Tonbridge, Kent
Semi-detached rear extension in Tonbridge
Single or two-storey extensions for semi-detached houses, with side access and one party wall. If you live in Tonbridge and want to know what a semi-detached rear extension would cost and whether it needs planning, start with the online guide price or a free site visit.
Tonbridge sits in Kent, with postcode districts including TN9, TN10 and TN11. Where a Tonbridge 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 Tonbridge?
Guide prices for a semi-detached rear extension in Tonbridge start from our South East England rate of £2,130–£3,470 per square metre, including VAT. South East prices run above our West Midlands baseline, mainly on labour rates and clay-soil foundations.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £25,500–£41,500 |
| 4 m wide × 5 m deep (20 m²) | £42,500–£69,500 |
| 4 m wide × 6 m deep (24 m²) | £51,000–£83,500 |
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 Tonbridge?
Planning for a semi-detached rear extension in Tonbridge follows the English householder rules.
English permitted development (Class A) allows a single-storey rear extension of 3 metres on a terraced or semi-detached house and 4 metres on a detached one, measured from the original house, with a maximum height of 4 metres and eaves of no more than 3 metres within 2 metres of a boundary.
A two-storey rear extension can be permitted development in England only if it projects no more than 3 metres, stays at least 7 metres from the rear boundary, matches the existing roof pitch and has obscure-glazed upper side windows. In practice most double-storey rear extensions go through a householder planning application.
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 Tonbridge like to extend?
Tonbridge has a mix of Victorian terraces near the centre and larger Edwardian and inter-war houses further out. Clay soils across much of the South East mean deeper foundations near trees, which we plan for at the survey.
How a semi-detached rear extension in Tonbridge comes together
Look round and measure
A free visit to see the back of the house, measure it, check the drains and boundaries and hear what you need.
Options and costs
We draw layout options and price each one, so the budget shapes the design rather than surprising you later.
Approvals
Permitted development check, prior approval or planning application, then Building Regulations drawings and structural calculations, plus party wall notices where they apply.
Fixed price and build
A written price for the agreed design, a start date and a named contact through the build, ending with the building control completion certificate.
Semi-detached rear extensions near Tonbridge
Close by, we work in Royal Tunbridge Wells, about 4.3 miles away, and Sevenoaks, about 6.5 miles away.
- Semi-detached rear extension in Royal Tunbridge Wells
- Semi-detached rear extension in Sevenoaks
- Semi-detached rear extension in Crowborough
- Semi-detached rear extension in Maidstone
- Semi-detached rear extension in Snodland
Other work in Tonbridge:
FAQ
Semi-detached rear extension questions in Tonbridge
Do I need planning permission for a rear extension in Tonbridge?
Often not for a single-storey rear extension of up to 3 metres (4 metres on a detached house) under permitted development, or up to 6 or 8 metres with prior approval, unless the house is in a conservation area or its rights have been removed.
What postcode areas do you cover around Tonbridge?
Including TN9, TN10 and TN11, and the surrounding Kent area.
What if my neighbour has already extended?
That can make a matching depth easier to justify. We measure theirs at the survey.
Who will build my extension?
Vetted building teams working under contract to us. Your contract is with S&K Property Investments and Improvement Ltd for the design and the build.
How long does a rear extension take to build in Tonbridge?
Most single-storey rear extensions take 10 to 16 weeks on site and two-storey extensions 16 to 26 weeks, after design and approvals.
Do you handle building control in Tonbridge?
Yes. We apply to the council or a registered building control approver and hand over the completion certificate.