The ground
Alluvium · river gravel · chalk
The village centre is mapped on alluvium over chalk. Alluvium is river-laid clay, silt, sand and gravel, which the British Geological Survey describes as normally soft to firm and compressible. River gravel is mapped within half a kilometre.
Expect softer, slower-draining ground on the alluvium, and lighter, gravelly soil on the gravel. Ground can vary from one garden to the next, so neighbouring gardens may not behave the same way.
Planning
North Wessex Downs · Pangbourne Conservation Area
Pangbourne is in the North Wessex Downs National Landscape, and its centre is in the Pangbourne Conservation Area. Both count as designated land, so an outbuilding beside the house falls outside permitted development and needs planning permission, and outbuildings more than 20 metres from the house are limited to 10 square metres in total under permitted development.
In the conservation area, tree work needs six weeks’ notice to West Berkshire Council (small trees — under 75 mm in diameter at 1.5 m high — are exempt), and even taking down an existing fence, wall or gate might need permission. Across the river, Whitchurch-on-Thames and the Whitchurch Conservation Area come under South Oxfordshire District Council.