When does a planning application need a topographical survey?
National rules ask for a location plan and a site plan, but most local validation lists go further. Where levels change across a site, planners usually expect existing and proposed site levels or sections, and many authorities ask for them on any new building. In practice, almost every new-build, extension on a sloping plot, or change to ground levels starts with a topographical survey.
Flood risk assessments
Sites in Flood Zones 2 and 3, and larger sites in Flood Zone 1, need a flood risk assessment. That relies on accurate ground, threshold and floor levels to Ordnance Datum. In Sussex and Surrey this comes up often: the coastal plain around Chichester, Worthing and Shoreham, and the flood plains of the Arun, Adur, Wey, Mole and Blackwater.
Trees, heritage and neighbours
- Trees: a BS5837 tree survey needs accurate tree positions, stem diameters and canopy spreads – we pick these up on the topographical survey.
- Conservation areas and listed buildings: historic centres such as Chichester, Horsham, Guildford, Reigate and Farnham need street elevations, frontages and roofscapes.
- Neighbours: windows, eaves and ridge heights of neighbouring buildings let your architect show daylight and overlooking impacts.
Protected landscapes and the Green Belt
Large parts of both counties are protected. The South Downs National Park has its own planning authority, and the Surrey Hills and High Weald National Landscapes and the Metropolitan Green Belt cover much of the rest. Here planners pay close attention to existing buildings, footprints, heights and volumes, landscape features and views, so the survey needs to record them accurately. Around Woking and Camberley, the Thames Basin Heaths affect residential schemes and SANG proposals, which also start with an accurate survey of the land.
What the survey should show
- Spot levels and contours to Ordnance Datum, on OS National Grid
- Boundaries, buildings, walls, fences and hard surfaces
- Trees with stem diameters, canopy spreads and heights
- Covers with cover levels, and watercourses with bed and bank levels
- Neighbouring building heights and street elevations where needed
- Buried services and drainage if the design depends on them
After planning: Building Regulations and setting out
The same survey control can be used for detailed design, Building Regulations drawings, setting out and as-built surveys, so it pays to get the survey right at the start.
Need a survey in Sussex or Surrey? Call 0345 548 5451 or email us with your site plan for a fixed quote.
