Under the ECC (which I assume you are talking about) anything that is a valid compensation event under clause 60.1 is something that you can assess in terms of both time and cost. It therefore depends if it is something that is your risk or not as a Contractor rather than if it simply was something outside of your control. A supplier of materials that lets you down may well be out of your control but is in most instances still going to be your risk/liability.
Therefore you need to be notifying compensation events and then managing the quotation process. Have a good read of section 6 and if you have access to it the guidance notes for that section that further elaborate on the clauses and their intent. To demonstrate entitlement you also need a thorough up to date Accepted Programme fully compliant with 31.2/32.1 and also accepted under 31.3, which is another key aspect of the NEC3 contracts.