Harwich, Essex
Semi-detached rear extension in Harwich
We plan and build rear extensions for semi-detached houses for homeowners in Harwich. Single or two-storey extensions for semi-detached houses, with side access and one party wall. Start with a free site visit, then a written price once the design is agreed.
Harwich and its postcode districts CO12 are part of our Essex coverage. Where a Harwich semi already has a small lean-to at the back, we usually replace it rather than extend it.
Book a free site visit
Tell us about the house and we'll call to arrange a free, no-obligation visit.
How much does a semi-detached rear extension cost in Harwich?
Guide prices for a semi-detached rear extension in Harwich start from our East of England rate of £2,010–£3,290 per square metre, including VAT. East of England prices run slightly above our West Midlands baseline; clay soils near trees are the main foundation variable.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £24,000–£39,500 |
| 4 m wide × 5 m deep (20 m²) | £40,500–£65,500 |
| 4 m wide × 6 m deep (24 m²) | £48,500–£79,000 |
We put a fixed price in writing once the design is agreed, and explain any provisional sums such as foundations.
Do you need planning permission for a semi-detached rear extension in Harwich?
The planning route for a semi-detached rear extension in Harwich is set by England's householder rules and your council.
Under England's householder permitted development rules you can usually add 3 metres at the back of an attached house, or 4 metres on a detached house, without a planning application, as long as the extension stays under 4 metres high and its eaves stay under 3 metres where it is within 2 metres of a boundary.
England's rules allow a rear extension of more than one storey without an application only when it is no deeper than 3 metres and at least 7 metres from the boundary opposite the rear wall, and never on designated land. Most two-storey schemes need householder planning permission.
England also has the larger home extension route: a single-storey rear extension of up to 6 metres on an attached house or 8 metres on a detached house, after prior approval from the council. The council notifies your neighbours and has 42 days to decide; the fee is £249 (£310 for applications made from 8 December 2026). The route is not available on designated land such as conservation areas.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent. At the first visit we measure what is there now and tell you which route fits: permitted development, prior approval or a planning application.
What are homes in Harwich like to extend?
Harwich mixes Victorian terraces with 1930s semis, so both side returns and full-width kitchen extensions suit houses here.
How a semi-detached rear extension in Harwich comes together
Free site visit
We measure the house and garden, look at the back wall, drainage and boundaries, and talk through what you want from the space.
Options and costs
We draw layout options and price each one, so the budget shapes the design rather than surprising you later.
Planning and regulations
We take the design through the right planning route, then produce the construction drawings and engineer's calculations for building control.
Build and sign-off
We build to the approved drawings with regular updates, then hand over the building control completion certificate and any guarantees from suppliers.
Semi-detached rear extensions near Harwich
Neighbouring places we cover include Felixstowe (3.2 miles) and Walton-on-the-Naze (6.5 miles).
- Semi-detached rear extension in Felixstowe
- Semi-detached rear extension in Walton-on-the-Naze
- Semi-detached rear extension in Frinton-on-Sea
- Semi-detached rear extension in Kesgrave
- Semi-detached rear extension in Ipswich
Other work in Harwich:
FAQ
Semi-detached rear extension questions in Harwich
Do I need a party wall agreement?
In England, usually yes if the extension is on or near a shared boundary or the foundations are close to a neighbour's building. We serve the notices.
Can I live at home while the extension is built?
Usually yes. Most of the work is outside until the back wall is opened near the end, and that stage is screened off.
How long does a semi extension take?
10 to 16 weeks on site for a single-storey extension.
Can I get a price without a visit?
Our online guide-price tool gives a range in a couple of minutes. A written price needs a survey.
Do you handle building control in Harwich?
Yes. We apply to the council or a registered building control approver and hand over the completion certificate.
Can you match the brick or stone on my Harwich house?
We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.