Brentwood double-storey extensions, designed and built
Brentwood homeowners can use us for the whole double-storey extension project: survey, design, planning or permitted development checks, building regulations and the build itself.
- Guide price in BrentwoodFrom £40,000 inc VAT
- PlanningUsually a householder application
- Build time16–24 weeks on site
- Postcode districtsCM13, CM14, CM15
Double-storey extension prices in Brentwood
For Brentwood we adjust our national guide rates by ×1.06, the factor we use for East of England. Figures include VAT; your written quote after the survey replaces them.
Typical rates in Brentwood: £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 |
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 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.
Before any drawing is finalised we check whether the house is listed, in a conservation area or subject to an Article 4 direction.
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
- Ground and first floor structure, roof tied into the existing roof
- Householder planning application where needed
- Foundations sized for two floors
- Insulation, plastering, electrics and plumbing to finish
- Measured survey, design and planning drawings
Local to Brentwood
Across CM13, CM14, CM15, we can visit, measure and advise. We also work in nearby Billericay (5 miles), Basildon (7 miles), South Ockendon (8 miles), Stanford-le-Hope (9 miles).
For homes towards Greater London, Hornchurch is around 6 miles away. Across the East of England many houses sit on generous plots, and single-storey and wraparound extensions are a natural fit.
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
We visit your Brentwood home, measure up, talk through what you want and check the planning position.
Design and approvals
We draw the design, agree it with you and handle planning or permitted development checks and building regulations.
Fixed written price
With the design and specification agreed, you get a fixed written price and a start date.
Build and sign-off
Work is carried out to the agreed programme, inspected by building control and signed off at the end.
Your questions about a double-storey extension in Brentwood
Will my neighbours in Brentwood 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.
How long does a double-storey extension take to build in Brentwood?
On site, typically 16 to 24 weeks once approvals are in place. Before that, allow 8–16 weeks design and approvals.
Who do I contract with for a double-storey extension in Brentwood?
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.
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.
Is a two-storey extension cheaper per square metre?
Usually. Our guide range is about £1,640 to £3,180 per m² of new floor area including VAT, compared with £1,860 to £3,600 per m² for single-storey work, because the foundations and roof are shared across two floors.
Book a free site visit in Brentwood
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.