Why Every Local Authority Needs to Understand Development Appraisals in 2026

For most of the last two decades, social housing development sat firmly with housing associations. Local authorities commissioned, enabled and negotiated; but rarely built. That picture has changed. With the launch of the £39 billion Social and Affordable Homes Programme (SAHP) 2026–2036, the government’s Council Housebuilding Skills & Capacity Programme, and a renewed political appetite for council-led delivery, more authorities are stepping back into the developer’s chair. Bidding for SAHP opened in February 2026, with at least 60% of grant-funded homes expected to be for Social Rent. 

But here is the point that often gets missed: even where the authority is not taking development risk, a working grasp of financial viability is now indispensable. The reforms to the section 106 system, the new rent regime and the long-run grant settlement have all moved viability from a back-office calculation to a front-line policy tool. 

Below are five situations where development appraisal capability is no longer optional for councils, and what has changed in 2026 that makes each one more pressing.

Understanding the level of subsidy the scheme actually needs

Grant is rarely a round number on a spreadsheet. The required subsidy depends on land value, build cost inflation, the Future Homes Standard, the mix of tenures, the rent achievable under the 2026 Rent Standard (CPI+1% for existing tenants in 2026–27, with the rent flexibility cap), and the cost of meeting building safety and decarbonisation obligations.

A council that can read an appraisal can challenge a registered provider’s grant ask, identify where cross-subsidy is being assumed and spot where assumptions on sales values or void periods are doing the heavy lifting. Without that skill, the conversation defaults to whatever the provider’s finance team puts on the table.

Option appraisals for existing estates

Before any developer or registered provider is brought to the table, the authority needs its own honest view of what regeneration or refurbishment can deliver. Appraisals should test the impact of meeting social housing objectives, the cross-subsidy effect of any private-sector or market-sale element, and the consequences of different tenure mixes. The new SAHP allows additionality to be assessed across a portfolio of sites rather than scheme by scheme for regeneration, which gives more flexibility, but only if the council has done the underlying maths to understand which schemes carry the cross-subsidy and which lean on it. Going to the market with an undeliverable brief is the fastest way to lose two years and a reputation.

Proving viability when the authority is the developer

For councils bidding through SAHP’s Continuous Market Engagement route, or working in a Strategic Partnership with registered providers, viability evidence is no longer a private internal matter; it sits at the heart of the grant case.

Homes England and the Greater London Authority will assess bids on value for money, strategic fit and deliverability. Authorities without a Housing Revenue Account now have greater flexibility to deliver, and the National Housing Bank’s £2.5 billion low-interest loan facility (0.1% interest, 25-year duration) is available to support registered providers. Accessing any of this requires appraisals that stand up to external scrutiny. 

Assessing the grant implications of your housing needs policy

Housing policies have a financial dimension that is not always obvious. Different dwelling types: by size, tenure, location, supported housing designation and energy standard, require very different levels of subsidy to deliver.

The relationship is not linear: a larger home does not automatically need proportionally more grant, and a supported housing unit may need substantially more than a standard family home of the same floor area.

With the new statutory duty to publish a Local Supported Housing Strategy under the Supported Housing (Regulatory Oversight) Act 2023, authorities increasingly need to translate need into deliverable, costed pipelines. That translation is an appraisal exercise.

 Negotiating affordable housing contributions on private development

This is where the 2026 reforms bite hardest. The government’s January 2026 Section 106 roadmap has reshaped the negotiation environment in three important ways:

• Plan-stage viability is now the centre of gravity. The revised NPPF and accompanying guidance push viability assessment up the chain into local plan preparation. Site-specific viability assessment at the application stage is being constrained, and is explicitly off the table for schemes subject to the green-belt “Golden Rules.” Authorities that have not embedded viability in their plan evidence base will find themselves negotiating from a weaker position.

• The Homes England Clearing Service changes the playbook on uncontracted units. Developers were required to upload uncontracted s106 affordable housing units to the Clearing Service by 1 June 2026 to qualify for the emergency tenure-renegotiation route. LPAs are encouraged to take a pragmatic, light-touch approach to assessing bids, but only against an evidence base that includes site-level viability, published commuted sums policies, grant rates and recent local s106 transaction data. None of that is available to officers who cannot read an appraisal.

• A standardised s106 template is on the way. Town Legal LLP has been appointed to draft it, with the aim of reducing the time and cost of negotiation. Standardisation will help — but only on the legal mechanics. The numbers inside the agreement will still need to be argued, and that argument is fundamentally a viability argument. 

A successful s106 negotiation typically resolves a three-way tension between the local planning authority, the developer and the registered provider or ALMO acquiring the homes. Each party has different objectives: the LPA wants policy compliance and tenure mix, the developer wants a deliverable scheme with predictable returns, the RP needs the units to underwrite their own business plan against rent caps and regulatory costs. A good appraisal sets out the position for each party rather than just one, and that is what allows the authority to broker rather than referee.

What this means in practice

Three things follow from all of this.

Viability is a plan-making competency now, not just a development management one

Authorities preparing or reviewing local plans should be commissioning whole-plan viability work that can withstand examination, and aligning it explicitly with SAHP grant assumptions and the 2026 Rent Standard.

In-house appraisal capability is becoming a strategic asset

The Council Housebuilding Skills & Capacity Programme has already supported 81 councils, and the Council Housebuilding Support Fund has allocated additional funding to councils developing SAHP bids. Authorities that build genuine internal expertise, even at a modest scale, will negotiate better, bid more competitively and avoid expensive surprises.

The choice is no longer whether to engage with viability

Whether the authority is delivering directly, regenerating an estate, setting policy or sitting across the table from a developer, viability is the common currency. Authorities that cannot read it, test it and challenge it will find that the conversation about social housing is being had without them, and in 2026, that is a conversation no council can afford to miss.