Two-storey side extensions in County Durham

What a two-storey side extension involves

A two-storey side extension is a new two-floor addition built into the space beside your house, often over a driveway or side passage. It typically adds one or two bedrooms upstairs and a utility, study or larger kitchen below, without giving up rear garden.

County Durham towns we list: Darlington (DL1), Hartlepool (TS24), Stockton-on-Tees (TS18), Durham (DH1), Chester-le-Street (DH2) and Billingham (TS20). Every other address in County Durham is covered as well.

Guide price in North East England

Most of the cost of a two-storey side extension is set by its size and specification. For County Durham and the rest of North East England, our guide is £1,840–£2,480 per m² including VAT, so about £77,500–£104,000 for a 3 m × 7 m footprint on two floors (42 m² of new floor space). Keep a contingency of around 10% for things nobody can see until the ground is opened up.

Rules in England

In England, a two-storey side extension always needs householder planning permission, because permitted development only allows single-storey extensions beyond a side wall. The fee is £548 (or £575 for applications made from 8 December 2026), and councils should decide within 8 weeks of validation. Expect them to look at set-back, roof height, gaps to the boundary and the effect on neighbours.

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

Set-down and set-back

Councils usually want a two-storey side extension to look subordinate to the house. Setting the front wall back from the main front and dropping the ridge slightly below the main roof helps it read as an addition, and is often expected in local design guidance.

Matching the ridge and roof

A hipped house usually needs a hipped extension roof, and a gabled house a gable. Matching the pitch, tiles, ridge detail and brick bond is what makes a side extension look original rather than added, and councils look closely at it on a front-facing addition.

How we work in County Durham

1. Start at your house

   We come to your home in County Durham, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.

2. Get it approved

   Once you're happy with the design we submit it to the council for County Durham and deal with any questions from the planning officer.

3. Engineer it

   Foundations sized for two floors, steels for any openings, and building control approval, all before anyone starts on site.

4. On site

   One project lead runs the job, keeps you updated and arranges inspections at each stage until completion.

Towns we cover in County Durham

• Darlington
• Hartlepool
• Stockton-on-Tees
• Durham
• Chester-le-Street
• Billingham
• Stanley
• Consett
• Newton Aycliffe
• Bishop Auckland
• Seaham
• Thornaby-on-Tees
• Peterlee
• Yarm
• Spennymoor
• Annfield Plain
• Shildon
• Ferryhill
• Brandon

Neighbouring areas

• Two-storey side extensions in Tyne and Wear
• Two-storey side extensions in Northumberland
• Two-storey side extensions in North Yorkshire
• Two-storey side extensions in West Yorkshire

All extension services in County Durham · About two-storey side extensions