The fast track route for affordable housing in London

The fast track route for affordable housing in London lets a scheme avoid submitting a viability assessment, provided it offers at least 35 per cent affordable housing (50 per cent on public sector land and on industrial land being lost to other uses), meets the tenure split, and complies with the other relevant policies of the development plan. That is the bargain in the London Plan 2021 threshold approach under Policy H5: hit the threshold and the borough does not interrogate your residual land value. Fall below it and your accounts are on the table.

The choice is strategic rather than arithmetic. A scheme at 32 per cent does not simply lose three percentage points of affordable housing. It gains a viability assessment, a review mechanism, a longer determination period and an argument you may not win.

How the threshold approach works

The threshold approach applies to applications that include ten or more residential units. It puts the burden of proof the right way round. An applicant who meets the threshold is taken at their word on viability. An applicant who does not has to demonstrate, with an open book appraisal tested by the borough's own consultant, that the maximum reasonable amount of affordable housing is less than the threshold.

Boroughs measure the percentage by habitable rooms or by units, whichever produces the lower proportion of affordable housing, and the measure matters on schemes weighted towards small private flats and large affordable family homes. Check which basis the borough applies before you fix the mix.

Three points catch applicants out. The threshold is a floor rather than a target, so a borough with an adopted local plan requirement above 35 per cent can still ask for more. The affordable housing must meet the policy definition of affordable, rather than simply being discounted. And the route is only available where the scheme complies with the other relevant policies, which is where most fast track claims actually fail.

What the fast track route requires

Four conditions have to be satisfied together.

1. The scheme provides at least the applicable threshold level of affordable housing on site, without public subsidy.
2. The tenure split follows the London Plan requirement, or whatever split the borough has adopted in its own plan.
3. The scheme meets the other relevant policies in the development plan, taken as a whole.
4. The scheme demonstrates it has sought grant funding to increase the affordable offer where that is available.

Condition three does the damage. A fast track claim is not a standalone concession, and an officer who finds the scheme falls short on daylight to neighbours, on play space, on fire safety information or on carbon reduction can refuse the fast track and ask for viability information as well. Design led capacity work matters here, because a scheme pushed past what the site can take on amenity grounds will fail condition three even at 40 per cent affordable housing. We set out that reasoning in the design led approach to optimising site capacity.

The practical lesson is to audit compliance before you commit to the route. Check the daylight and sunlight position against BRE 209, the play space provision against the GLA child yield calculator, the energy hierarchy, the whole life carbon position, and the fire safety submission. On a scheme of ten or more units, the Play Space Assessment is one of the least costly documents to get right and one of the more common reasons a fast track claim is queried.

Tenure split and what boroughs expect

The London Plan sets a split of at least 30 per cent low cost rented homes, at least 30 per cent intermediate homes, and the remaining 40 per cent determined by the borough according to local need. Low cost rent means social rent or London Affordable Rent. Intermediate means products such as London Living Rent and shared ownership, within the Plan's affordability caps.

Boroughs vary in how they use the flexible 40 per cent. Many direct it to rented homes, some to family sized intermediate units. Ask early and in writing, because moving tenure late in a scheme changes the appraisal, the section 106 drafting and the registered provider's offer.

Unit mix is the other half of the conversation. A split that meets the percentage on habitable rooms while providing only one and two bedroom affordable flats will attract an objection about family housing, and the borough's housing officer usually writes that objection before the planning officer sees the file.

When a scheme falls into the viability tested route

Any scheme below the threshold, or one that cannot meet the other three conditions, goes down the viability tested route. That means a full financial viability assessment prepared in line with national planning practice guidance on viability and the RICS guidance, submitted on an open book basis, published by the borough, and reviewed by a consultant whose fee the applicant pays.

Expect the borough to test the benchmark land value against existing use value plus a premium rather than against what the applicant paid. A price agreed in a competitive bid does not set the benchmark. That is the single most common reason viability cases collapse.

Expect also to argue about profit, build cost inflation, sales values and the treatment of abnormal costs. On a site with genuine abnormals, such as a basement, contamination or a demolition with heritage constraints, evidence them properly rather than asserting them. A quantity surveyor's cost plan with measured quantities carries weight. A single line in a cash flow does not.

Early stage and late stage reviews

Schemes on the viability tested route attract review mechanisms secured in the section 106 agreement. There are two, and they do different jobs.

A fast track scheme avoids both, with one exception. Where a fast track scheme does not start within two years of the permission becoming implementable, the Plan expects an early stage review to apply, so the viability benefit is tied to actual delivery rather than to consent.

Surplus captured by a review is normally applied as a cash in lieu payment towards affordable housing, subject to a cap. Negotiate the cap, the profit level used in the review, and the definition of the trigger date with care, because those three numbers decide whether a review mechanism is a formality or a seven figure liability.

Public land and industrial land at 50 per cent

Two categories carry the higher 50 per cent threshold. Public sector land is the first, including land held by boroughs, the Greater London Authority and other public bodies, and the threshold can apply across a portfolio rather than site by site where an agreement is in place.

The second is industrial land where the proposal involves a net loss of industrial, storage or distribution capacity. That link between industrial release and a higher affordable housing threshold is deliberate, and it sits alongside the no net loss policies that apply in Strategically Important Locations. We work through how those designations bite in industrial land in London and the no net loss policy.

Sites within an opportunity area may face further expectations set out in an area framework, including infrastructure contributions that interact with the viability position. Our note on what an opportunity area allocation changes covers that overlap.

Choosing a route, and what it costs you

Run the comparison before the design is fixed. The fast track saves the cost of a viability assessment and the borough's review fee, removes the review mechanisms, shortens determination and takes away the most contested part of the committee report. Against that, you are giving up units.

A rough decision sequence that works in practice:

1. Establish the applicable threshold, 35 or 50 per cent, and the measurement basis the borough uses.
2. Test the scheme at the threshold with your own appraisal, before any negotiation.
3. Audit compliance with the other relevant policies and price the gap.
4. If the gap to the threshold is within the likely cost of the viability route plus the expected review liability, take the fast track.
5. If it is not, build the viability case properly from the outset, with a cost plan and benchmark land value evidence.

One honest uncertainty. The London Plan 2021 remains the adopted strategic plan at the time of writing, and the Mayor has powers to review it. Check the current version of Policy H5 and the associated guidance on the Greater London Authority website before you rely on a threshold figure, and confirm the borough's own adopted requirement, which may be higher.

Browse the PlanScope report types to see which supporting documents a London residential scheme of this scale typically needs.

This is general guidance rather than legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.