Structural Engineers Basement Construction2023-11-06T16:00:43+00:00

Contacting a structural engineer needs to be one of your first steps when considering a basement, whether as a new build, extension or conversion

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Basements are increasing in popularity, and a common question is whether clients can have a basement. In this video Russell Wrapson explains the investigations needed to decide whether a basement is feasible or not.

New build basements have always been in demand for high-end developments, however basement extensions and conversions are becoming increasingly popular. They are an excellent way to increase space and add value to a property

They are inherently a difficult proposition and require a structural engineer to complete the necessary investigations to ensure your plan is feasible before you spend your budget on design. Even if you already have architectural drawings there will be certain questions that will need to be answered by a structural engineer before the design process can be completed and building work can begin.

example of basement in construction - structural engineer Birmingham

Several Steps Are Required

There are several steps that are involved to ensure that the ground beneath your building and the building’s foundations are strong enough for a basement extension dependent on whether you have a basement already or looking to create a new one, these include;

  • A Topographical Survey – whether a traditional excavation is possible and how the basement will fit onto your property.
  • Site investigations – these are used to assess ground conditions and establish your property’s geological sequence, the presence of groundwater and the strength of the soil.

Existing Structural Survey

We will also need to establish whether your building is able to have a basement extension. This is usually determined with a structural survey of the property establishing:

  • Whether there is evidence of heave or subsidence
  • If the foundations are competent enough to undergo the work required to extend downwards

Key Design Considerations

There are several regulations and standards that need to be met to ensure the completed works will be fit for everyday use such as;

  • Appointment of a CESSW registered specialist to advise on waterproofing
  • Drainage and Waste disposal
  • Ventilation points; if the basement is to be used for car parking this is key


Call us today to discuss your project on 01993 225085

Basement FAQs

Do I need planning permission for a basement?2023-03-10T17:28:15+00:00

If it is a new basement where major works are involved to excavate for a basement that will provide accommodation, will affect the appearance of the existing house, or will have a light well you will more than likely need planning permission. It is best to contact your local planning authority before you start any work.

Can I build a basement under an existing house?2023-03-10T17:24:11+00:00

Yes, it is possible to build a basement under an existing structure. You need to engage with a structural engineer at the earliest opportunity for them to complete a site visit to determine if it’s possible and the best method of construction. This will affect the budget of the project and therefore its feasibility.

How does access affect my basement?2023-03-10T17:21:31+00:00

You can not assume that your neighbours will give you access for diggers and trucks to remove waste when you’re digging a basement. If you are surrounded by trees and other buildings this will also hamper access. There are ways to overcome these issues, but you need to speak to a structural engineer and have a site survey completed to determine whether your basement is feasible and the best construction method.

What is long-term water monitoring for a basement?2023-03-10T17:17:39+00:00

A site investigation that measured the groundwater completed in December would typically find a different level if it were completed in July. Any basement design needs to consider the potential of water all year round, therefore long-term water monitoring will allow your basement to be designed for the monitored conditions rather than assuming a worst-case scenario.

Do I need long term water monitoring for my basement?2023-03-10T17:14:46+00:00

BS8102 says you must design a basement assuming for a full head of water, i.e. up to ground level. Long-term groundwater monitoring can demonstrate that a lower level is appropriate saving you money. This is why SWJ recommend that long-term groundwater monitoring is undertaken as it allows them to design for the actual ground conditions and not the assumed worst case.

What is ‘heave to counter uplift’ in a basement?2023-03-10T17:09:31+00:00

Uplift in basement design is where changes to the ground where you have dug your basement will push up ‘uplift’ your basement structure. Structural engineers complete site investigations to calculate what weight of structure (and how it is built) will be needed to counter movement caused by ground water (hydrostatic uplift) or by the removal of the soil to build the basement (Heave due to removal of overburden pressure).

What surveys do I need for a basement?2023-03-10T17:07:52+00:00

You need a topographical survey and a site investigation (or ground investigation). These two reports combined will help in the process of applying for planning permission, and designing around existing natural and manmade features and utilities and will inform your structural engineers on the best construction method for your basement. Failure to have these reports completed could lead to expensive problems with your project and even its complete failure.

Do I need a site investigation for a basement?2023-03-10T17:05:33+00:00

Yes, a site investigation will inform your structural engineers on the best way to design your basement so that it can be built safely, be watertight, and structurally sound. Site investigations include the geology, water levels, and location (for access to excavate) of your proposed basement. You will also require a topographical survey.

Do I need a topographical survey for a basement?2023-03-10T17:03:13+00:00

Yes, a topographical survey provides information on existing natural and manmade structures including utilities and road furniture that could affect your development. You will also need a site investigation to determine ground conditions and water levels.

Read our blog – What’s the difference between a site investigation and a topographical survey.

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