Two-storey annexe extensions in Bedfordshire

Bedfordshire at a glance

Nation: England
Price region: East of England
Postcode areas: LU, MK, SG
Towns covered: 11 listed below, plus surrounding villages
Approval route: Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.
Site visits: Free, no obligation

What a two-storey annexe extension involves

A two-storey annexe extension is an attached extension laid out as self-contained living space on two floors, usually with a living area and kitchenette below and a bedroom and shower room above, for a relative living with the family. It stays part of the main house rather than a separate home. Planning and council tax rules treat it differently from a separate dwelling.

The main places we list in Bedfordshire are Luton (LU1), Bedford (MK40), Dunstable (LU5), Leighton Buzzard (LU7), Ampthill (MK45) and Kempston Hardwick (MK42). We cover the villages in between too.

Guide price in the East of England

A guide price for Bedfordshire: around £88,500–£119,000 (plus kitchenette and shower room fittings, priced to your choice) for a 3 m × 7 m footprint on two floors (42 m² of new floor space). That works out at £2,110–£2,830 per m² of new floor space, including VAT at 20%. Professional fees for drawings and the structural engineer are listed separately on our prices page.

Spec	Per m²	Typical project
Essential	£1,940–£2,610 per m²	£81,500–£109,500
Standard	£2,110–£2,830 per m²	£88,500–£119,000
Premium	£2,530–£3,400 per m²	£106,500–£143,000

Rules in England

In England, an annexe on two floors is assessed like any two-storey extension: at the rear it 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, but at the side it needs planning permission, costing £548 (or £575 for applications made from 8 December 2026). Councils often add a condition that the annexe stays ancillary to the main house and is not let separately.

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.

The Party Wall etc. Act 1996 applies, so notices may be needed for work on or near a shared wall or boundary.

Getting the design right

Ground-floor living for the future

Many annexes are planned so the occupant could live on the ground floor if stairs become difficult. A ground-floor bedroom space, a level-access shower and wider doorways cost little at the design stage and are expensive to add later.

Fire separation and escape

A kitchenette in an annexe and a bedroom above need safe escape and suitable separation from the main house. Building control checks the escape windows, smoke alarms and the door between the two parts.

How we work in Bedfordshire

Start at your house
We come to your home in Bedfordshire, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
Choose the approval route
Some designs fit permitted development, most need a householder application. We decide which applies in England before drawing in detail.
Technical design
We prepare the building regulations drawings, structural calculations and specification so the build price can be fixed.
On site
One project lead runs the job, keeps you updated and arranges inspections at each stage until completion.

Towns we cover in Bedfordshire

Two-storey annexe extensions in Bedfordshire: questions

How much does a two-storey annexe extension cost in Bedfordshire?

In the East of England our guide is £2,110–£2,830 per m² including VAT, so about £88,500–£119,000 (plus kitchenette and shower room fittings, priced to your choice) for a 3 m × 7 m footprint on two floors (42 m² of new floor space). Essential and Premium specs move that by roughly 8% down or 20% up.

Can an annexe have its own front door?

It can, but a separate front door, kitchen and address together make it look more like a separate home, which can change how the council treats it for planning. Many annexes have their own door to the garden or side and an internal door to the main house. We explain how each choice is likely to be viewed before the design is fixed.

Can I rent out an annexe later?

Not always. Many annexe permissions include a condition that it is only used by members of the household, so renting it out may need a fresh planning application. If you think you might want to let it, tell us at the start so we can explain the options.

Can an annexe be designed for someone with limited mobility?

Yes. We can plan a ground-floor bedroom space, a level-access shower, wider doorways, lever handles and space for a stairlift later. These features are much cheaper to build in at the start than to add afterwards, and they keep the annexe useful as needs change.

Will I need planning permission in Bedfordshire?

Bedfordshire is in England. Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.

Neighbouring areas

All extension services in Bedfordshire · About two-storey annexe extensions