Part single, part two-storey extensions in Cranford

Quick reference for homeowners in Cranford.

Postcode districts: TW6
County / area: Greater London, England
Price region: London
Guide price: £86,500–£119,000 (£2,400–£3,300 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: Heston (1.7 miles), Feltham (2.1 miles), Hounslow (2.3 miles)
First visit: Free, no obligation

About a part single, part two-storey extension

A part single, part two-storey extension is an extension where the ground floor is wider or deeper than the floor above, so only part of it rises to two storeys. It usually gives a large kitchen or living area with roof lights below and one bedroom or bathroom above. It is often a good way to add space while limiting the effect on neighbours.

Around Cranford we also work in Heston, Feltham and Hounslow, and across the rest of Greater London. Postcode district in and near Cranford: TW6.

What it costs in Cranford

For budgeting in Cranford, allow around £86,500–£119,000 for a part single, part two-storey extension with a 6 m × 4 m ground floor and a first floor over half of it (36 m² in total). That's based on £2,400–£3,300 per m² including VAT for London. Design fees, structural calculations and approval fees are separate and listed on our prices page.

Spec	Per m²	A 6 m × 4 m ground floor and a first floor over half of it (36 m² in total)
Essential	£2,210–£3,040 per m²	£79,500–£109,500
Standard	£2,400–£3,300 per m²	£86,500–£119,000
Premium	£2,880–£3,960 per m²	£103,500–£142,500

Planning and building regulations in Cranford

In England, the extension can only be permitted development if it goes no more than 3 m beyond the original rear wall and stays at least 7 m from the rear boundary, with matching materials and roof pitch. We check the whole design against the rules, including the 50% garden coverage limit. If any part fails, or extends beyond a side wall on two floors, you need 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 Cranford homes

Structure at the step

The first-floor wall above often sits over the new open-plan space, so it needs a steel beam or frame to carry it. Loads come down at different points than in a full two-storey design, and the engineer sizes the foundations to suit each part.

Where to put the two-storey part

The two-storey section usually works best away from the closest neighbour, with the single-storey part on that boundary side. We test a few positions against neighbours' windows, the upstairs layout and the roof shape before choosing the one to take forward.

How we'd run your project

Free site visit
We visit your home in Cranford, 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.
Fixed price in writing
With approved drawings and calculations, we give you a fixed build price and a programme you can plan around.
Build
Foundations, walls, floor, roof, windows, then first and second fix. We break through into the house as late as we can.

Questions about part single, part two-storey extensions in Cranford

Do I need planning permission for a part single, part two-storey extension in Cranford?

Cranford 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.

How long does a part single, part two-storey 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.

Which postcodes do you cover around Cranford?

We cover Cranford (TW6) and nearby places including Heston, Feltham and Hounslow, plus the rest of Greater London. The first site visit is free.

Which side should the two-storey part go on?

Usually the side furthest from the nearest neighbour's windows, so the single-storey part sits nearest them and keeps their light. Other factors are where the stairs land upstairs, which room needs the extra space and where drains run. We sketch options at the design stage and explain which is most likely to be approved.

Can I add roof lights to the single-storey part?

Yes. Roof lights or a lantern over the single-storey part are one of the main reasons to choose this design, as they light the middle of a deep kitchen. In England they count towards the Part L glazing allowance, normally 25% of the new floor area plus windows removed, so we balance them with the rear doors.

Nearby

Close to Cranford? We work across the area, including:

Other extensions in Cranford

All two-storey extension services in Cranford · Part single, part two-storey extensions across Greater London

Tell us about your house in Cranford and we'll call you back to arrange a free, no-obligation visit.