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Consulting Engineers

Are basements worth the risk?

A lot of you will be aware of the recent collapse of a £3.5million Georgian townhouse in Barnes during works to excavate a new basement. This has resulted in a lot of people questioning if constructing basements is still worth the risks.

My view is that they are worthwhile as long as they are done properly without anyone trying to take any shortcuts. A full professional team that is experienced in basement work should be appointed by the client. A brief checklist is given below that covers the main points to consider when doing a basement.

  • Appoint a full professional team experienced in basements including a fully qualified Architect, a Chartered Structural Engineer (as most Boroughs now insist on a Chartered Structural Engineer overseeing basement works) and the relevant party wall surveyors for the various parties involved.
  • Have a full and extensive soil investigation done with a fully interpretive report by a specialist geotechnical ground investigation company, which will give essential information such as type of soil, allowable ground bearing pressures to reduce the risk of settlement, water table levels etc.
  • Appoint a suitable qualified and experienced contractor to do the basement works. This is not the place to just accept the lowest tender price, as each tender should be thoroughly reviewed to ensure that all of the important aspects have been covered. This would include items such as a detailed temporary works method statement and design produced and checked by a suitably qualified Chartered Structural Engineer, a complete Health and Safety Plan, adequate resources and suitably qualified staff. It is also essential to get references of previous basements they have done and visit some of them if possible and speak to the previous clients to get an understanding of how they worked etc.
  • Check that all the Party Wall Awards will be in place 14 days prior to the intended start date, as works cannot commence until this is done.
  • Check that all of the necessary insurances are in place to protect the client’s, as well as the neighbours’ properties, as well as all of the Contractor’s insurances, including a non-negligence policy is in place. Check that all of the insurance companies have been notified prior to work commencing on site.
  • Ensure that all of the Planning or listed building consents are in place with the local authority before any work commences on site.

Basements are a good way of providing additional space, particularly where the property cannot be extended upwards due to Planning constraints. Basements also have excellent thermal properties which can help with reducing energy consumption for heating etc. and provide excellent accommodation for the modern family way of living. This is one of our specialist areas and we have worked with lots of Architects and developers on these type of projects, which are worth doing provided everyone understands the risks and takes steps to mitigate the risks during the design and construction stage, they can be constructed safely and add considerable value to the property.

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