Basement Impact Assessments

Land values remain very high in central London and also in many of the desirable suburbs. Space is therefore limited, with pressure to ensure that all developments maximise the potential opportunity. Utilisation of basements for new and refurbished developments is increasingly more common.


Basement development has been recognised as having an impact on local flooding, groundwater flow and quality and ground movements.  All these issues could impact on immediate neighbouring properties and possibly combined developments on larger geographical areas.


Local Authorities and the London Boroughs are increasing the range of potential issues that need to be assessed, including surface water, groundwater, flooding, drainage, archaeology, land stability and construction methodology.  Each of these areas often requires an accredited professional to undertake a Basement Impact Assessment (BIA).


Your Planning Application


When starting your application process it is important to confirm details with the relevant London Borough or Local Authority to ensure the BIA meets the requirements to achieve planning consent, with the minimum delay to your project;

  • Ask the planning officer for their exact requirements for the assessment (e.g. groundwater, surface water, land stability, archaeology, construction sequence etc.)
  • Confirm the professional qualifications needed to produce the assessment (e.g. Chartered Engineer / Chartered Geologist) – you may need to engage more than one company
  • Confirm the current relevant planning guidance for the assessment
  • Ask if a desk study will be sufficient and if any site investigation requirements may be conditioned


By making sure the Basement Impact Assessment only covers what the Local Authority requires it will save you time and unnecessary costs.


Our Experience


Our experienced staff include professionals Chartered with CIWEM and the Geological Society of London, who are able to assess surface water and groundwater issues to the standards required by the London Boroughs and Local Authorities.


Since 2010 there has been a steady increase in requests for BIAs and we have completed many assessments particularly in Camden, Tower Hamlets, Westminster, Dulwich, Merton, Hammersmith & Fulham and Kensington & Chelsea. We believe that other London Boroughs and wider Local Authorities will also be requesting BIAs as part of the planning approval process.


We have been working in the Thames Valley for over 15 years and have developed working relationships with many of the London Boroughs and Local Authorities and the Environment Agency as regulators and planning consultees. This experience ensures that our reports are best placed to gain approval quickly and efficiently.


We have also provided Expert Witness services acting for insurance companies when projects have not followed best practice.


Contact us for more information on how we can help with your basement development.