What is a topographical survey?
A topographical survey creates an accurate, detailed map of a site and serves as the starting point for all the other site investigation surveys.
The survey measures and identifies:
Elevation and surfaces
Any buildings or structures
Natural features, such as trees, streams or vegetation
Street furniture
Relevant features on adjacent sites
This creates the foundation for a project’s design. The survey reduces the risks of abortive costs – costs incurred from mistakes or work that has to be redone – by giving designers and engineers all the relevant site constraints they have to work with.
Crucially, a topographical survey also forms the basis of other surveys. For example, a utility surveyor will ask for a topographical survey in order to plot the exact location of any pipes or cables on-site.
The only site investigation checklist you need
Download our site investigation checklist, which covers the 13 site investigation surveys you need to complete on every site. This includes a rundown of why you need each of them and at what stage throughout the project lifecycle.
The only site investigation checklist you need
Download our site investigation checklist, which covers the 13 site investigation surveys you need to complete on every site. This includes a rundown of why you need each of them and at what stage throughout the project lifecycle.
What happens if you get this wrong?
An accurate topographical survey is essential to development because any mistakes will result in problems down the line. This could mean abortive costs, for example in development redesigns if site boundaries or levels are recorded incorrectly.
Inaccuracies could also lead to problems with the finished building if development goes ahead. This happens all the time. Take a look at this Sainsbury’s in East London.
The topo survey was not done correctly and as a result, the building was constructed lower than it should have been. To compensate for this, the developers had to make the pavement slope down to the entrance, creating an uneven surface. Can you spot it?
This seems minor but it affects water drainage and the structural integrity of the building in the future.
When is a topographical survey needed?
For developments, the short answer is: immediately. A topographical survey should be the first thing you do when you decide to progress with a site. (Planning policy or legal searches take precedence if you’re simply thinking about buying a site, but topographical surveys are more important if you are committed to starting the development.)
Why do you need a topographical survey?
It enables all the other surveys to be done properly and allows architects and engineers to start designing the project accurately. By doing so, you remove surprises that could stop or add costly changes to your development down the line.
What is included in a topographical survey?
A topographical survey should plot the following:
The full extent of the site
Adjoining and adjacent curbs
Basic elevation of current buildings
Any hardstanding and green spaces
Drainage manholes
Height of boundary fences
Trees
Elevations of surrounding buildings
Surrounding building elevations are optional. However, we recommend that developers include them in the survey because architects can use that information to understand views from neighbouring buildings for planning purposes.
The finished report should produce a PDF and digital site plan in DWG format, which can be read and edited by CAD (computer-aided design) software. Other surveyors can then use that file to plot their own findings – such as trees or utilities – thereby keeping all the necessary information in one place.
Did you know?
Every height measurement in the UK is based on a small building on the Cornish coast? The Newlyn Tidal Observatory spent six years from 1915-1921 recording tide levels, thereby calculating the mean sea level and becoming the starting point for recording the height of any location in the UK.
That point is called Ordnance Datum Newlyn, and any topographical survey will record a site’s elevation relative to that height. Back in the day the whole of the UK was surveyed with manual level equipment which was limited by the distance of your eyesight. Checkpoints were marked across the UK so that surveyors didn’t have to go all the way to Cornwall. But nowadays we use GPS technology.
How long does it take to do a topographical survey?
This depends on several factors, such as the size of the site and number of surveyors sent to the site. However, most RenKap projects below 1ha take a single day to be surveyed and then a week to prepare and finalise the documents.
How do you find competent topographical surveyors?
Finding and qualifying surveyors has historically been a time-consuming process:
Find and shortlist suppliers.
Ensure suppliers are qualified – they will need to do a pre-qualification questionnaire (PQQ) to answer key questions such as:
Do they abide by the Construction, Design and Management Regulations 2015 and by the Health and Safety at Work etc. Act 1974?
Are they competent TSA (The Survey Association) members?
Do they have necessary insurance (professional indemnity, employer’s liability and public liability)?
Do they provide adequate quality control procedures?
Are they financially stable?
Do they have testimonials from other clients for similar work?
Create a scope of service – this will ensure the survey covers all the necessary areas and that the quotes you receive are on a like-for-like basis.
Undertake tendering and procurement – send out the instruction to tender (ITT) which will include site information, tender instructions, scopes of service and contracts. Review quotes and assess and select the right suppliers.
Draw up the paperwork and sign the contract.
How does RenKap simplify the site investigation process?
Watch our video to see how RenKap works
How does RenKap simplify the site investigation process?
Watch our video to see how RenKap works