Extending your home in Grantham
Planning an extension in Grantham? Compare extension types, see guide prices adjusted for Grantham and book a free site visit.
- Postcode districtsNG31, NG32
- Price regionEast Midlands (×0.95)
- Planning rulesEngland
- Site visitFree, no obligation
Planning rules in Grantham
In England a single-storey rear extension can usually go up to 3 m beyond the original rear wall of a semi-detached or terraced house, or 4 m on a detached house, without a planning application, provided it is no more than 4 m high, keeps eaves to 3 m within 2 m of a boundary and, with other buildings, covers no more than half the land around the original house. The larger home extension prior approval scheme raises those depths to 6 m and 8 m, with neighbours notified and a 42-day decision.
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.
In a conservation area, national park, National Landscape, the Broads or a World Heritage Site the permitted development limits are tighter (no side or two-storey extensions without an application). Listed homes need listed building consent, and if permitted development rights have been removed, any extension needs an application.
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.
Applications are decided by the local planning authority (your district, borough or unitary council).
Guide prices for Grantham
Every figure below is a guide for Grantham, adjusted for East Midlands build costs (×0.95) and including VAT. Design and council fees are shown separately on each page.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Double-storey extensions | 32 m² | £54,500 – £71,500 |
| Wraparound extensions | 25 m² | £54,500 – £69,000 |
| Extensions over a garage | 12 m² | £23,500 – £31,000 |
| Single-storey rear extensions | 20 m² | £38,500 – £49,500 |
| Conservatory replacement extensions | 14 m² | £28,500 – £37,000 |
| Side return extensions | 11 m² | £25,000 – £31,500 |
Where we work near Grantham
Our survey diary covers Grantham, including NG31, NG32. The same team covers Stamford (19 miles), Spalding (22 miles), Lincoln (22 miles), Boston (26 miles), Gainsborough (33 miles), all within easy reach. For homes towards Nottinghamshire, Newark-on-Trent is around 13 miles away.
Choosing the right extension in Grantham
The East Midlands has plenty of inter-war and post-war semis and detached houses with room to extend, alongside Victorian terraces in the towns.
Start by comparing conservatory replacement extensions, double-storey extensions and side extensions: between them they cover most of the layouts we see requested for houses like these.
All extension types we build in Grantham
- Planning permission for extensions · from £300
- Annexe extensions · from £52,000
- Bungalow extensions · from £24,500
- Extensions over a garage · from £22,500
- Porch extensions · from £3,800
- Single-storey rear extensions · from £19,500
- Building regulations for extensions · from £850
- Orangery extensions · from £28,500
- Glass box extensions · from £28,500
- Bedroom extensions · from £24,500
- Conservatory replacement extensions · from £19,000
- Pitched roof extensions · from £21,000
- Flat roof extensions · from £19,500
- Extension plans and drawings · from £1,100
- Kitchen extensions · from £25,500
- Side return extensions · from £17,000
- Side extensions · from £20,500
- Double-storey extensions · from £36,000
- Utility and boot room extensions · from £13,000
- Home office extensions · from £15,000
- Wraparound extensions · from £34,000
- Timber frame extensions · from £19,500
Free site visit
A designer visits, takes measurements and photos, and discusses layouts, budget and timing with you.
Design and approvals
We produce the drawings and structural design, and manage the approvals so they are in place before work starts.
Fixed written price
You receive a written, itemised price and programme. Nothing starts until you are happy with it.
Build and sign-off
We build it with one project manager, book the building control inspections and hand over the completion certificate.
Questions about extensions in Grantham
How much does an extension cost in Grantham?
Using our East Midlands factor (×0.95), a standard-spec single-storey extension of 20 m² is a guide £38,500 to £49,500 including VAT, and a 32 m² two-storey extension £54,500 to £71,500. Your written price follows the survey.
Can I get a price before anyone visits?
Yes. This page shows guide prices adjusted for Grantham, and the guide-price tool gives a range for your own size and finish in about a minute.
Do you handle building regulations?
Yes. We prepare the drawings and calculations, submit them and book inspections, ending with a completion certificate.
Will my neighbours need to be told?
If you apply for planning or prior approval the council notifies them, and in England party wall notices may be needed for work near a shared boundary.
Do I need planning permission for an extension in Grantham?
Not always. It depends on the size, position and your property's history. Many single-storey rear extensions in England are permitted development or can use prior approval.
Book a free site visit in Grantham
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.