The 8th house is the house of death, sudden accidents, and deep occult mysteries. Ketu here is extremely volatile.
Dr. Sharma provides a terrifying Vastu warning for anyone with Ketu in the 8th house. Ketu is represented by dogs. The roof of the house represents the 12th house (or Rahu/Saturn depending on the context).
If a person with Ketu in the 8th house keeps a pet dog tied up on the roof of their house ("chhat pe kutta baandhna"), they are creating a deadly astrological short-circuit. Dr. Sharma warns that this specific action will trigger a sudden, life-threatening accident for the native's son, forcing them to call an ambulance ("bete ki ambulance ka prabandh kar de"). Never keep dogs on the roof.