Engenica House Wraysbury Reservoir Coppermill Road TW19 5NW Data via plota.co.uk

Green belt policy allows a short list of exceptions, such as limited extensions and replacement buildings. Anything else needs very special circumstances that clearly outweigh the harm. Some green belt land can count as grey belt, where it does not strongly serve the green belt's purposes. The council decides this in its green belt assessment or on each application, so we do not mark it here.

The Environment Agency flood map for planning. Homes in zone 3 must also pass the sequential test. Surface water flooding is a separate map.

Where development of farmland is needed, policy prefers poorer land over the best and most versatile (grades 1, 2 and 3a). Three sources: Natural England's post-1988 field surveys, which are definitive where they exist; the Defra predictive map for England (2025) and the Welsh Government predictive map, modelled from the soil map with 3a and 3b split; and the 1970s provisional map, which planners and other services still show, coarser and with grade 3 undivided. Where the provisional and predicted grades disagree, treat the predicted grade as the current estimate and expect an application to carry its own survey.

Schemes that add traffic, parking or combustion plant are assessed against the area's action plan and may need an air quality assessment.

Harm to a protected site is only accepted where there is no alternative and an overriding public interest.

Sites of special scientific interest are the best wildlife and geological sites in the country. Development likely to harm one is rarely permitted.