Topographical survey in London

Why online maps are not enough

A common starting point is Ordnance Survey MasterMap. It is excellent for locating a property, but its own specification states a nominal point accuracy, at its stated confidence level, of 1 m in urban areas and 2.5 m in rural areas.

A design that depends on a distance of a few centimetres to a boundary cannot be built on a source whose stated tolerance is a metre. The Sites Layer guide gives an absolute RMSE of 0.5 m for urban data, which is better, but still not survey grade.

Land Registry plans are weaker again for this purpose. Their guidance says the title plan shows general boundaries only, with no standard tolerance between the plotted line and the legal boundary.

When a council asks for one

There is no national requirement to submit a topographical survey. National guidance has no separate validation list beyond the national information, so a survey becomes mandatory only if the borough lists it among its local requirements.

Even then the council can insist on it only if the local list is formally adopted and was published on its website less than 2 years before your application. We check that date in our constraints check.

The London Plan does not itself demand a survey. It names topography as a site-context consideration, and the practical requirement comes from borough lists and officers who need levels to judge a scheme. Sloping sites, backland plots and anything with a level change to a neighbour are where an officer is most likely to need one.

When we recommend commissioning one anyway

Some jobs gain a great deal from a survey even when no council asks. A new dwelling at the end of a garden, a side or rear extension on a terrace with uneven ground, a basement, a new drive or a garden room near a boundary all depend on levels. Our new build drawings work usually begins by recommending one.

The same goes for a boundary dispute waiting to happen. A survey records what is on the ground today, with a date, which is better evidence than memory when a neighbour later challenges where a fence stood.

For the building itself, a measured building survey records internal rooms and the structure. Commissioning the two together means the house and the site sit on one datum.

Utilities and underground services

A standard topographical survey records what is visible: covers, gullies and valve boxes. It does not trace pipes and cables underground. For that, the industry standard is the BSI publicly available specification for utility surveys, which sets out four survey types, from a desktop study through site reconnaissance and electromagnetic detection to verification by exposing the service.

Each type builds on the last, and the desktop study is a prerequisite to the rest. For many house projects the first two are enough, but a deep excavation, a new drain connection or a basement may justify detection before design.

We tell you which level your site needs, and what it does and does not find, in the quote.

Standards, accuracy and what we show you

Survey quality is described by RICS guidance on measured surveys of land, buildings and utilities. The current edition introduces accuracy bands, and the guidance is published free of charge by RICS. A good survey states the band it was made to, so you and the council know how far to trust each figure.

That is the test of a good survey sheet: the scale, datum, date, band and legend are on the drawing, not implied. We will not take a drawing forward without them.

Because a survey is only as good as the checking behind it, our independent review applies here too: a second chartered technologist, never the person who prepared the drawing, checks the sheet before it feeds a design.

Price and next step

A topographical survey has no list price, because plot size, vegetation and access change the work. You receive a fixed quote after a free constraints check, and it covers the survey sheet and a DWG file for your design team.

Send us the address and a note of what you are planning. We will say whether a survey is needed for planning, advisable for design, or unnecessary for your scheme. For the planning side, see our planning drawings and location and block plans.