First-floor extensions in Tolworth
Thinking about a first-floor extension in Tolworth? We design it, take it through the approvals it needs and build it, with one team responsible from the first visit to the final certificate.
What we'd confirm first for a project in Tolworth.
- Postcode districts
- KT5
- County / area
- Greater London, England
- Price region
- London
- Guide price
- £30,000–£43,500 (£2,160–£3,120 per m²)
- Approval route
- It may be permitted development if it goes no more than 3 m beyond the original rear wall (counting any single-storey part) and stays 7 m from the rear boundary; otherwise it needs planning permission.
- Nearest towns
- Surbiton (1.1 miles), Hook (1.4 miles), Chessington (1.6 miles)
- First visit
- Free, no obligation
About a first-floor extension
A first-floor extension suits you if your house already has a single-storey extension and you need more space upstairs. You get a structural check of the existing walls and foundations, a design that ties the new floor into the house, the approvals your nation needs, building regulations approval and the build, managed by us and carried out by vetted teams working under S&K.
We cover postcode district KT5 in and around Tolworth, along with neighbouring Surbiton, Hook and Chessington.
What it costs in Tolworth
Most of the cost of a first-floor extension is set by its size and specification. For Tolworth and the rest of London, our guide is £2,160–£3,120 per m² including VAT, so about £30,000–£43,500 for 4 m × 3.5 m of new first-floor space (14 m²). Keep a contingency of around 10% for things nobody can see until the ground is opened up.
| Spec | Per m² | 4 m × 3.5 m of new first-floor space (14 m²) |
|---|---|---|
| Essential | £1,990–£2,870 per m² | £28,000–£40,000 |
| Standard | £2,160–£3,120 per m² | £30,000–£43,500 |
| Premium | £2,590–£3,740 per m² | £36,500–£52,500 |
Planning and building regulations in Tolworth
In England, adding a first floor turns a single-storey extension into one of more than one storey. To be permitted development, the extension as a whole must go no more than 3 m beyond the rear wall of the original house and stay at least 7 m from the rear boundary, with matching materials and roof pitch. Over a side extension it always needs planning permission, costing £548 (or £575 for applications made from 8 December 2026).
Approval in England: Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.
Building regulations: Building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end.
Design points for Tolworth homes
Replacing the flat roof
The existing roof usually comes off and is replaced by a new first-floor structure. The room below is exposed for a short time, so we plan temporary weatherproofing and sequence the work to keep the kitchen or living room usable for as long as possible.
Escape and fire safety
A new first-floor bedroom needs an escape window with a clear opening of at least 0.33 m², at least 450 mm wide and 450 mm high, with the bottom no more than 1,100 mm above the floor, unless there is a protected route to the stairs.
How we'd run your project
Free site visit
We visit your home in Tolworth, look at the structure, access and boundaries, and talk through what you want the new rooms to do.
Plans, then approval
Measured survey, design, then the right approval route for your house. We explain each step before we take it.
Technical design
We prepare the building regulations drawings, structural calculations and specification so the build price can be fixed.
Build and sign-off
Vetted teams working under S&K build the extension, and we arrange the building control completion certificate at the end.
Questions about first-floor extensions in Tolworth
Which postcodes do you cover around Tolworth?
We cover Tolworth (KT5) and nearby places including Surbiton, Hook and Chessington, plus the rest of Greater London. The first site visit is free.
How long does a first-floor extension take?
Allow 4 to 8 weeks for survey and design, then the approval period (councils should decide householder applications within 8 weeks of validation), then 4 to 8 weeks of technical design, which can overlap. The build itself usually takes 14 to 20 weeks, longer for large or complex designs.
Do I need planning permission for a first-floor extension in Tolworth?
Tolworth is in England, so England planning rules apply. It may be permitted development if it goes no more than 3 m beyond the original rear wall (counting any single-storey part) and stays 7 m from the rear boundary; otherwise it needs planning permission. If in doubt, a lawful development certificate or a planning application gives you certainty before you build.
What happens to the room below while the first floor is built?
The old roof is removed, so the room below is exposed for a short period. We fit temporary weather protection, plan the work so the roof comes off only when the new structure is ready, and agree with you which rooms will be out of use and for roughly how long.
Will the first-floor extension match my house?
It should, and in England matching materials and roof pitch is a condition of permitted development. We match brick, tile, mortar colour and window style where we can, and tell you at the design stage if an exact brick match is not available, so you can choose between the closest match and render or cladding.
Nearby
Nearby towns we cover for first-floor extensions:
Other extensions in Tolworth
- Rear
- Side
- Wraparound
- Part two-storey
- Over a garage
- Semi-detached
- Detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in Tolworth · First-floor extensions across Greater London
The quickest next step is a visit. We'll look at your house in Tolworth and give you an honest view of the options.