GDV Calculator Changelog | Data Refresh Log

2026-11-13 - Regional build costs from council-published BCIS figures

Every regional build cost now comes from a BCIS £/sqm table reprinted in a named council viability study, rebased to that area and dated: Wandsworth, Medway (Kent), Cotswold, Castle Point, Derbyshire Dales, Rugby, York, Oldham, Tees Valley and Cardiff. Each region shows the estate housing lower quartile, median and upper quartile, and the flats median where published.
Scotland shows the build-cost range the Valuation Office Agency adopted for Cairngorms National Park sites (October 2024). Northern Ireland has no public figure, so its page and the calculator ask for your own rate.
The BCIS build cost calculator adds a houses or flats choice, an external works uplift and your own rate. The North West = 100 regional index is gone: BCIS sets location factors against a UK mean of 100.
Tower Hamlets E14: zones now follow the council's CIL charging-zone map (Canary Wharf and the northern Isle of Dogs Zone 1, the southern Isle of Dogs Zone 2).

Borough CIL on the six London pages now comes from each council's Annual CIL Rate Summary and zone map: Wandsworth 2026 (£448.43/sqm outside Nine Elms), Lewisham 2026 (Zone 2 £108.10/sqm for SE13), Tower Hamlets 2026 (Zone 1 £335.33/sqm), Southwark 2026 Part 2 and Camden 2025 (Zone C £753/sqm).
Southwark's third charging schedule took effect on 29 September 2026; SE1 now shows the new Zone 1 rate of £598/sqm, with Zone 2 at £300/sqm.
Hackney publishes no annual summary, so its E8 figure is the 2015 Zone A rate of £190/sqm indexed with the RICS CIL index (£293.44/sqm), with the method shown on the page.
Each borough page now lists its council's rate summary under Sources of record. The BCIS regions page links straight to the BCIS build cost calculator.

NPPF vintage updated to the August 2026 framework (published 17 Aug 2026, the first comprehensive rewrite since 2012), superseding the Dec 2024 (amended Feb 2025) framework across every viability, methodology and scheme-type page.
New NPPF 'medium development' band recorded on the small-sites page: 10 to 49 homes on sites up to 2.5ha (Annex B); medium schemes remain major development unless a policy states otherwise, so the BNG and statutory-consultation major/minor split still turns on the 10-dwelling / 0.5ha line.
PPG-Viability vintage updated to last-updated 16 Dec 2025; the 15 to 20 percent PoGDV developer-return range (17.5 percent midpoint, paragraph 019) is unchanged.
Bank Rate held at 3.75 percent (BoE held 17 Sep 2026 on a 6-3 vote); no change to finance-cost inputs.

Bank Rate corrected to 3.75 percent (BoE held 18 Jun 2026); previously 4.00.
NPPF vintage corrected to Dec 2024 (amended Feb 2025) as the in-force framework; the Dec 2025 revision is a draft (consultation closed 10 Mar 2026), final expected Summer 2026.
PPG-Viability developer return restated as the 15 to 20 percent GDV range (17.5 percent midpoint), matching the guidance wording.
BNG statutory credit prices restated as £42,000 (tier A1, cheapest) to £650,000 (tier A5); the new 0.2ha small-site exemption and removal of the self-build exemption from 6 Aug 2026 added.

Initial workbench shipped with 12 BCIS regions and 6 London borough deep-dives.
BCIS Q2-2026 build-cost bands wired in.
NPPF Dec 2024 + PPG-Viability Dec 2024 viability framing applied across the cost-line pages.
9 scheme-type presets loaded.
5-by-5 sensitivity heatmap on the hero.

Draft revised NPPF published 16 Dec 2025 for consultation (closed 10 Mar 2026); final expected Summer 2026. In-force framework remains NPPF Dec 2024 (amended Feb 2025).
PPG-Viability 15 to 20 percent PoGDV range (17.5 percent midpoint) applied across viability and developer-return pages.