NEC ECC: Defiinition of 'breach' or 'non performance'

Grateful if someone could clarify for me, from a legal perspective, would a Defect under NEC3 constitute an event of ‘breach, default or non-performance’ under the contract?

I am not a lawyer, but here goes …

It could be, BUT the procedures for correcting a defect are stated in the contract in NEC3 ECC clause 43. Further, the remedy if the Contractor does not correct a Defects within its defects correction period is stated in clause 45.1.

So, without knowing the context of why you ask this question, I would suggest that the first port of call if there is a Defect is to follow the contract, rather than resort to common law legal remedies.