Site Viability Assessment: How to Use Market Data to De-Risk Developments

What a Modern Site Viability Assessment Really Involves

A good viability assessment covers much more than construction costs and planning gain. It’s about testing whether a scheme makes commercial sense, now and into the future.

That means looking closely at:

• Buyer demand: Not just “Is there demand in the region?” but “Is there demand for this kind of home, in this postcode, at this price point?”
• Absorption rates: How quickly are similar homes selling nearby? What price points are they achieving, and how much discounting is happening?
• Affordability alignment: Can local buyers realistically access the homes being proposed, given income levels and lending conditions?

These inputs help developers avoid launching schemes that might technically be buildable but commercially underperform. The earlier you identify risks, the more flexibility you have to course-correct.

Why Standard Data Sets Aren’t Enough

Outdated or too-broad data is one of the biggest risks in a viability assessment. Borough-wide stats, historic averages, or national trends won’t reflect what’s happening in a specific micro-market today.

Take, for example, a London borough with rising average values. If a nearby scheme has recently launched with heavy incentives, that could distort perceived appetite. Without real-time insight into active sales and buyer behaviour, you risk basing a multimillion-pound decision on the wrong assumptions.

That’s why forward-thinking land and development teams are now layering in:

• Granular pricing and transaction data
• Live portal search and enquiry patterns
• Up-to-date affordability metrics by income band

It gives a far clearer picture of whether the site, product and pricing strategy will hold up when it hits the market.

The Development Appraisal Process: Foundations of Viability

A solid development appraisal is the starting point for any credible site viability assessment. It helps both developers and local planning authorities understand if a proposed development is financially realistic and aligns with local planning goals.

At the heart of the process is comparing the gross development value (the total sales or rental income the project could generate) against all development costs, from land value and build costs to fees, finance, and planning obligations like affordable housing contributions.

Running different development scenarios helps test how changes in cost, value, or policy demands affect viability. It’s a practical way to flag pressure points early and support clearer, more constructive conversations during the planning application process.

For developers, it means fewer surprises. For planners, it offers confidence that the scheme can deliver what’s promised, without putting its viability at risk.

What Market Data to Prioritise in Your Viability Checks

Before advancing a scheme, developers are increasingly using local housing data to assess development viability, not just at the feasibility stage, but well before any planning application is submitted.

The goal? To ensure the site is both financially viable and aligned with real buyer demand in the area.

The most useful insight includes:

• Buyer demand signals: Use portal enquiry levels, search activity, and listing performance to gauge interest in comparable development sites or property developments nearby.
• Sales velocity and pricing evidence: Look at how quickly similar developments are selling, whether homes are transacting at guide price, and what level of financial contributions or incentives are being used to close deals.
• Affordability and income bands: Cross-reference your proposed unit mix and development value with local income data and typical loan-to-income ratios to see if pricing is within reach of target buyers.
• Pipeline competition: Check the local planning authority portal for approved and upcoming schemes. A crowded market may mean lower absorption and tighter margins. For a deeper look at how sales pace can impact site viability, read our insight into new build absorption rates.

Factoring in these metrics early in your site viability assessment helps de-risk the acquisition, support pre-application discussions, and build stronger viability evidence when it comes to planning.

How to Combine Market Insight with Planning Intelligence

The most viable sites aren’t just sellable, they’re also straightforward to get through planning. That’s why smart developers pair market data with early planning checks.

Start by aligning your proposal with the Local Plan and housing targets. If your site helps meet a known shortfall, whether that’s family homes or affordable units, you’re already ticking a key box. For more on evidencing this clearly, explore our guide to housing need data for planning applications.

Next, review past refusals nearby. Local planning history can highlight red flags and help you avoid repeat mistakes.

Look out for risk factors like flood zones, protected views or restrictive covenants. These can all affect site value and viability.

Finally, involve a planning consultant early. They can shape a narrative that combines local demand, pricing insight and policy compliance, helping smooth the path from land deal to planning approval.

The Benefits of Data-Led Site Selection

Viability assessments are ultimately about reducing risk and improving certainty. Market data helps land teams make faster, more informed calls on which sites to progress, redesign, or walk away from.

Here’s how developers are seeing the benefits:

• Fewer surprises post-acquisition: With a clearer understanding of demand and pricing limits.
• Improved internal confidence: Better alignment between land, planning, and sales functions.
• Easier external backing: Lenders and investors are more comfortable funding schemes with transparent evidence behind them.
• Faster go/no-go decisions: Avoiding months of wasted work on sites that were never commercially viable to begin with.

In a more cautious market, every advantage counts. Data helps you move decisively and defend your position throughout the development lifecycle.

Tools That Support Viability Assessments

Manual spreadsheets and static PDFs no longer cut it. Developers now rely on dedicated tools to build and test their viability assumptions with confidence. Key resources include:

• Hometrack Housing Market Intelligence
  Get postcode-level pricing, demand, and affordability data updated in real time, all in one platform.
• Viability and pricing modelling tools
  Test scenarios across different pricing levels, unit mixes, and cost bases to identify pressure points before you commit.
• Local planning data portals
  See what’s in the pipeline and how your proposal fits with existing and emerging policy constraints.
• Real-time listings and transaction data
  Benchmark against what’s currently on sale, and what’s actually selling, to make informed calls on pricing. You can also check live listings in your target area directly via platforms like Zoopla to benchmark local pricing trends.

By using the right tools, land and development teams can test their ideas early, refine proposals fast, and de-risk decisions before they snowball into cost.

Final Thoughts: Stronger Viability Starts with Better Data

Site viability isn’t just a one-time check, it’s an ongoing process that underpins the success of any development. And in 2025’s more selective market, it’s no longer just about feasibility, but about confidence.

Developers using postcode-level housing data are finding better sites, designing smarter schemes, and securing faster support from funders and planners alike.

Ready to strengthen your next viability assessment? Hometrack’s housing market insight helps developers reduce risk, move faster, and build with confidence.

Get in touch to learn how we can support your next land deal.