Double-storey extensions across Harlow
Planning a double-storey extension in Harlow? We survey the house, work out the planning route, draw the design and build it, so you deal with one team from the first visit to the completion certificate.
- Guide price in HarlowFrom £40,000 inc VAT
- PlanningUsually a householder application
- Build time16–24 weeks on site
- Postcode districtsCM17, CM18, CM19, CM20
Guide prices for Harlow
Prices below are for Harlow, using the East of England factor of ×1.06. They are guide ranges including VAT for the build only, not a quote.
Typical rates in Harlow: £1,640 to £3,180 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| 3 m × 4 m, two floors 24 m² | £40,000 – £48,500 | £45,500 – £60,000 | £58,500 – £76,500 |
| 4 m × 4 m, two floors 32 m² | £52,500 – £63,000 | £61,000 – £80,000 | £78,000 – £102,000 |
| 4 m × 6 m, two floors 48 m² | £78,500 – £94,500 | £91,500 – £120,000 | £117,000 – £153,000 |
Want a range for your exact size? The guide-price tool takes about a minute.
Working in Harlow
We cover Harlow and the postcode districts CM17, CM18, CM19, CM20. We also work in nearby Waltham Abbey (8 miles), Brentwood (14 miles), Chelmsford (16 miles), Billericay (17 miles).
Hoddesdon, in Hertfordshire, is roughly 5 miles from Harlow and also on our list. 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.
Is a double-storey extension right for your house?
- Growing families who need a bedroom as well as a bigger kitchen
- Houses with enough distance to the rear or side boundary
- Homeowners who would otherwise consider moving
Planning and approvals in Harlow
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.
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.
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).
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
It starts with a visit to your house to measure, check access and talk through ideas and budget.
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
Our team builds the extension, keeps you updated weekly and finishes with building control sign-off.
Questions people ask about double-storey extensions
Who do I contract with for a double-storey extension in Harlow?
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.
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Harlow, and the guide-price tool gives a range for your own size. After the survey you get a written price before anything is agreed.
How long does a double-storey extension take to build in Harlow?
On site, typically 16 to 24 weeks once approvals are in place. Before that, allow 8–16 weeks design and approvals.
Do I need a Party Wall Agreement?
If you are in England or Wales and the work involves a shared wall or digging foundations close to a neighbour, the Party Wall etc. Act 1996 applies and notices must be served before work starts. We tell you which notices are needed.
Does a double-storey extension need planning permission?
Often, yes. In England a two-storey rear extension can be permitted development only if it projects no more than 3 m and sits at least 7 m from the rear boundary, with matching roof pitch and obscure side windows. Side extensions over one storey always need planning permission. We confirm the route at the survey.
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.