Residual land value: the arithmetic behind viability
Value of the finished scheme, less costs, less the developer's return, equals what the land can bear. The dispute is never about the formula, always about the inputs.
Residual land value is what is left when you take the value of the finished scheme, subtract everything it costs to build and sell, and subtract the return the developer needs. Whatever remains is what the land can bear. Viability testing then compares that residual figure against a benchmark land value, and if the residual sits below the benchmark, the argument is that the scheme cannot carry the full policy package of affordable housing and obligations.
Every part of that sentence is contested in practice, which is why viability disputes take months.
What the residual method actually does
The arithmetic is simple and the inputs are not.
Gross development value, minus construction costs, minus professional fees, minus finance, minus marketing and sales costs, minus the Community Infrastructure Levy and section 106 obligations, minus developer's profit, equals residual land value.
Two features of the method matter more than the formula. It is highly sensitive: a two per cent movement in sales values or a five per cent movement in build costs can swing the residual by a much larger proportion, because the residual is a small difference between two large numbers. And it is a snapshot at a stated date, which is why review mechanisms exist.
National guidance expects viability to be dealt with primarily at plan-making stage, with site-specific assessment the exception rather than the rule. Where a scheme complies with all relevant policies and the plan's viability testing was sound, the starting point is that the scheme is viable. An applicant arguing otherwise has to explain what has changed.
Gross development value and its evidence base
Gross development value is the aggregate value of everything the scheme produces: market homes, affordable homes sold to a registered provider at a transfer value, and any commercial floorspace capitalised at an appropriate yield.
Evidence it with comparables, not with aspiration. Councils and their reviewers look for recent transactions of similar property in the same market, adjusted for date, size, specification and location, with the adjustments shown. New-build premiums are argued about constantly and should be evidenced rather than assumed.
The affordable transfer value is the input applicants most often get wrong. It should reflect what a registered provider would actually pay in that area for that tenure mix, supported by a letter or a bid rather than a percentage of open market value taken from a textbook.
Where the scheme includes commercial space, be honest about void periods and incentives. A ground-floor retail unit valued as fully let from day one, in a town where similar units sit empty, is the kind of input that costs credibility across the whole appraisal.
Build costs, contingency and fees
Construction costs normally come from a published cost index for the building type and location, adjusted to the date of the appraisal, or from a quantity surveyor's measured estimate on a designed scheme.
Reviewers scrutinise five items in particular.
- Abnormals: demolition, remediation, piling, retaining structures, service diversions. Each needs supporting evidence, because abnormals are where costs are inflated most easily.
- External works and infrastructure, which on a greenfield site can be a large proportion of the total and is often understated in early appraisals.
- Contingency, which is a legitimate cost but is challenged when it sits above the level the risk profile justifies.
- Professional fees, typically expressed as a percentage of construction cost, with the percentage falling as scheme size rises.
- Policy-driven costs, including biodiversity net gain delivery, sustainability requirements and any local space or design standards.
Do not double count. Contingency that also appears inside individual cost lines, or a policy cost that is already in the base build rate, is the first thing a reviewer looks for.
The developer's return
Profit is a cost in a residual appraisal, not an outcome. National viability guidance indicates that a return of 15 to 20 per cent of gross development value may be considered a suitable return to developers when establishing the viability of plan policies, and that a lower figure may be appropriate on the affordable housing element, in recognition of its lower risk.
Those figures are a starting point, not a rule. The percentage is argued on risk: scheme size, phasing, market depth, whether sales are pre-let or speculative, and how long the money is out. A build-to-rent scheme, a single-phase scheme with a forward-funded purchaser, and a ten-year phased regeneration site do not carry the same risk and should not carry the same return.
Expect the reviewer to test profit on cost as well as profit on value, because the two produce different answers and applicants tend to quote whichever is lower.
Benchmark land value and betterment
The residual figure means nothing on its own. It is compared with the benchmark land value, which national guidance approaches as existing use value plus a premium: the value of the land in its current use, plus a premium sufficient to persuade a reasonable landowner to sell.
