St Helens house extensions
More space without moving: we plan and build extensions across St Helens, with one team for the drawings, the council and the build.
- Postcode districtsL34, L35, WA9, WA10, WA11, WA12
- Price regionNorth West England (×0.95)
- Planning rulesEngland
- Site visitFree, no obligation
Which extension suits a St Helens home?
Across the North West, terraced houses with small rear yards suit compact rear and side return extensions, while suburban semis have room for more.
The types we would usually look at first for a home in St Helens are double-storey extensions, side return extensions and single-storey rear extensions, depending on the garden and how the house is laid out.
Covering St Helens and nearby
Our survey diary covers St Helens, including L34, L35, WA9, WA10, WA11, WA12. Nearby, we also take on projects in Prescot (3 miles), Huyton (5 miles), Newton-le-Willows (5 miles), Golborne (6 miles), Kirkby (7 miles). For homes towards Greater Manchester, Ashton-in-Makerfield is around 4 miles away.
Guide prices for St Helens
Every figure below is a guide for St Helens, adjusted for North West England 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) |
|---|---|---|
| Conservatory replacement extensions | 14 m² | £28,500 – £37,000 |
| Kitchen extensions | 20 m² | £39,500 – £50,500 |
| Orangery extensions | 16 m² | £42,500 – £53,500 |
| Double-storey extensions | 32 m² | £54,500 – £71,500 |
| Extensions over a garage | 12 m² | £23,500 – £31,000 |
Planning rules in St Helens
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).
Every extension type in St Helens
- Flat roof extensions · from £19,500
- Double-storey extensions · from £36,000
- Porch extensions · from £3,800
- Extension plans and drawings · from £1,100
- Glass box extensions · from £28,500
- Side return extensions · from £17,000
- Annexe extensions · from £52,000
- Planning permission for extensions · from £300
- Bungalow extensions · from £24,500
- Side extensions · from £20,500
- Pitched roof extensions · from £21,000
- Timber frame extensions · from £19,500
- Bedroom extensions · from £24,500
- Home office extensions · from £15,000
- Extensions over a garage · from £22,500
- Kitchen extensions · from £25,500
- Conservatory replacement extensions · from £19,000
- Utility and boot room extensions · from £13,000
- Orangery extensions · from £28,500
- Single-storey rear extensions · from £19,500
- Building regulations for extensions · from £850
- Wraparound extensions · from £34,000
Free site visit
It starts with a visit to your house to measure, check access and talk through ideas and budget.
Design and approvals
Drawings are prepared and agreed with you, then submitted for the right planning route and building regulations approval.
Fixed written price
We confirm the build price in writing, based on the approved drawings and the finishes you have chosen.
Build and sign-off
Our team builds the extension, keeps you updated weekly and finishes with building control sign-off.
Questions about extensions in St Helens
How much does an extension cost in St Helens?
Using our North West England 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.
Who do I contract with?
Your contract is with S&K Property Investments and Improvement Ltd, which designs and manages the project and the build teams who carry it out.
Do you cover all of St Helens?
Yes, including the surrounding parts of Merseyside. Site visits are free and there is no obligation.
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.
Book a free site visit in St Helens
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.