Affordable housing planning: what developers and landowners need to know

 

Affordable housing is not simply housing which happens to be cheaper than the open market. In planning it is a defined group of tenures for households whose needs are not adequately met by the market, and it is commonly secured through a planning obligation when new housing is approved.

The August 2026 National Planning Policy Framework gives affordable housing a prominent role. Development plans are expected to set clear requirements for the proportion and tenure mix of affordable homes, including Social Rent, while national decision-making policy HO8 says proposals should meet or exceed up-to-date plan requirements relevant to the location.

This guide explains when affordable housing can be required, how it is normally secured, when off-site provision or a payment may be acceptable, what happens on vacant-building and Green Belt schemes, and where viability fits into the argument.

 

 

What counts as affordable housing in planning?

 

The planning definition is contained in the NPPF glossary. It covers specified forms of affordable housing for people whose needs are not adequately served by the commercial housing market. The precise tenure matters because a home does not become affordable housing merely because it is sold or rented below a particular local asking price.

Local plans should assess the needs of households requiring affordable housing, including Social Rent, and then set the type and mix expected from development. The result can differ substantially between authorities, so the first practical step on any site is to read the current development plan rather than assume a national percentage.

 

When can affordable housing be required?

 

For ordinary residential development, national guidance says affordable-housing planning obligations should normally be sought from major development. In Designated Rural Areas a development plan can set a lower threshold. The exact percentage and tenure split is then normally set locally. Separate rules can also support rural exception sites where affordable housing is the reason development is allowed outside the normal housing strategy.

National policy therefore does not create one universal affordable-housing percentage for every site in England. It tells plans how to set requirements and tells decision-makers how to apply those up-to-date requirements.

If you are dealing with a legal agreement, see our guide to Section 106 planning obligations.

 

On-site provision and tenure mix

 

Policy HO8 says affordable housing should normally be provided on the development site. Off-site delivery on a nearby site may be justified where it would optimise the quality or quantity of affordable homes, while a cash payment can be justified where the approach contributes towards mixed and balanced communities. Neither should be treated as an automatic developer choice.

The headline affordable percentage is only half the story. HO5 expects local policies to set the type and mix required to meet need, including the minimum proportion of Social Rent on major development. A scheme can therefore offer the right total number but still conflict with policy because the tenure mix is wrong.

 

Vacant Building Credit

 

Where a proposal reuses or redevelops a qualifying vacant building, affordable-housing contributions can be reduced to reflect the gross floorspace of the existing building. The credit does not apply where the building has been abandoned, and HO8 also excludes major development on land within or released from the Green Belt from this route.

Our Vacant Building Credit guide explains the calculation and the important distinction between a building which is vacant and a planning use which has actually been abandoned.

 

Affordable housing and the Green Belt

 

The 2026 Framework expects higher affordable-housing requirements for major housing on land proposed to be released from the Green Belt or which may be approved within it. HO5 says the relevant plan requirement should be higher than the rate applying outside the Green Belt and should require at least 50% affordable housing unless that would make the development unviable when tested in accordance with national viability guidance.

That contribution does not itself make Green Belt development acceptable. The proposal still needs to satisfy the relevant Green Belt decision-making policy.

 

Can viability reduce the affordable housing?

 

Sometimes, but viability is not intended to be a routine second negotiation after land has been bought. Policy DM5 starts from the position that a proposal which accords with up-to-date contribution policies should be assumed viable.

A site-specific assessment may be justified where the development type or site characteristics are materially different from those tested at plan-making, where unexpected costs burden the site, or where circumstances have changed significantly. The price paid for land is not by itself a justification for failing to comply with policy.

 

How affordable housing is secured

 

Affordable housing is commonly secured through a Section 106 agreement. The agreement can deal with tenure, eligibility, nominations, transfer arrangements, timing, affordability controls and what happens if circumstances change.

On 25th August 2026 the Government published national Section 106 affordable-housing engagement guidance encouraging developers, councils and housing associations to engage early and transparently where delivery problems arise. It does not replace the legal agreement or development plan, but it is useful current guidance where schemes become stuck at the delivery stage.

 

Before submitting a housing application

 

• Check the current affordable-housing percentage and tenure mix
• Establish whether the proposal is major development or falls within a Designated Rural Area threshold
• Check whether the site is in or released from the Green Belt
• Identify qualifying vacant floorspace before relying on Vacant Building Credit
• Speak to likely registered providers early where on-site affordable housing is proposed
• Do not assume a high land purchase price will justify a viability reduction
• Allow time for the Section 106 agreement to be negotiated

There is also a new delivery angle to watch. The £39bn Affordable Housing Programme gives councils a much bigger role as housebuilders, partners and potential purchasers of affordable homes, including some Section 106 homes that are struggling to find a registered-provider buyer.

 

Relevant policy and guidance

 

• National Planning Policy Framework, August 2026 — particularly PM12, HO5, HO8 and DM5
• Planning Practice Guidance: planning obligations
• National Section 106 affordable housing engagement guidance

 

 

Other Housing Sections

 

 

Affordable Housing Planning Page Updated: 31st August 2026