Close this search box.
Close this search box.

Guillaume Rosaz



Guillaume Rosaz is a partner at Accuracy. Guillaume provides expert advice on large capital projects worldwide. Since 2009, he has supported owners, contractors, subcontractors and manufacturers on multiple international megaprojects in America, Europe, Africa, the Middle East and Asia.

Guillaume is an industrial engineer with a background in project control. He is an experienced construction management professional, having worked for an oil and gas contractor before joining Accuracy in 2016.

Guillaume works in a variety of sectors, including infrastructure, energy, chemicals, transport and various manufacturing industries.

Guillaume speaks French, English and Spanish.


  • Diplôme d’ingénieur, Grenoble INP Génie Industriel, France

In-depth expertise

Guillaume has been appointed and testified as an independent delay expert in international arbitration proceedings. He regularly provides written and oral testimony. He also supportsvarious project stakeholders in the context of amicable dispute resolutions.

Guillaume conducts project advisory engagements for his clients in the following contexts:

  • At tender stage / early project stage: project structuring, independent review of technical commercial offers, baseline definitions (schedule / cost)
  • During project execution: “cold-eye” reviews such as independent assessment of schedules or budgets, preparation of bespoke quantitative risk analyses on complex cost and time models, development of claim management strategy
  • Support in project-related financial aspects such as transfer price analyses or intellectual property valuations

Example of engagements


  • Appointed delay expert witness on behalf of the project owner on a $100m real estate complex – North Africa
  • Appointed delay and quantum expert witness on behalf of the EPC contractor on an $800m nuclear project – Europe
  • Provided independent delay and disruption expert advice for the EPC contractor on a $500m cable-stayed bridge – Central America
  • Provided independent delay and disruption expert advice for the EPC contractor on a $1bn refinery revamping – North Africa
  • Provided independent delay and disruption advice in the context of amicable dispute resolution processes or mediation for various road or highway concessionaires or contractors – Europe, Africa and Asia
  • Provided independent delay and quantum expert opinions on the robustness of various claims before initiating formal dispute proceedings in a number of sectors and locations
  • Defined claim strategy for the rolling stock manufacturer prior to initiating a negotiation process – a number of projects in Europe

Advisory / Decision-making

  • Provided an independent opinion on a technical commercial offer of the EPC contractor on a multi-billion-dollar nuclear complex – Asia
  • Performed an operational and financial audit of the project portfolio of a precast concrete manufacturer: action plan definition and implementation to restore the targeted operating margin – Europe
  • Provided an independent opinion to an EPC contractor regarding the schedule and cost implications that might be induced by the signing of an amendment proposed by an airport owner – America