Harlow house extensions
Looking to extend your home in Harlow? Start here: extension types, guide prices for Harlow, the planning rules that apply and how a project runs.
- Postcode districtsCM17, CM18, CM19, CM20
- Price regionEast of England (×1.06)
- Planning rulesEngland
- Site visitFree, no obligation
Areas we cover around Harlow
Our survey diary covers Harlow, including CM17, CM18, CM19, CM20. Nearby, we also take on projects in Waltham Abbey (8 miles), Brentwood (14 miles), Chelmsford (16 miles), Billericay (17 miles), South Ockendon (20 miles). Hoddesdon, in Hertfordshire, is roughly 5 miles from Harlow and also on our list.
Popular extension prices in Harlow
We publish guide prices so you can budget before anyone visits. For Harlow they are adjusted by ×1.06, the factor we use across East of England.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Conservatory replacement extensions | 14 m² | £31,500 – £41,000 |
| Kitchen extensions | 20 m² | £44,500 – £56,500 |
| Side return extensions | 11 m² | £27,500 – £35,000 |
| Wraparound extensions | 25 m² | £60,500 – £77,000 |
| Orangery extensions | 16 m² | £47,000 – £59,500 |
| Extensions over a garage | 12 m² | £26,500 – £34,500 |
| Single-storey rear extensions | 20 m² | £43,000 – £55,500 |
Choosing the right extension in Harlow
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, wraparound extensions, bungalow extensions or double-storey extensions gives the most useful space for the budget.
Planning and building control in Harlow
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).
All extension types we build in Harlow
- Extension plans and drawings · from £1,250
- Annexe extensions · from £58,000
- Double-storey extensions · from £40,000
- Side extensions · from £23,000
- Wraparound extensions · from £38,000
- Extensions over a garage · from £25,000
- Utility and boot room extensions · from £14,500
- Kitchen extensions · from £28,500
- Planning permission for extensions · from £350
- Bungalow extensions · from £27,500
- Pitched roof extensions · from £23,500
- Conservatory replacement extensions · from £21,000
- Glass box extensions · from £31,500
- Timber frame extensions · from £22,000
- Flat roof extensions · from £22,000
- Bedroom extensions · from £27,500
- Home office extensions · from £16,500
- Porch extensions · from £4,200
- Orangery extensions · from £31,500
- Building regulations for extensions · from £950
- Side return extensions · from £19,000
- Single-storey rear extensions · from £22,000
Free site visit
It starts with a visit to your house to measure, check access and talk through ideas and budget.
Design and approvals
We produce the drawings and structural design, and manage the approvals so they are in place before work starts.
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
The build is managed from start to finish, inspected at each stage and signed off on completion.
Questions about extensions in Harlow
How much does an extension cost in Harlow?
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 I need planning permission for an extension in Harlow?
Not always. It depends on the size, position and your property's history. Many single-storey rear extensions in England are permitted development or can use prior approval.
Do you cover all of Harlow?
Yes, including the surrounding parts of Essex. 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.
Can I get a price before anyone visits?
Yes. This page shows guide prices adjusted for Harlow, and the guide-price tool gives a range for your own size and finish in about a minute.
Book a free site visit in Harlow
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.