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What is a Ground Investigation Report?

Oct 16, 2022

Thank you for clicking on today’s Property Surveying blog post.  In this week’s instalment of our informative property blog, we are going to be taking a look at soil, or ground investigation reports. 

In particular, we are going to be focussing on what they are? When they are needed? The information they will provide.

Ground or soil investigation reports are required when a property owner is planning on undertaking construction works to their property.

In the majority of cases they won’t be required, as the architect or engineer will have a good understanding of the type of soil in the area.  This understanding thereby facilitating sound and considered design.

However, there are instances when engineers or architects may need additional information in respect of the type of ground that the planned works are being built on.

This is likely to be relevant when the property itself has had some form of issue during the course of its life.

These issues could be:

History of Movement

History of movement to a property such as subsidence is a typical scenario whereby the designers will likely want some further input into the soil content. 

In particular they are going to want to know the nature of the soil, how granular it is.  Thereby aiding and facilitating understanding and efficiency of structural design.

Existence of Mature Trees

Another scenario whereby designers are likely to want further input comes by the way of mature trees in the close proximity to the planned works. 

Mature trees are going to have a significant effect and change on the soil content to the perimeter of the property and in particular are going to interact with any planned construction work.

If there are mature trees, or even a single mature tree, reality is as much of the tree that can be seen above ground, will be below ground.  The root structure of the tree is likely to extend far and wide, this could dramatically change the manner in which foundations need to be dug or filled thereby resulting in the need for a ground/soil investigation report.

Sloped Ground or Unlevel Ground

Another scenario when a ground or soil investigation is likely to be required is the property resting on a slope, or being on unlevel ground. 

This can change the way in which the water drains away from the property, often resulting in the ground being softer than average.

This is going to affect the way in which conventional foundations would interact with the ground, therefore it is likely the designers are going to want input into the subterranean build-up so that they can fully design and take account for its fabric.

What is a Ground or Soil Investigation Report?

It is a relatively simple investigation.  It will see controlled bore holes drilled into the ground to the perimeter of the planned works.

These bore holes are likely to be many metres deep and significantly deeper than the proposed extension’s foundations. 

The aim behind these bore holes is to enable the operative to draw or excavate the soil from within the bore hole thereby specifically giving them a full understanding of what that soil does from the highest point at ground level, to the lowest point at the base of the bore hole. 

Once they have got this information to hand they will then be able to specifically update and advise the structural engineer and architect of this thereby ensuring that both of these designers can fully account for what needs to be done, often adjusting or changing planned works to account for the nature of the soil and ground.

In almost all normal circumstances, soil or ground investigation reports are unlikely to be required, however, as they do come with delay and cost, it is best for you to make enquiries with your design team at an earlier date to establish if they foresee the need for one. 

Generally speaking we are looking at bore holes and ground and soil investigation reports from a party wall perspective.  These are likely only going to be required if:

  • Basement works are taking place.
  • Extensive deep excavations are taking place.
  • Retaining walls are being built.

If you would like to discuss full ground investigation reports with our team of experienced building surveyors.  Or perhaps you would like to discuss party wall surveying with our team of experienced and qualified party wall surveyors, please feel free to give us a call today, or pop us an email, we will be more than happy to assist and advise you.

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