What an extension costs in Teesside in 2026
A single-storey rear extension in Teesside costs £1,900 to £2,600 per square metre and a two-storey £1,700 to £2,300, so a 20m² kitchen-diner extension typically lands between £38,000 and £52,000. Professional fees add 8 to 12 per cent, and a 10 per cent contingency is realistic on any job that opens up ground.
Last updated: August 2026.
Why local rates are lower than the national figures
National extension cost articles quote £2,500 to £3,500 per square metre because they are weighted towards London and the South East. Labour rates on Teesside sit meaningfully below that, materials cost roughly the same everywhere, and the result is that regional build rates come in around 20 to 30 per cent under the national average. That is the single reason extending makes financial sense here in cases where it would not in the South.
It also means the quotes you receive locally should land in a fairly tight band once specification is fixed. A spread of 10 to 15 per cent between comparable quotes is normal. A spread of 40 per cent means the quotes are not describing the same job, and the right response is to compare the specifications rather than the totals.
The full budget, not just the build
Build cost is roughly 80 per cent of what an extension actually costs. The other lines are predictable and routinely missed:
- Architectural drawings: £1,200 to £3,500 for a householder scheme, depending on whether you buy planning drawings only or a full technical package.
- Structural engineer: £400 to £900 for beam and foundation calculations.
- Planning application fee: £258 for a householder application at current rates, or £145 for a lawful development certificate.
- Building control: £600 to £1,100 for a typical extension, via the council or an approved inspector.
- Party wall surveyor: nothing if neighbours consent in writing, £900 to £2,000 per adjoining owner if an award is needed.
- Build-over agreement: a few hundred pounds where a public sewer is affected, plus time.
- Kitchen, bathroom and furniture: almost always excluded from a builder's price and frequently the largest forgotten number.
- Contingency: 10 per cent. On a house older than 1950, closer to 15.
What moves the price most
Glazing. The gap between a good uPVC French door set and a six-metre aluminium bifold run with a structural head is easily £8,000 to £15,000. Rooflights are a cheaper way to buy light and are structurally simpler.
Foundations. Standard trench fill at 900mm to 1.2m is the assumed case. Mature trees within influencing distance, made ground or a nearby sewer can drive depth to 2.5m or force piling, and a metre of extra depth across a 20m² footprint is thousands, not hundreds. This is why honest quotes contain a provisional sum for foundations with a stated rate per cubic metre.
Structural openings. Removing most of the existing rear wall to open the extension into the house needs steel, padstones and sometimes a goalpost frame. It is worth every penny in terms of how the finished space feels, and it should be priced explicitly rather than assumed.
Level changes and drainage diversion. Sloping gardens, raised patios and inspection chambers in the wrong place all add groundwork.
VAT, and the one exception worth knowing
Extension work to an existing dwelling carries VAT at 20 per cent. Two reliefs are relevant locally. A property that has been empty for two years or more attracts a reduced 5 per cent rate on renovation work, which matters a great deal on the region's stock of long-vacant terraces. New-build dwellings are zero rated, and self-builders can reclaim VAT on materials through the DIY housebuilders scheme. Where a builder is not VAT registered there is no VAT at all, though on a project of this size that is unusual and worth understanding rather than assuming.
Payment structure that protects both sides
On a £45,000 job, payment should follow completed work. A workable pattern is 10 per cent on commencement for materials and set-up, then staged payments at damp-proof course level, roof watertight, first fix complete, plastering complete, and a final payment on completion with 2.5 to 5 per cent retained for four to eight weeks against snagging. Large up-front deposits are the warning sign; so is any request to pay ahead of work done.
Is it worth it against moving?
Compare the extension cost against the true cost of moving to a larger house. On a £300,000 purchase, stamp duty, agency fees, legal costs, survey and removals typically consume a substantial five-figure sum that buys no additional space whatsoever. Against that, £45,000 spent on a kitchen-diner extension usually adds real value and always adds usable space. The caveat is the street ceiling: on roads where nothing sells above a certain figure, spending past that point buys enjoyment rather than equity, which is a perfectly good reason to do it but a bad reason to borrow heavily.
Ready to price your own project? Extension specifications and options are set out in more detail, and the planning and building regulations guide covers the approvals.
| Extension type | Rate per m² | Typical total |
|---|---|---|
| Single-storey rear, standard spec | £1,900–£2,200 | £38,000–£44,000 (20m²) |
| Single-storey rear, high spec | £2,300–£2,600 | £46,000–£52,000 (20m²) |
| Side infill extension | £2,000–£2,500 | £20,000–£30,000 (10–12m²) |
| Wrap-around | £2,000–£2,500 | £60,000–£85,000 (30–34m²) |
| Two-storey rear or side | £1,700–£2,300 | £68,000–£92,000 (40m²) |
| Orangery or garden room | £1,600–£2,100 | £26,000–£38,000 (16m²) |