Camden Basement Impact Assessment (BIA)



Planning is a legal procedure to which standard questions are applied. Croft Structural + Civil has developed and continues to evolve its documents to ensure that they meet the Council’s planning requirements. For Camden our Basement Impact Assessment (BIA) closely follows the guidance noted in CPG4 introduced in early 2011 (Camden geological, hydrogeological and hydrological study).DP27 in the London Borough of Camden’s Planning is closely tied to CPG4. We have formulated the above documents into a concise document that covers the Camden’s requirements. There are numerous areas that are covered in our BIA. As the Council develops CPG4 and DP27 our BIAs are evolving. Since 2017 Camden have appointed checking engineers who are meticulous to a fault. Their fees are in the region of £3,500-£5,000, Croft have worked closely with their requirements and numerous planning applications have been granted.


Croft Structural + Civil provides a service and which covers:

  • Desk study and walk over survey; and
  • Site Inspection
  • Meeting with an engineer to discuss the needs of the projects and specific requirements
  • Walk over survey to determine what the requirements of the site are
  • Review of local trees (not a full arboricultarlist report, but one can be commissioned)
  • Review of adjacent buildings where access is available
  • Are there signs of subsidence locally
  • Soil Investigation
  • Arranging soil investigation report
  • Bore holes to confirm ground and water tables
  • Reports by a geotechnical engineer
  • Arranging Hydrology report

Desk Study - This forms the bulk of the BIA and will cover:
Screening stage;

  • This stage identifies any areas for concern that should be investigated further from Desk study and walk over survey

Scoping stage;

  • The issues of concern that should be assessed further from the screening stage

Impact Assessment Stage

  • Suggestions for monitoring during the works of neighbouring buildings
  • Are there slopes that may slip?
  • Are landslides a concern?
  • Are there signs of subsidence locally?
  • Is network rail or the underground nearby?
  • Are there listed buildings close to the site that may be affected?
  • Water Flow and Hydrology
  • Review of local water tables
  • Will the development affect London’s Main aquifer
  • Will drinking water supplies be affected
  • Local water course reviewed within 100m
  • Are we close to drift deposits – springs are likely to occur near changes in ground from sands to clays
  • Flood Risk Assessment
  • Review on flooding
  • Comment on whether the development may affect the Hampstead Heath Swimmers
  • Avoid Adversely Affecting drainage and Run off
  • Review of environment agency information
  • Loss of Open Space or Trees
  • Review of local trees, their location and the affect the basement may have
  • Arrange appointment of Arboricultarlist if many or impart trees are to be affected
  • Structural Schemes of internal layouts
  • Proposed use and loadings
  • Retaining wall designs
  • Anticipate deflections of retaining walls
  • Local Stability
  • Highway loadings
  • Ensure that the scheme “Maintains Structural Stability of the building & Neighbouring Properties”
  • Construction Process
  • Method statement on how the contractor should approach the work to safely complete the design
  • The initial temporary design details for the basement


The report will have various specialist inputs:

  • A Chartered Geologist CGeol will complete a report on the stability of the land and how the basement will affect the surrounding area.
  • A Chartered Hydro Geologist CGeol will complete a report on how the ground water will be affected by the new basement.
  • Chartered Civil Engineer MICE CEng will review the drainage design
  • Chartered Structural Engineer MIStructE CEng will consider the basement design and the works necessary. At Croft Structural + Civil we ensure that all suitably qualified professionals have been involved in the production of our Basement Impact Assessments (BIA’s) to meet current planning requirements as laid out in CPG4 and DP27.On reflection we have a good opinion on Camden Planning. They have not simply imposed further red tape (although it may appear so). Before implementing and publishing DP27 and CPG4 they undertook extensive research that resulted in the Arup’s report.