500
- Orangery extensions · from £31,500
- Annexe extensions · from £58,000
- Wraparound extensions · from £38,000
- Home office extensions · from £16,500
- Porch extensions · from £4,200
- Kitchen extensions · from £28,500
- Single-storey rear extensions · from £22,000
- Side extensions · from £23,000
- Timber frame extensions · from £22,000
- Planning permission for extensions · from £350
- Building regulations for extensions · from £950
- Side return extensions · from £19,000
- Extension plans and drawings · from £1,250
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
We confirm the build price in writing, based on the approved drawings and the finishes you have chosen.
Build and sign-off
Our team builds the extension, keeps you updated weekly and finishes with building control sign-off.
Questions about extensions in Watford
How much does an extension cost in Watford?
Using our East of England factor (×1.06), a standard-spec single-storey extension of 20 m² is a guide £43,000 to £55,500 including VAT, and a 32 m² two-storey extension £61,000 to £80,000. Your written price follows the survey.
Do you handle building regulations?
Yes. We prepare the drawings and calculations, submit them and book inspections, ending with a completion certificate.
Can I get a price before anyone visits?
Yes. This page shows guide prices adjusted for Watford, and the guide-price tool gives a range for your own size and finish in about a minute.
Do you cover all of Watford?
Yes, including the surrounding parts of Hertfordshire. Site visits are free and there is no obligation.
Will my neighbours need to be told?
If you apply for planning or prior approval the council notifies them, and in England party wall notices may be needed for work near a shared boundary.
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.