Which type of compensation event is applicable to the following situation?

We are under a NEC3 PSC contract with the Client (the contractor), and we are conducting CAT 3 checks of the design developed by a third party (the main designer of the project). The information that we need to start the check are usually provided to us by the third party (the Designer) under the Client coordination. The Designer provided us with a first set of information (including drawings, plans, etc) however did not include important information regarding the properties of the materials to be used, as the material specifications had not yet been completed at the time. We, as CAT 3 checker, raised a EWN to the Client to let him know the implications of starting the check based on missing information, and the impact of receiving this information only at a later stage. The Client acknowledged and wanted us to start the checks based on assumptions which we listed and communicated in writing. Few months later we finally received material properties from the Designer, which differed from those we had assumed, meaning we had to reupdate the check (extra time/costs). Under which category of CEs does this event fall according to the list in clause 60.1?

This is a very broad question. It could be 60.1 (1), (2), (3), (4) or (5) depending on what the Scope says is to be provided, and by whom, and what the status of your programme is.

I would say that the response to the EWN should probably have been an instruction changing the Scope - i.e. to start the CAT3 and the parameters to be used, which would presumably have been covered by an Employer’s Assumption so you had recourse if that proved to be wrong.

Thank you, Andy. The main challenge is defining the Scope for us CAT3, given that the third party (the main Designer) are still developing the design while we are asked to start checking it. In response to your second point, after the EWN the Client formally approved for us to start the check based on those assumptions, and agreed that we would raise a CEN if additional drawings came in a later stage indicating different parameters from those assumed.