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Full Measured Building Survey: The Importance of a Full Measured Building Survey in Construction

Are you torn between commissioning a building survey by an architect or a 3D-laser-scan by a chartered surveyor? Perhaps you may not know the difference between the various types of surveys and how they could help. Before starting any project involving construction, a site survey is one of the crucial steps to consider before designing your new home or extension.

20 December 2023
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Eugene Kim

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The survey process involves measuring up the existing property so that you are fully aware of the site conditions. A measured survey will include important information such as dimensions, structural elements, mechanical and electrical points as well as any potential risks that may require attention for repair. 

Figure 1: A site plan created after a topographic survey to determine all spotheights, tree positions, contours and boundary conditions. This scheme is considered a very large site.

Why Do I Need a Site Survey?

In London, we see many examples of people using basic unsurveyed plans or copied property plans from estate agents. Typically for planning permission purposes, a survey is not a mandatory requirement! This can cause serious issues down the line and should be avoided if possible. An accurate and detailed survey means you will have access to all the information needed to inform the design process without any surprises along the way. Here are some of the reasons you should consider a professional surveyor:

1) Accuracy & Reliability

Surveys provide precise measurements and building information. You don’t want to go through the whole process only to find out your property does not fit the plot, and yes, that happens a lot! Mismeasurements during the construction stage have much more complex consequences than they do in the interim. 

2) Data & Site Investigation

The more data you gather prior to starting the process, the more certain you will be at the construction stages. This includes any restrictions, legal compliance with neighbours, large trees on site and opportunities for design.

3) Risk Factors

A site survey can also identify potential issues on site. Often when homeowners intend to build extensions, there is a fair amount of structural work needed. A survey can highlight which walls may be load-bearing and point out signs of subsidence such as cracking or poor soil conditions. This will allow architects to design and advise accordingly.

proposal image

Figure 2: An image of our proposal after the topographical survey had been completed.

Measured Survey vs. 3D Scan: Choosing the Right Method for Your Project

There are a plethora of different ways to survey a plot or property. The two most common survey methods used for residential properties in London include a 3D Scanner or a Portable Laser Measure. Let’s understand the key differences between the two.

Portable Laser Measure:

This method involves a handheld laser which is used by architects or surveyors to measure distances in a building. A laser is typically used for indoor spaces, as it can be quite weak in outside light. This kind of survey is generally suitable for small to medium size projects using simple geometry methods and measurements at the click of a button.


  • Quick and Efficient
  • Basic Equipment
  • Cost Effective


  • Human Error
  • Fragmented Data: Each measurement is done manually, so if you miss one, you have to return to the site to measure it.
  • Not ideal for capturing intricate spaces

3D Laser Scanning

This is considered the premium and preferred choice when it comes to residential and commercial surveys. A 3D scan is a fast and accurate way to capture data – it collects millions of little dots called a “point-cloud” which is ultimately stitched together and turned into a 3D model. This is performed by a machine and offers utmost precision and reliability when it comes to measuring spaces internally and externally


  • 99% accuracy 
  • Great at measuring basic and complex properties
  • Efficient 
  • Captures extensive data 


  • Generally higher costs than a measured survey
  • Large amounts of data to process
  • Requires special software to convert and store point-cloud data

Depending on your project, when choosing which type of survey you require, consider things such as scale, accuracy and budget. In our opinion, when it comes to extensions, especially new builds and large projects, a 3D Laser Survey will always be the superior option offering reliability and pinpoint precision without the worry of mismeasurements!


Figure: The final design and site plan after the topographic survey had been conducted.


What are the Cost of Site Surveys in London:

The cost of a site survey in London can vary, depending on factors such as scale of the site and the type of site survey you wish to go for. You can expect a simple survey to start from a few hundred pounds, conducted by a professional for simple schemes, whereas large, complex projects or commercial properties will often opt for a 3D Laser Scan by chartered surveyors which can reach into the thousands. Extension Architecture, in particular, offers two types of surveys, a Measured Survey (£400+VAT) and a 3D Laser Scan Survey £450+VAT and upwards). Our team of professionals will conduct a measured site survey, including internal measurements of the property, documentation and site photographs using a handheld laser. This is suitable for smaller schemes, however, if the project intends to build with us, we always feel more comfortable if a full 3D scan is conducted prior to construction so that all drawings and site dimensions can be verified by our builders.


The Impact of Site Surveys

A good survey acts as your compass at the start of a project, setting you on a good trajectory with all the information you need keeping you well informed. A bad survey on the other hand, or in some cases, no survey at all has several complications often resulting in poor design, unwanted compromises and costly construction delays. There is no doubt that a site survey is one of the most important investments you will make in your project. In comparison, a survey of a few hundred pounds upfront compared to a construction budget is minimal, and can save you time, money and headaches down the line. A site survey and all its benefits will prove to be invaluable to your project’s success beyond measure.

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Eugene Kim

Eugene Kim, Founder and Managing Director of Extension Architecture, has led the firm for over 14 years, consistently delivering quality solutions. His dedication has been key to the company's growth and success.

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