Section 106 & Affordable Housing: A Developer's Finance Guide

Section 106 of the Town and Country Planning Act 1990 allows local planning authorities to require developers to enter into legal agreements as a condition of planning permission. These planning obligations typically require the developer to provide affordable housing, contribute to local infrastructure (schools, highways, open space), or mitigate the impact of the development on the local area.

For residential developments of 10 or more units (or sites of 0.5 hectares or more), affordable housing provision is almost always required. The proportion varies by local authority - typically 20-40% of units - and the tenure mix (social rent, affordable rent, shared ownership, First Homes) is specified in the local plan.

Section 106 obligations directly affect your development's financial viability because they reduce the number of units you can sell at full market value. Understanding how to model S106 costs accurately, and how lenders factor them into their assessment, is critical for any scheme of 10+ units.

Affordable housing units are transferred to a registered provider (housing association) at a discounted price - typically 40-60% of market value for social/affordable rent and 60-70% for shared ownership. This discount directly reduces your scheme's GDV. A 30% affordable housing requirement on a 20-unit scheme means 6 units sell at 40-60% of market value, significantly impacting total revenue.

Worked example: A 20-unit scheme with an average market value of £300,000 per unit has a full GDV of £6M. With 30% affordable housing (6 units at 50% of market value), the effective GDV drops to £5.1M. That £900K reduction flows directly through to your profit calculation and affects how much a lender will advance.

Infrastructure contributions (education, highways, open space) are typically fixed sums specified in the S106 agreement. These are additional costs in your development appraisal - not a GDV reduction - and are usually payable at specific trigger points (e.g., prior to occupation of the first unit, or before 50% of units are occupied).

Community Infrastructure Levy (CIL) is a separate charge applied in many local authority areas, calculated per sq m of new development. Unlike S106, CIL rates are non-negotiable and published in the local authority's charging schedule. Include CIL in your appraisal from the outset - it's not a surprise cost if you check the charging schedule early.

If the full affordable housing requirement makes your scheme unviable, you can submit a viability assessment to demonstrate that the S106 obligations should be reduced. This is a formal financial appraisal, typically prepared by a specialist surveyor, that shows the scheme cannot deliver a reasonable developer profit with the full affordable housing requirement.

Viability assessments are contentious. Local authorities are sceptical of developers claiming unviability, and they'll appoint their own assessor to scrutinise your inputs - land value, build costs, sales values, profit margin, and finance costs. The inputs must be transparent and defensible. Inflating costs or deflating revenues to manipulate the viability outcome will be challenged and can damage your relationship with the planning authority.

Acceptable developer profit margins in viability assessments are typically 15-20% of GDV for market housing and 6% of GDV for affordable housing. Finance costs should be modelled at current market rates with a realistic build programme. Land value is benchmarked against an 'existing use value plus premium' methodology - the value the land would achieve in its current use, plus a premium to incentivise release for development.

Successful viability negotiations often result in a reduced affordable housing percentage, a change in tenure mix (more shared ownership and fewer social rent units, which narrows the discount), or a phased trigger for affordable housing delivery. Some authorities accept commuted sums (a cash payment in lieu of on-site affordable units) for smaller schemes, which simplifies the development and improves lender appetite.

Development lenders factor S106 costs into their assessment in two ways: the affordable housing discount reduces the GDV they use to calculate leverage, and infrastructure contributions are added to the total development cost. Both reduce the loan amount the lender will offer.

GDV calculation: Lenders calculate GDV using blended values - market units at full value, affordable units at the discounted transfer price to the registered provider. If the S106 agreement isn't yet finalised, lenders will assume the full local plan requirement in their assessment, which may restrict your facility. Negotiating S106 terms before approaching lenders gives you a more accurate GDV to work with.

Affordable housing pre-sales: Some lenders require contracts with registered providers to be in place before they'll advance development finance for affordable units. This provides certainty on the affordable housing revenue but requires early engagement with housing associations. Having a registered provider letter of intent or development agreement in place strengthens your funding application significantly.

Trigger points: S106 payment triggers affect your cash flow modelling. If infrastructure payments are due before unit sales complete, your development finance facility needs to account for these outlays. Lenders will check that your facility covers all S106 payments as they fall due, and insufficient provision can cause funding gaps mid-project.

Registered provider forward funding: Some housing associations will forward-fund the affordable housing element of your scheme - effectively paying you during construction for units you'll deliver at completion. This injects cash during the build phase, reducing your development finance requirement and improving scheme viability.

Mezzanine to bridge the equity gap: S106 obligations increase your total development cost while reducing GDV, which means you need more equity to fund the difference. Mezzanine finance can fill this gap, stretching your leverage to 85-90% of total costs. The blended cost of senior debt plus mezzanine must still produce an acceptable profit margin, but for viable schemes, this structure works well.

Phased delivery: For larger schemes, negotiating a phased S106 delivery - where affordable units are delivered alongside or slightly behind market units - can improve early cash flow. This allows market unit sales to fund the affordable housing delivery, reducing peak debt and improving lender comfort.

Off-site contributions: Where local plan policy permits, a commuted sum payment in lieu of on-site affordable housing can simplify your development. You build and sell 100% market housing, and the commuted sum is modelled as a development cost. This is often more attractive to lenders because the entire scheme generates market GDV, and there's no need to coordinate with a registered provider during construction.

For developers exploring other funding options, we also arrange refurbishment finance and bridging loans. You may also find these guides useful: GDV vs Market Value Explained, Refurbishment Finance vs Development Finance, CIL & Section 106 Obligations. When comparing property finance options, consider the regulatory framework: the Financial Conduct Authority (FCA) regulates certain types of lending, while RICS standards govern valuations across all product types. HM Land Registry registration applies to all secured lending, and Building Regulations compliance affects the exit valuation regardless of which finance product you use.