Below the Ground Structures… and Why You Need Yours Surveyed
Below the ground structures, or underground structures, are part of many buildings, and should be carefully surveyed
Article By: Tom Ayre
Last Update: July 2019
What are Below the Ground Structures?
Below the ground structures, also known as underground structures, are literally the parts of a building that’s underground! Think basements, tunnels, pipelines, underground carparks and lift pits. Underground structures require slightly different planning than above the ground structures because there can be dangerous ramifications of working underground and moving soil around.
Why You Need to Survey Your Below the Ground Structure Before Starting Construction Work
Below the ground structures require careful planning and attention, so it’s important to undertake a survey of the area to understand the lie of the land. When beginning works on a below the ground structure, you must adhere to the BS 8102:2009 regulation. It’s there to give you advice and guidance on preventing any water from entering your structure. Waterproofing the area surrounding the structure is crucial because construction work needs to take place in a dry, safe environment.
It can be extremely costly if important elements of your project are overlooked before construction starts. If you decide not to have a survey, you could run into serious, expensive problems around material costs, labour costs, planning permissions and health and safety law. The worst case scenario is that you could end up demolishing the whole site and starting again. It’s hard to overstate the importance of going through the necessary procedures to ensure you are getting it right the first time!
What a Good Below the Ground Survey Will Establish
An accurate survey allows you to create a precise plan of your construction site. It also helps you identify, and plan for, potential issues. A survey will show your property boundaries – not something to miscalculate! It also plays a part in finding out the level of the water table so you can be sure that the area won’t flood during or after construction.
Undertaking the Survey
A topographical survey can be very useful for establishing ground level differences. You can then use the information to work out external access, light and ventilation. Ground levels are especially significant if your land is on a slope, because differing ground levels will affect water levels, therefore impacting the amount of soil needing to be excavated in order to build a level structure.
Furthermore, you must identify any load-bearing walls and establish how wide trenches need to be. Trial holes will be dug around the site after your survey so you can decide the best to place for foundations.
Remember that the type of soil will have an impact on the building work! Undisturbed soil (soil that’s been in place for thousands of years) is ideal because your foundations and footings should be placed on solid ground. A good geological survey will include a soil test to give you an idea of what the foundations are like before you start any structural work in the area.
In terms of materials, concrete is the most popular material for building basements as it is economical and provides a strong foundation. You must use reinforced concrete for your structure, and a good survey will help you plan your material costs accurately.