How much does an extension cost in Teesside? (2026)
Extensions in Teesside cost roughly £1,900 to £2,600 per square metre in 2026, putting a single-storey addition at £25,000 to £45,000 and a two-storey at £40,000 to £70,000. Ground conditions, roof form, glazing and the finish standard account for almost all of the variation.
Read the rate, not the headline
Builders price extensions per square metre because it is the only figure that survives comparison. In 2026 a sound Teesside build sits between £1,900 and £2,600 per square metre for the shell and internal finishes to a good standard, excluding kitchens and top-end glazing. Small extensions come in above that range because foundations, scaffolding, roof edges and site set-up cost much the same whether the room is 12 or 25 square metres. Two-storey work drops below it, since a single set of foundations and a single roof serve two floors, which is why adding upstairs as well as down often improves the value even though the total cheque is larger.
What moves the price
- Ground: made ground on the old industrial fringes, a mature tree within influencing distance, or a drain crossing the footprint each add depth, concrete or a diversion. A trial hole before quoting turns a guess into a figure.
- The opening into the house: a steel beam with padstones, temporary support and making good is £2,000 to £10,000 on its own, and some quotes exclude it. Check.
- Roof: a tiled mono-pitch is the cheapest. A flat roof with a lantern costs more, and cutting a new hipped roof into the existing one costs more still.
- Glazing: a modest patio door versus a 4 metre aluminium bifold with a rooflight above is a five-figure decision.
- Finish and fit-out: underfloor heating, engineered oak, a full utility and a £20,000 kitchen belong on the quote as separate lines so you can trim without renegotiating the shell.
- Access: a terrace with a shared alley means everything in and out by wheelbarrow, and skips need a permit for the highway. That is real labour cost.
Worked examples by Teesside house type
Interwar semi, Acklam or Norton, 20 m² rear plus side infill. Trench-fill foundations, cavity walls to match, mono-pitch tiled roof, 3 metre steel to open the back of the house, bifolds to the garden, plastered and decorated, kitchen supplied by the homeowner. Roughly £42,000 to £55,000 with a mid-range kitchen fitted.
Victorian terrace, Linthorpe or Hartlepool, 12 m² rear infill. Small footprint, awkward access down a shared alley, party wall notices to two neighbours, existing drainage to work around, and a lime-compatible approach where new brick meets old. Roughly £26,000 to £34,000, and the per-metre rate is the highest of any example here.
Detached on a newer estate, Ingleby Barwick or Wynyard, 30 m² two-storey side. Matching brick and tile to the developer's original, a bedroom and en-suite over a family room, and a planning application rather than permitted development if the original allowance has already been used. Roughly £55,000 to £70,000.
Costs people forget to budget
Architect or technician drawings £1,200 to £3,000. Structural engineer's calculations £300 to £700. Planning application fee where one is needed, plus a separate building regulations fee. Party wall surveyor if a neighbour dissents, £900 to £2,000. Skip permits, temporary kitchen arrangements, and the decoration of the rooms that adjoin the new space, which always looks tired next to fresh plaster. Adding ten per cent as a contingency is not pessimism, it is how experienced clients budget.
Comparing quotes fairly
Ask every firm to price the same drawing, itemised the same way, with exclusions written down. Then read what is missing rather than what is included: the cheapest of three quotes is very often the one that left out the steel, the drainage diversion or the making good. Detail on that process is in choosing a builder, the permissions side is covered in planning permission on Teesside, and the service page for house extensions sets out what the work involves.
| Type | Typical price | Rate per m² |
|---|---|---|
| Single-storey rear, 15 m² | £25,000–£34,000 | £1,900–£2,600 |
| Single-storey rear, 25 m² | £35,000–£45,000 | £1,800–£2,300 |
| Wraparound side and rear, 30 m² | £45,000–£65,000 | £1,900–£2,500 |
| Two-storey side or rear, 30 m² | £40,000–£70,000 | £1,500–£2,200 |
| Porch or small utility addition | £8,000–£15,000 | n/a |
| Structural opening into the house | £2,000–£10,000 | n/a |
| Kitchen supply and fit (separate) | £8,000–£30,000 | n/a |