What amount requires repair

Does anyone know if there is a standard for determing how much termite damage to floor joists/girder/ban there can be until the need for repair/replace? For example, a floor joists can have 1/4 of the wood damaged, but still be structural.

Thanks,
Russell

Tough one for us to determine without destructive testing. You never know if there is a live infestation deeper inside the wood. Defer off to the Pest Applicator and let them do the destructive testing and estimates.