GDV: calculating gross development value a lender will believe

Gross development value — the total expected revenue from selling the finished scheme — is the number every other appraisal line hangs off. Profit is a percentage of it; the land bid is the residual after subtracting costs from it. An unsupported GDV makes the whole appraisal fiction.

The method

1. Per house type, establish achievable £/sqft from local, indexed, size-weighted evidence with the local new-build premium applied.
2. Multiply by planned internal area for each unit type — e.g. £455/sqft × 1,400 sqft = £637,000 per detached unit.
3. Sum across the mix. 10 detached + 14 semis + 8 terraces, each priced from its own evidence, not one blended rate.
4. State it as a range. Evidence gives you low/mid/high; a single-point GDV overstates your certainty.

Errors that get GDVs discounted

• One blended £/sqft across all types. Flats and detached houses do not earn the same rate; blending flatters whichever dominates your mix.
• Asking prices as evidence. Lenders know asking is not achieved. Sold, completed, registered prices only.
• Premium double-counting — applying a new-build premium to comps that were already new-build sales.
• No absorption sanity check. A GDV that requires selling 4 units/month in a market absorbing 1.5 is really a discounting-and-incentives forecast.

The test a good GDV passes: every unit price traces to named comparable evidence, indexed to today, with the adjustments visible. That traceability is exactly what Threshold's appraisal export is built to show.

Data referenced in Threshold is displayed under the Open Government Licence (HM Land Registry Price Paid Data, EPC Register, ONS, UK HPI). All figures produced by Threshold are statistical estimates for site appraisal, not RICS valuations.