unsound

/ʌnˈsaʊnd/
adjective
  1. Not in good condition; weak, damaged, or unhealthy.
    • The building's foundation was unsound, so they had to demolish it.
    • The bridge was declared unsound and closed to traffic.
    • He had to stop running because of an unsound knee.
  2. Not based on facts, good judgment, or reliable reasoning; faulty.
    • Her argument was unsound because it relied on outdated statistics.
    • The scientist argued that the theory was unsound.
    • Investing all your money in one company is an unsound financial decision.