Boston, Lincolnshire
Semi-detached rear extension in Boston
Single or two-storey extensions for semi-detached houses, with side access and one party wall. We design, get the approvals for and build rear extensions for semi-detached houses in Boston and the surrounding area, with one contract from the first survey to building control sign-off.
We cover Boston (PE21) as part of our Lincolnshire work. Where a Boston 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 Boston?
In Boston, our guide for a semi-detached rear extension is £1,840–£3,010 per square metre including VAT for a standard specification. East Midlands prices sit a little below our West Midlands baseline.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £22,000–£36,000 |
| 4 m wide × 5 m deep (20 m²) | £37,000–£60,000 |
| 4 m wide × 6 m deep (24 m²) | £44,000–£72,000 |
Ground conditions, glazing, the roof and how far the house is opened up move the final figure within the range.
Do you need planning permission for a semi-detached rear extension in Boston?
The planning route for a semi-detached rear extension in Boston is set by England's householder rules and your council.
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.
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.
If 3 or 4 metres is not enough, England's prior approval route allows 6 metres on a terraced or semi-detached house and 8 metres on a detached house for a single-storey rear extension. Neighbours are consulted, the council decides within 42 days, and the fee is £249, rising to £310 from 8 December 2026.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent. We check your house's planning history and any conservation area before drawing, so the route is clear before you spend on plans.
What are homes in Boston like to extend?
Boston has plenty of inter-war semis and bungalows, and single-storey rear extensions suit both.
How a semi-detached rear extension in Boston 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.
Approvals
Permitted development check, prior approval or planning application, then Building Regulations drawings and structural calculations, plus party wall notices where they apply.
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 Boston
From Boston, the nearest places we also cover are Spalding (14.1 miles) and Sleaford (16.0 miles).
- Semi-detached rear extension in Spalding
- Semi-detached rear extension in Sleaford
- Semi-detached rear extension in Skegness
- Semi-detached rear extension in Bourne
- Semi-detached rear extension in Wisbech
Other work in Boston:
FAQ
Semi-detached rear extension questions in Boston
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 much does a semi-detached rear extension cost in Boston?
As a guide, £1,840–£3,010 per square metre including VAT for a standard specification. For example, 3 m wide × 4 m deep (12 m²): about £22,000–£36,000 at that rate. Your written price follows the survey.
How long does a semi extension take?
10 to 16 weeks on site for a single-storey extension.
How long does a rear extension take to build in Boston?
Most single-storey rear extensions take 10 to 16 weeks on site and two-storey extensions 16 to 26 weeks, after design and approvals.
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 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.