Pre-Acquisition Due Diligence: What Developers Should Check

5 June 2026 · 5 min read · Development

The decision to acquire a development site is the single largest financial commitment in the development lifecycle. By the time the purchase completes, 70% of the project's total cost has already been determined by the site's characteristics, planning parameters, and physical constraints — even though no design work has been done. Pre-acquisition due diligence is not a box-ticking exercise; it's the process that determines whether the scheme will make money or lose it.

The Five Pillars of Due Diligence

Thorough pre-acquisition due diligence covers five interconnected areas. Weakness in any one can turn a viable scheme into a loss-maker.

1. Planning and Legal

• Planning status — is there an existing consent, an outline consent, or is the site allocated but unconsented? What's the realistic density and unit mix achievable?
• Section 106 and CIL — what obligations are attached or likely? Affordable housing requirements, education contributions, transport contributions. These can run to £50–150/m².
• Building Safety Levy — from October 2026, qualifying residential developments face up to £100/m² GIA. Is the site captured?
• Restrictive covenants and rights of light — neighbourly constraints that can reduce achievable massing. Check early, not at Stage 3.
• Land Registry and title — easements, wayleaves, access rights, and any unusual title restrictions.

2. Ground Conditions and Environment

• Geotechnical desk study — published geological data, borehole records from nearby sites, known ground risk profiles. On brownfield sites, budget for intrusive investigation.
• Contamination assessment — Phase 1 desk study (historical land use) and Phase 2 site investigation if warranted. Remediation costs on contaminated land can exceed £500,000 on a one-acre site.
• Flood risk — Environment Agency flood zone classification. Surface water drainage constraints are increasingly a planning blocker, not just a design challenge.
• Utilities infrastructure — location of existing services, capacity for new connections, diversion costs. A high-pressure gas main or Thames Water sewer crossing the site can fundamentally affect developable area.

Abnormal ground conditions are the most common cause of development appraisals being wrong by 10–15%. On brownfield sites, we recommend budgeting a contingency of 10–15% for the ground works package alone, even after site investigation. The alternative — a flat 5% contingency — is optimism, not risk management.

3. Cost and Viability

• Order of Cost Estimate (NRM1) — a structured cost estimate based on floor area, function, and form, benchmarked against recent comparable schemes. Not a guess; a professional assessment.
• Trade-specific inflation modelling — if the scheme won't start construction for 18 months, what will costs look like at procurement? Apply trade-level inflation, not a flat percentage.
• Residual land valuation — work backwards from GDV, deducting construction cost, professional fees, finance, developer's profit, and contingency. The residual is what you can afford to pay for the land.
• Sensitivity testing — what happens to the residual if GDV drops 5% or costs rise 5%? If the residual goes negative, the site is marginal at best.

4. Market and Value

• Comparable sales evidence — recent transactions within 0.5 miles, adjusted for size, quality, and time. Don't rely on asking prices.
• Demand drivers — what's driving demand in the location? Employment growth, transport investment, school catchment areas, regeneration schemes.
• Supply pipeline — how many competing units are consented or under construction in the area? Oversupply suppresses values at exactly the wrong moment.
• Rent and yield assumptions — for commercial elements, check that rent and yield assumptions are evidence-based, not aspirational.

5. Programme and Deliverability

• Realistic programme — from acquisition to first revenue, including planning, design, procurement, and construction. Most development appraisals understate the programme by 3–6 months.
• Pre-letting or pre-sales requirement — if the funder requires pre-lets or pre-sales, factor the time and cost of achieving them into the programme.
• Construction access and logistics — can construction vehicles access the site? Are there traffic management constraints, noise limits, or working hour restrictions?
• Party Wall and neighbourly matters — adjacent owners, shared walls, basement extendibility. These can delay projects by months if not addressed early.

The Due Diligence Cost

Proper pre-acquisition due diligence costs money — typically £15,000–£50,000 depending on site complexity. This is insignificant against the land value and can save hundreds of thousands in unforeseen costs. The table below shows typical professional fees for pre-acquisition work:

• Cost consultant (OoCE + cost plan): £3,000–£8,000
• Geotechnical and environmental: £3,000–£10,000
• Planning consultant: £2,000–£5,000
• Structural engineer (feasibility): £2,000–£5,000
• Legal (planning and title review): £3,000–£10,000
• Valuation / appraisal: £2,000–£5,000

Sources: RICS New Rules of Measurement NRM1 (Order of Cost Estimating); RICS Red Book Global Standards; BCIS cost benchmarks (2026); MHCLG Building Safety Levy guidance (2026); Environment Agency flood risk data; NorthEight pre-acquisition portfolio data. This article is for general guidance only.