Longfield, Kent
Semi-detached rear extension in Longfield
Single or two-storey extensions for semi-detached houses, with side access and one party wall. If you live in Longfield 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.
We cover Longfield (DA3, DA4 and DA13) as part of our Kent work. In Longfield we measure the attached neighbour's extension at the survey, because it often sets the sensible depth for yours.
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 Longfield?
A semi-detached rear extension in Longfield is priced at £2,130–£3,470 per square metre including VAT as a guide, before kitchen fit-out and fees. 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 |
Your written price follows a measured survey and an agreed design, so it reflects your house, not an average.
Do you need planning permission for a semi-detached rear extension in Longfield?
Whether your semi-detached rear extension in Longfield needs a planning application depends on its size, your house and any local restrictions.
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. Before any drawing we look up the property's history with the council, because earlier extensions and removed rights change the answer.
What are homes in Longfield like to extend?
Commuter semis and detached houses make up much of Longfield, and longer gardens make England's prior approval route for deeper rear extensions worth considering. Semi-detached houses are common across Kent, and their side access makes rear extensions quicker to build.
How a semi-detached rear extension in Longfield comes together
Survey visit
We visit free of charge, measure up, check access, drainage and neighbours' extensions, and note what you want the room to do.
Drawings and budget
Floor plans and elevations for the options, each with a guide price.
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 Longfield
From Longfield, the nearest places we also cover are Hartley (0.7 miles) and Swanscombe (3.5 miles).
- Semi-detached rear extension in Hartley
- Semi-detached rear extension in Swanscombe
- Semi-detached rear extension in Gravesend
- Semi-detached rear extension in Dartford
- Semi-detached rear extension in Tilbury
Other work in Longfield:
FAQ
Semi-detached rear extension questions in Longfield
Will I need a structural engineer?
Yes for the beam over the new opening and usually the foundations; we arrange them and their calculations go to building control.
How much does a semi-detached rear extension cost in Longfield?
As a guide, £2,130–£3,470 per square metre including VAT for a standard specification. For example, 3 m wide × 4 m deep (12 m²): about £25,500–£41,500 at that rate. Your written price follows the survey.
What if my neighbour has already extended?
That can make a matching depth easier to justify. We measure theirs at the survey.
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.
Can you match the brick or stone on my Longfield house?
We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.
Is the site visit in Longfield free?
Yes. We visit, measure up and talk through the options with no cost and no obligation.