How to Calculate GDV: Gross Development Value Explained

Gross Development Value (GDV) is the total market value of a completed development. For a residential scheme, it's the sum of all individual unit sales. For a commercial development, it's the investment value based on the capitalised rental income. For a mixed-use scheme, it's both combined.

GDV determines everything: how much you can borrow, whether your scheme is viable, and ultimately whether you make a profit. Development finance lenders express their maximum loan as a percentage of GDV (LTGDV) — typically 60-70% for senior debt. A £5M GDV scheme at 65% LTGDV generates a maximum facility of £3.25M.

This is why getting GDV right is critical. Overestimate GDV and you'll borrow too much, build a scheme that doesn't stack, and potentially default on your facility. Underestimate it and you'll leave money on the table or fail to secure adequate funding.

For residential developments, GDV is calculated using comparable sales evidence — recent sales of similar properties in the same area. The key word is 'comparable'. A new-build 3-bed semi in a suburban development is not comparable to a period 3-bed semi in an established street, even if they have the same number of bedrooms.

The most reliable comparables are: new-build sales by other developers in the immediate area (within 0.5 miles), recently completed schemes of similar specification, and Land Registry data for the specific postcode sector. Adjust for differences in specification, garden size, parking, and aspect.

Apply a per-square-foot rate to your proposed scheme. If comparable new builds in the area sell at £350/sq ft and your units average 850 sq ft, each unit is worth approximately £297,500. For a 12-unit scheme, GDV is £3.57M. Always sense-check this against the market — are there enough buyers at this price point in this location?

Your lender will instruct a RICS-registered valuer to provide a formal Red Book valuation of your site and proposed scheme. This valuation is independent of your own GDV estimate and is the figure the lender will use to calculate your maximum facility.

The valuer will assess: the site in its current condition (the 'site value'), the completed development value (the GDV), the build costs and programme, and the developer's profit margin. They may disagree with your GDV estimate — and their figure is the one that matters to the lender.

If the valuer comes in significantly below your estimate, it doesn't necessarily mean your scheme is unviable. It may mean the valuer has used more conservative comparables, applied a different per-square-foot rate, or made different assumptions about specification. You can challenge a valuation with additional evidence, but ultimately the lender relies on their appointed valuer.

Using asking prices rather than achieved prices. Estate agent asking prices are aspirational — they're the price the agent hopes to achieve, not what buyers actually pay. Always use Land Registry sold prices or verified sales data from property portals.

Comparing to different property types. A converted flat is not comparable to a new-build flat. A terraced house is not comparable to a detached house. A garden flat is not comparable to a top-floor flat. The more specific your comparables, the more credible your GDV.

Ignoring new supply. If another developer is building 200 new homes in the same postcode, their scheme will absorb buyer demand. Your sales rate and achievable prices may be lower than current comparable evidence suggests. Lenders and valuers check planning applications for competing schemes.

Applying London or South East values to regional markets. A developer who achieves £500/sq ft in Surrey should not expect the same in Staffordshire. Regional price differentials are well-established and lenders will immediately flag unrealistic GDV assumptions.