Replacement dwellings within the greenbelt are a permitted exception under both national and local planning policies. According to national planning policy, “the replacement of a building, as long as the new structure serves the same purpose and is not significantly larger than the one it replaces”.

Each local planning authority has its own criteria for determining what constitutes “materially larger” when evaluating greenbelt replacement dwellings. These criteria, typically range from 5% to 35% of the existing dwelling or structures on the site, this can sometimes increase to 50% within a ribbon development. While neither national nor local policies provide a clear definition “materially larger,” numerous approvals and appeals have established a general guideline for what is permissible.

When crafting a planning strategy, it’s essential to consider two different calculations. The size of home extensions within the Greenbelt is assessed based on the “original” house as it existed in 1948 (or upon its construction if post 1948), calculations for Greenbelt replacement dwellings focus on the “existing” built form on the site. By utilizing permitted development allowances and creating a "fallback" we can demonstrate very special circumstances which can  lead to an approval for homes that are deemed to be materially larger."

Typically, the requests we receive for greenbelt replacement dwellings aim to design a home that maximizes size, and WhiteBox Architecture has a strong history of successfully designing and justifying homes that are significantly larger than those they replace.