Two-storey extensions for semi-detached houses in St Ives

St Ives: the key facts for this kind of project.

Postcode districts: CB24 and PE27
County / area: Cambridgeshire, England
Price region: East of England
Guide price: £57,500–£78,000 (£2,060–£2,780 per m²)
Approval route: Depends on position: a two-storey rear extension may be permitted development (3 m deep, 7 m from the rear boundary); a two-storey side extension needs planning permission.
Nearest towns: Huntingdon (4.6 miles), Chatteris (10.1 miles), St Neots (11.3 miles)
Distance to Peterborough: about 18.2 miles
First visit: Free, no obligation

About a two-storey extension for a semi-detached house

A two-storey extension for a semi-detached house is a two-floor addition to the rear, the open side, or both, designed around the attached neighbour on one side. The rear is often the simplest option and can sometimes be permitted development, while a side extension uses the gap on the detached side. Both need care with the shared party wall and the neighbour's light.

We cover St Ives (CB24 and PE27) and the places around it, including Huntingdon (4.6 miles), Chatteris (10.1 miles) and St Neots.

What it costs in St Ives

Expect a two-storey extension for a semi-detached house in St Ives to land somewhere around £57,500–£78,000 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). Our East of England guide rate is £2,060–£2,780 per m², including VAT. Steelwork for wide openings is the item most likely to move the figure; we'll know once the engineer has designed it.

Spec	Per m²	A 4 m × 3.5 m footprint on two floors (28 m² of new floor space)
Essential	£1,900–£2,560 per m²	£53,000–£71,500
Standard	£2,060–£2,780 per m²	£57,500–£78,000
Premium	£2,470–£3,340 per m²	£69,000–£93,500

Planning and building regulations in St Ives

In England, a two-storey rear extension on a semi can be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary, with matching materials and roof pitch. A two-storey side or wraparound extension always needs planning permission, costing £548 (or £575 for applications made from 8 December 2026). Protected areas such as conservation areas exclude two-storey rear permitted development.

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 St Ives homes

Rear, side or both

On a semi, a rear extension sits against the attached neighbour, while a side extension faces the detached neighbour and the street. We compare the space, cost and approval route for each, and for a wraparound, before you commit to one design.

Keeping the pair balanced

Semis are designed as matching pairs, and a side extension changes that balance. Setting the side extension back from the front wall and keeping its ridge lower helps the pair still read as a pair, which councils' design guides commonly ask for.

How we'd run your project

Start at your house
We come to your home in St Ives, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
Drawings and permission
Our designers produce plans and elevations, then we take care of planning or permitted development checks with the council covering St Ives.
Price it properly
Once the engineer's calculations are in, we fix the build price in writing, with a clear list of what's included.
Build and hand over
We manage the build from groundworks to decoration-ready finish and hand over with the completion paperwork.

Questions about two-storey extensions for semi-detached houses in St Ives

Do I need planning permission for a two-storey extension for a semi-detached house in St Ives?

St Ives is in England, so England planning rules apply. Depends on position: a two-storey rear extension may be permitted development (3 m deep, 7 m from the rear boundary); a two-storey side extension needs planning permission. If in doubt, a lawful development certificate or a planning application gives you certainty before you build.

Who handles building regulations for a project in St Ives?

We handle it as part of the project. What's needed in England: building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end. We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.

Which postcodes do you cover around St Ives?

We cover St Ives (CB24 and PE27) and nearby places including Huntingdon, Chatteris and St Neots, plus the rest of Cambridgeshire. The first site visit is free.

Does a two-storey extension add value to a semi-detached house?

It usually adds value, but the gain is never certain. Nationwide's 2025 research found that 10% more floor area was linked to about 5% higher value, and that adding a double bedroom and bathroom to a three-bed, one-bathroom house could add up to 24%. Every street has a ceiling price, so check local sales first.

What if my neighbour has already extended?

That often helps. An existing extension next door can reduce the effect of yours on their light, and may show what the council accepts on your street. It can also mean building alongside their wall, so we check its position, foundations and any windows facing your plot at the survey.

Nearby

Close to St Ives? We work across the area, including:

Other extensions in St Ives

All two-storey extension services in St Ives · Two-storey extensions for semi-detached houses across Cambridgeshire

Send us your postcode and a few details. We'll get back to you to arrange a visit and talk through your options.