Sub-Contractor Technical Interface Review (STIR)

Ensuring physical interfaces were allocated, coordinated and completed correctly first time on site by subcontractors during the London Bridge Station Redevelopment project

Technical design and assurance standards supported the design development process up to approved for construction status (AFC).

Early construction stages identified interface issues that arose between subcontractors’ packages. Best practice for technical assurance would be to engage sub-contractors at, or before, the interdisciplinary design coordination or review stages (IDC/IDR).

However, this does not always fit public sector procurement rules to get best value in major projects from tendering off a finalised accepted design. The outcome of this staged approach is that packages let separately could allow issues to arise between subcontractors. To address this, the subcontractor design management team on the London Bridge Station Redevelopment (LBSR) project developed the “Subcontractor Technical Interface Review” process – STIR.

Watch the above interview with Rupert Shingleton who discusses the continuous improvement of quality during delivery.

Implementing STIR

The STIR process was implemented in three stages:

STIR stage 1

Occurred at the start of the design process for the sub-contractor package. It enabled:

  • Capture lessons learnt from previous stages
  • Clarification of scope of works
  • Interface definition.

STIR stage 2

Occurred approximately six weeks into the design process, prior to design approval. It enabled:

  • Confirmation of incorporation of STIR I outputs
  • Coordination between interfacing subcontractors.

STIR stage 3

Occurred after approval of subcontractor design, prior to start of manufacture. The final stage enabled:

  • Review and confirmation of buildability and sequencing to meet programme
  • Confirmation that all paperwork was in place for design, quality and build.


Benefits to the LBSR project included:

  • Reduced physical scope gaps in the design that would later appear on site
  • Better understanding, and clear ownership, of physical interfaces on site by all parties
  • Incorporated lessons learnt from previous designs or site installations to bring efficiencies
  • Better collaboration and communication between all parties
  • Decreased costs and programme time from rework and potential health, safety and environment associated risks.

The STIR process also benefitted subcontractors in the following ways:

  • Reduced design programme and therefore overall programme duration
  • Lower costs for additional reworks
  • Better understanding of work scopes and interfaces.

Recommendations for future projects or programmes

All project teams – design, commercial, planning, and delivery – benefitted from the STIR process. The key recommendations from the project team are to:

  • Ensure that the process aligns for all subcontractors, otherwise some will start and not have the relevant information from others that have not started
  • Ensure there is someone with responsibility for progressing each stage in the process
  • Assign an owner from each party to the process.


The case study was produced by Matthew Woolacott, Senior Design Manager, Costain, November 2018.

Further information
For more information on this Learning Legacy case study please email