What is a double-storey extension?
A double-storey extension (also called a two-storey extension) adds rooms on both the ground and first floor in one build. It typically gives a larger kitchen or living space downstairs and an extra bedroom or bathroom above.
How much does a double-storey extension cost in Twickenham?
In Twickenham, a double-storey extension typically costs £2,150–£3,250 per m² of floor area (both floors), including VAT at 20% (standard rate). For a typical 36 m² project that is roughly £77,500–£117,000. Building costs in London run about 30% above the UK average, and the figures for Twickenham are adjusted to reflect that. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (25 m²) | £54,000–£81,000 |
| Typical project (36 m²) | £77,500–£117,000 |
| Larger project (50 m²) | £107,500–£162,500 |
| Rate per m² | £2,150–£3,250 |
The main things that change the cost:
- Total floor area across both floors
- Roof design and how it joins the existing roof
- Scaffolding and access to the rear
- Brick matching and external finishes
Use the guide price tool to see how size and specification change the figure, then ask for a written, itemised quote.
Do you need planning permission for a double-storey extension in Twickenham?
Before anything is built in Twickenham, we confirm which approvals apply in England. In England an extension of more than one storey can only be permitted development at the rear, no more than 3 metres deep and at least 7 metres from the rear boundary, with matching materials and any upper side windows obscure-glazed. Most double-storey extensions therefore go through a householder planning application.
Where work involves a shared wall, building on the boundary, or digging foundations within 3 metres of a neighbour’s building and deeper than its foundations (or within 6 metres for deeper work), the Party Wall etc. Act 1996 applies and notices must be served before work starts.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
The work we manage on a double-storey extension:
- Brick or block walls, floors and a roof tied into the house
- Opening up at both levels with steel beams
- Windows, doors and staircase alterations
- Building control sign-off
- Structural engineer’s calculations
- Foundations, drainage and scaffolding
How long does it take?
The build itself usually takes 14 to 20 weeks on site, after planning and building control approval. Allow time beforehand for drawings and approvals, usually 3 to 4 months.
Building in Twickenham
Many London boroughs have conservation areas and detailed design guides, so early design advice saves time at the planning stage.
We work across Twickenham and neighbouring areas such as Teddington, Richmond and Kingston upon Thames. Postcodes we cover in Twickenham include TW1 and TW2.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Design and pricing
Design options, then a fixed quote based on the chosen drawings and specification.
- 03
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about double-storey extensions in Twickenham
Can I live at home during the work?
Most families stay put. The shell is built first and the house is opened up late in the job, so disruption inside is limited to a few weeks.
How long does a double-storey extension take in Twickenham?
Typically 14 to 20 weeks on site, after planning and building control approval. Design and approvals beforehand usually take 3 to 4 months.
How close can it be to my neighbour?
Councils look at loss of light and outlook for neighbours. Many apply a 45-degree guideline from the nearest neighbouring window. We design to the council’s published guidance to give the application the best chance.
How much does a double-storey extension cost in Twickenham?
In Twickenham, a double-storey extension typically costs £2,150–£3,250 per m² of floor area (both floors), including VAT at 20% (standard rate). A typical 36 m² project comes to roughly £77,500–£117,000. Your fixed price depends on the survey and drawings.
Does a double-storey extension need planning permission?
Usually. In England a two-storey rear extension can only be permitted development if it is no more than 3 metres deep and at least 7 metres from the rear boundary, and side extensions over one storey always need permission. In practice most are approved through a planning application.