The premium is where most disputes live. It should reflect the minimum a landowner would accept, informed by market evidence of transactions on comparable sites, and it must account for the policy requirements of the development plan. A benchmark set by reference to what the landowner was offered by another developer, on the assumption of a policy-light scheme, is circular.
Betterment is the underlying idea. Granting permission creates an uplift in land value, and policy captures a share of that uplift through affordable housing, section 106 obligations and the Community Infrastructure Levy. The land value that matters for viability is the value after those obligations, not before, which is why the price paid for a site is not a valid input.
An Affordable Housing Statement sets out what is being offered. A Viability Assessment is the document that explains why it is less than policy, and national guidance expects such assessments to be prepared transparently and, in most cases, published in full.
An illustrative residual calculation
Illustrative example, using round numbers to show the method rather than to state market values. A nine-unit scheme on a brownfield plot.
| Line | Illustrative figure |
|---|---|
| Gross development value | £3,600,000 |
| Construction cost | £1,980,000 |
| Abnormals, including remediation | £150,000 |
| Professional fees at 10 per cent of build | £198,000 |
| Finance and marketing | £190,000 |
| Section 106 and levy | £80,000 |
| Developer's return at 17.5 per cent of value | £630,000 |
| Residual land value | £372,000 |
If the benchmark land value is £350,000, the scheme is viable as configured and the obligations stand. If the benchmark is £500,000, the applicant argues for a reduced affordable contribution, and the council's reviewer will test the abnormals, the return and the benchmark before accepting it.
Change the construction cost by five per cent and the residual moves by around £100,000, which is more than a quarter of it. That sensitivity, rather than any single input, is the reason these arguments are so hard fought.
Review mechanisms
Because the appraisal is a snapshot, councils increasingly secure review mechanisms in the section 106 agreement.
An early-stage review triggers if the scheme has not been implemented within a set period, testing whether market movement has improved viability. A late-stage review at a defined point before final sales tests the outturn against the appraisal, with any surplus shared according to a formula and usually capped at the full policy requirement.
Two drafting points make the difference. Define the trigger dates and the calculation in the agreement itself, with a worked pro forma appended, rather than leaving the method to be agreed later. And agree how disputes are resolved, because a review clause with no expert determination provision produces a stalemate exactly when the money is at stake.
Browse the 66 PlanScope report types to see which supporting documents a scheme of this kind needs, and see PlanScope pricing for what a draft costs to produce as a starting point for your appointed valuer. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval, and for specialist technical reports qualified professional input may be required. This is general guidance rather than legal advice.
Frequently asked questions
How is residual land value calculated?
Take gross development value, then deduct construction costs, abnormals, professional fees, finance, marketing and sales costs, the Community Infrastructure Levy and section 106 obligations, and the developer's return. What remains is the residual land value, which is then compared against a benchmark land value to test whether the scheme can carry the full policy package.
What developer return is accepted?
National viability guidance indicates that a return of 15 to 20 per cent of gross development value may be suitable to establish the viability of plan policies, with a lower figure appropriate on affordable housing because it carries less risk. Those are starting points, argued on scheme size, phasing, market depth and how long capital is committed.
Can I use the price I paid for the land as the benchmark?
No. The benchmark land value is approached as existing use value plus a premium sufficient to persuade a reasonable landowner to sell, informed by market evidence and taking account of the policy requirements of the development plan. A price paid on the assumption of a policy-light scheme is circular and reviewers reject it.
Does a viability assessment have to be published?
National guidance expects viability assessments to be prepared transparently and, in most cases, made publicly available in full, with only limited scope for redaction. Assume publication when you write one, because an assessment prepared on the basis that nobody outside the council will read it tends to contain assumptions that do not survive scrutiny.
What is a late-stage review mechanism?
A clause in the section 106 agreement requiring the appraisal to be re-run at a defined point before final sales, comparing outturn values and costs against the original assumptions and sharing any surplus, usually capped at the full policy requirement. Define the trigger, the formula and the dispute resolution route in the agreement itself.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.