Cost guide · London 2026
Prices for 2026, from the jobs we've priced and built this year. Choose your house and the loft you're thinking about below. You'll get a range including VAT, the weeks on site, and what to expect before we start.
The estimator couldn't load. The base prices are in the table below, and the office can give you a figure on 020 7946 0196.
For a two-storey Victorian mid-terrace about 4.6 m wide with a two-storey back addition (hip-to-gable: an end of terrace). Including VAT, design and council fees. Without a bathroom.
| Loft type | Price range | On site | Floor area added | Usual route |
|---|---|---|---|---|
| Rooflight conversion | £42,000 to £56,000 | 6 to 8 weeks | 14 to 20 m² | Permitted development |
| Rear dormer | £64,000 to £80,000 | 9 to 11 weeks | 22 to 28 m² | Permitted development |
| L-shaped dormer | £80,000 to £98,000 | 11 to 13 weeks | 30 to 38 m² | Permitted development |
| Hip-to-gable with rear dormer | £84,000 to £104,000 | 11 to 14 weeks | 28 to 36 m² | Permitted development |
| Mansard | £108,000 to £135,000 | 14 to 17 weeks | 30 to 38 m² | Planning permission |
| Fee | Amount | Who pays |
|---|---|---|
| Lawful development certificate (council) | £274 | Included in our price |
| Householder planning application (council) | £548 | Included in our price |
| Prior approval, larger home extension (council) | £249 | Included in our price |
| Building control (Haringey, loft conversion, 2026/27 standard charge) | £926 plus VAT | Included in our price; other councils charge similar amounts |
| Party wall surveyor, one agreed surveyor for both sides | About £1,100 to £1,600 per neighbour | Paid by you, directly to the surveyor |
| Party wall surveyors, where the neighbour appoints their own | About £1,900 to £3,000 per neighbour | Paid by you; the building owner normally pays both surveyors |
If your neighbours consent in writing to the party wall notice, there's no surveyor and no fee. About half of our neighbours do. We meet them with the drawings before the notices go out, which helps.
Council fees are those published for England from 1 April 2026 and can change. Building control charges differ by council. Check with your local authority for your own figures.
Two houses on the same street can differ by £15,000 for reasons you can't see from the pavement. The ones we find most often: party walls that stop below the roof line and have to be built up before steel can sit on them; chimney breasts removed downstairs years ago and left unsupported above; a stair that has to turn to find the headroom; a soil stack on the wrong side for the bathroom; and roofs repaired so many times that little of the original timber is worth keeping. We'd rather show you a wide range now than a low number that grows.
The same arithmetic the estimator uses, written out line by line.
MID-TERRACE · REAR DORMER · SHOWER ROOM · STANDARD STAIR · STRUCTURE NOT KNOWN · PERMITTED DEVELOPMENT
| Base, rear dormer | £64,000 to £80,000 |
|---|---|
| Shower room | +£9,500 to +£14,000 |
| Structure not known | +£0 to +£2,500 |
£73,500 to £96,500
ON SITE 10 to 12 weeks · BEFORE WE START 10 to 16 weeks
Party wall: two neighbours, £0 to £6,000; about £2,200 to £3,200 with one agreed surveyor.
SEMI-DETACHED · HIP-TO-GABLE · BATHROOM · TURNED STAIR · EXTRA STEEL · CONSERVATION AREA
| Base £84,000 to £104,000 x 1.03 | £86,520 to £107,120 |
|---|---|
| Conservation materials | +£5,040 to +£12,480 |
| Bathroom | +£13,500 to +£19,000 |
| Turned stair | +£2,800 to +£4,800 |
| Extra steel | +£4,500 to +£9,000 |
| Planning drawings and fee | +£2,800 to +£4,800 |
£115,000 to £157,500
ON SITE 13 to 16 weeks · BEFORE WE START 18 to 28 weeks
Party wall: one neighbour, £0 to £3,000.
Extensions vary more than lofts, so we don't run them through the estimator. As a guide, our extensions come out at about £3,200 to £4,300 per square metre including VAT, before kitchen units.
| Extension | Price including VAT | On site |
|---|---|---|
| Side-return extension | £68,000 to £95,000 | 12 to 14 weeks |
| Single-storey rear extension (up to 3 m) | £72,000 to £98,000 | 11 to 13 weeks |
| Larger rear extension under prior approval (up to 6 m) | £95,000 to £135,000 | 13 to 16 weeks |
| Wraparound extension (side return plus rear) | £115,000 to £165,000 | 15 to 18 weeks |
| First-floor extension over the back addition | £55,000 to £80,000 | 10 to 12 weeks |
Book a survey visit. We'll measure, look at the party walls and the stair, and send a written budget within five working days. The design stage follows if you want to go ahead.