Drydocking Frequency
Standard 5-yearly cycle with one intermediate drydocking allowed up to 7.5 years for certain ship types under in-water survey schemes.
In practice
Operator coordinates the schedule with charterer and class. Drydock period includes routine UTM, hull repair, antifouling, propeller polish, anchor / chain inspection.
Regulatory detail & full definition
Standard drydocking cycle is 5-yearly aligned with the renewal special survey under IACS UR Z3 / Z7. One intermediate drydocking is permitted up to 2.5 years from the special survey, allowing many ship types to operate on a 5-yearly cycle. Some ship types and class notations allow extended in-water survey schemes that defer drydocking to 7.5 years subject to specific underwater inspection criteria. Cruise ships, tankers, and bulkers each have detailed schedules; the master and superintendent track due dates carefully because overrun without class approval invalidates certificates.
Authoritative source: IACS Unified Requirements ↗
Related
Source: IACS UR Z3 / Z7
High confidence
Editorial confidence: how we grade.