Draft NPPF: Diverse Sites, Medium Development and the Risks of Mandating Percentages

Policy HO6 of the draft NPPF consultation seeks to strengthen support for small and medium-sized sites by requiring local plans to allocate land to accommodate at least 10% of housing on sites no larger than one hectare, and a further 10% on sites between 1 and 2.5 hectares.

The rationale is clear. Sites of between one and 2.5 hectares are typically delivered by SME housebuilders, tend to build out more quickly, and can make an important contribution to housing supply, particularly where larger strategic sites stall. In that sense, the proposal aligns with a long-standing policy objective to diversify delivery and reduce reliance on a small number of large schemes.

However, the introduction of a fixed percentage requirement raises more difficult questions. While diversity of sites is desirable, mandating that a specific proportion of housing must come from a defined size range risks prioritising numerical compliance over planning judgment. Local housing markets vary considerably, as do site availability, settlement patterns and environmental constraints. In some areas, opportunities for sites of between one and 2.5 hectares may be limited or poorly aligned with sustainable development objectives.

For plan-makers, this proposal adds a further layer of prescription at a time when plans are already expected to meet ambitious housing targets and demonstrate deliverability. The risk is that authorities feel compelled to allocate medium-sized sites to meet the percentage requirement, even where larger or smaller sites may be more appropriate in planning terms. This could lead to plans that are technically compliant but less coherent spatially.

For delivery, there is also a question of flexibility. SME builders benefit from certainty, but they also operate in diverse local markets. A rigid percentage approach may not respond well to changing market conditions over the life of a plan, particularly where viability, infrastructure or land supply issues emerge.

The key issue is not whether medium-sized sites should play a greater role in housing delivery, but whether that role is best secured through fixed national percentages. A more effective approach may lie in requiring authorities to demonstrate how their site allocations support a diverse delivery pipeline, rather than prescribing exactly how that diversity must be achieved.

Small and medium-sized housebuilders play a critical role in delivering homes quickly and diversifying supply