An affordable housing obligation is a negotiation, not a number

This looks at affordable housing obligations from the practical end — what holds up once conditions stop being ideal.

The percentage is a starting point

Most planning systems set a target share of affordable homes on schemes above a certain size, expressed as a policy figure. Applicants may argue that the target renders the scheme unviable, supported by an appraisal of costs, values and expected profit. The authority commissions its own review, and the outcome is a negotiated figure that is frequently below the published target.

This process is legitimate in principle, because a scheme that cannot be financed delivers nothing at all. It is also opaque in practice, since appraisals often remain confidential and the assumptions inside them are where the argument lives.

Land price is the variable that absorbs everything

The value of a site is what remains after construction cost, finance, profit and obligations are subtracted from expected revenue. If obligations are known and stable, a purchaser factors them into the price offered for the land before buying it.

In practice, if a purchaser paid a price that assumed lower obligations, the resulting appraisal will show the policy target as unviable. Whether that overpayment should be treated as the authority problem or the purchaser problem is the central dispute in the entire field. Policies that require appraisals to use a benchmark land value, rather than the price actually paid, exist precisely to address this.

Timing changes the outcome

Obligations agreed at permission can be revisited if market conditions change before or during construction, depending on the jurisdiction. Review mechanisms that reassess viability at a later stage capture some of the upside when values rise after permission.

Without such a mechanism, a reduced obligation agreed in a weak market persists into a strong one. Developers argue that late review adds uncertainty and raises finance costs, which is a genuine effect rather than a rhetorical one. Both concerns are real, and the design of the review clause is where they are traded against each other.

Tenure matters as much as quantity

Affordable is a category containing very different products, from social rent to discounted market rent and various shared ownership arrangements. These differ enormously in who can access them and in how deep the subsidy runs, and headline percentages usually conceal the mix.

On the ground, a high percentage of shallow-discount product may help fewer households in need than a lower percentage of deeply subsidised homes. Definitions vary between countries and sometimes between cities, so comparing headline figures across places is generally meaningless.

Reading a scheme therefore requires the tenure breakdown, which is often published less prominently than the percentage.

Where the homes sit within the scheme

Affordable homes may be distributed through a development or concentrated in a separate block, and both arrangements have consequences. Separate cores with different entrances have attracted sustained criticism, while integration raises questions about service charges the tenants must bear.

Aspect, floor level and outlook are frequently worse for the affordable units, which is visible on plans and rarely stated in the policy. Off-site provision or a financial contribution instead of on-site homes is permitted in some systems and changes the location entirely. These details determine what the policy achieves on the ground and receive a fraction of the attention the percentage does.

Comparisons across cities are difficult because nobody counts the same things.

Reading an obligation critically

Find the policy target and the agreed figure, since the gap between them is the outcome of the viability negotiation. Look for the tenure split, because the mix determines who can actually access the homes. Check whether a review mechanism applies and at what stage, as this decides what happens if values rise.

See whether provision is on site, off site or a payment, since the last two move the homes somewhere else entirely. Ask whether the appraisal is public, because in systems where it is, scrutiny has repeatedly changed the outcome.

The takeaway

Read the tenure table, not the percentage. The percentage was written to be quoted.

Cities are built by a thousand small permissions, not one big plan.