Independent reference. UK figures verified 21 June 2026. No vendor affiliation.
Direct answer

Knockdown rebuild cost (UK)

A UK knockdown rebuild typically costs £1,800 to £2,800/sqm in the South East for the build above slab[BCIS Q2 2026], plus £8k to £15k to demolish[FMB 2026], plus £10k to £25k in professional fees. A 200 sqm South East mid-tier replacement lands at £640k to £870k all-in (£480k-£600k build above slab; the rest is demolition, asbestos, foundations, fees, planning, BC, 12 months temp accom, and contingency), and pays no VAT[HMRC 708].

0% VAT. New dwelling (VAT Notice 708)

Oliver Wakefield-Smith. Updated 21 June 2026. Reviewed against BCIS Tender Price Index Q2 2026 and HMRC VAT Notice 708 (June 2025 revision).

80200 (typical)400
Demolition + Statutory
£74.6k to £123.8k
  • Demolition + Section 80 notice£14k to £22k
  • Asbestos R&D survey + removal£850 to £3.5k
  • Professional fees (architect, SE, PW)£57.6k to £90k
  • Planning fees + CIL + Section 106£1.2k to £6.5k
  • Building Control fees£950 to £1.8k
Build + Move-in
£564.4k to £744k
  • Foundations + ground investigation£15k to £25k
  • Build above slab (sqm x £/sqm x region)£480k to £600k
  • Temporary accommodation (months x rent)£21.4k to £29k
  • Contingency (10-15% of build)£48k to £90k
VAT saved vs equivalent extension£96k to £120k
All-in (zero VAT)£639k to £867.8k
200 sqm in South East, mid tier£3.2k to £4.3k per sqm all-in
The 8 phases
1Surveywk 0 to 42Demowk 4 to 83Foundationswk 8 to 144Shellwk 14 to 2851st Fixwk 28 to 3662nd Fixwk 36 to 467Snagwk 46 to 508Movewk 50 to 52

Eight-phase typical KDR sequence. Total elapsed 50 to 56 weeks for a 200 sqm replacement.

What you are deciding, in order

1

Should I knockdown rebuild at all?

The honest comparators are extension, full renovation, and sell-and-buy-up. KDR wins on £/sqm above roughly 90 sqm of new floor area, wins decisively on VAT[HMRC 708], and loses on listed or conservation-area plots. The full decision tree.
2

How much, all-in?

The calculator above returns a defensible range. Show your architect the worked example: £/sqm by tier, plus demolition, foundations, architect and structural engineer fees, temporary accommodation, and contingency.
3

Where am I building?

BCIS regional multipliers swing the headline £/sqm by up to 55%. London +45%, South East +20%, Yorkshire 8% below the UK average[BCIS Q2 2026]. Pick your region from the 12-option grid in the calculator, or read the dedicated regional page: London, Surrey, Kent, Hertfordshire, Buckinghamshire.
4

What stage am I at?

Sequence: survey, demolition, foundations, shell, first fix, second fix, snag, move. The timeline page walks through each phase. The cashflow page maps your stage-payment schedule onto a self-build mortgage or bridging facility.
5

What is the catch?

VAT is straightforward once you read Notice 708. Planning, CIL, party-wall, asbestos, and the Future Homes Standard are not. Planning, CIL and Section 106, Party Wall Act, HSG264 asbestos survey, FHS 2025/26.

Why a defensible number matters

By the time a homeowner reaches RIBA Stage 2, two architects, one quantity surveyor, and a partner have all quoted different totals. The calculator above is anchored to BCIS Q2 2026 tender prices[BCIS], FMB regional labour rates[FMB 2026], and HMRC VAT zero-rating[HMRC 708]. Every figure on the site is traced to a primary source. The ledger lives at /sources.

Demolition is the cheap bit. The asbestos survey is what surprises people.

Next decisions