Unified Interpretations


Unified Interpretations are adopted resolutions on matters arising from implementing the requirements of IMO Conventions or Recommendations. Such adopted resolutions can involve uniform interpretations of Convention Regulations or IMO Resolutions on those matters which in the Convention are left to the satisfaction of the Administration or vaguely worded.

Interpretations are circulated to Administrations concerned or are sent to IMO for information, as appropriate.


  1. IACS, as an international Non-Governmental Organization having observer status at IMO, works in co-operation with IMO in order to endeavour that regulations developed at IMO are clear, unambiguous and can easily be applied without the need of interpretations.
  2. However, interpretations may still be needed in cases where IMO regulations contain only functional requirements, allow alternative solutions to prescriptive requirements, are left to the satisfaction of Administrations or are generally or vaguely worded.
  3. The following Unified Interpretations (UIs) have been developed by IACS to assist the unified implementation of IMO regulations falling in the above-mentioned cases. It should be noted that the development of IACS Unified Interpretations (UIs) is not aiming at introducing additional requirements but at achieving uniform application of IMO regulations.
  4. IACS UIs are to be applied by IACS Societies to ships whose flag Administrations have not issued definite instructions on the interpretation of the IMO regulations concerned, in the course of statutory certification on behalf of those flag Administrations.

The technical backgrounds (development histories) of Unified Interpretations since 2004 can be found by following this link.

A list of the IACS working groups responsible for each Unified Interpretation may be found here.


UI LL6 Hatchways closed by weather tight covers of steel or other equivalent material fitted with gaskets and clamping devices (Regulations 16 and 27(7)(c)) - Rev.3 July 2008 Clean


UI LL7 Machinery space openings (Regulations 17(1), 26(1), 27(8) and 27(9)) - Rev.2 July 2008 Clean


UI LL8 Miscellaneous openings in freeboard and superstructure decks (Regulation 18(2) & 18(3)) - Rev.1 July 2008

UI LL9 Deleted


UI LL10 Rev1 CLN

UI LL10 Air pipes (Regulation 20) - Rev.1 July 2008

UI LL11 Rev3 CLN

UI LL11 Scuppers, inlets and discharges (Regulation 22(1)) - Rev.3 July 2008

UI LL12 Deleted

UI LL12 Deleted - July 2008

UI LL13 Rev1 CLN

UI LL13 Freeing ports (Regulation 24(1) and 24(5)) - Rev.1 July 2008

UI LL14 Rev1 Corr1 CLN

UI LL14 Protection of the crew (Regulation 25(2)) - Rev.1 Corr.1 Oct 2015

UI LL15 Rev3 CLN

UI LL15 Length of superstructure (Regulation 34(1) and 34(2))- Rev.3 July 2008

UI LL16 Rev1 CLN

UI LL16 Sheer (Regulation 38) - Rev.1 July 2008

UI LL17 Rev1 CLN

UI LL17 Minimum bow height (Regulation 39(1) and 39(2)) - Rev.1 July 2008

UI LL18 Rev1 CLN

UI LL18 Freeboard tables (Regulation 28) - Rev.1 July 2008

UI LL19 Rev1 CLN

UI LL19 Form of certificates (Article 18) - Rev.1 July 2008

UI LL20 Rev1 CLN

UI LL20 Hatch beams and cover stiffeners of variable cross section (Regulations 15(4), 15(5), 15(6), 15(7) and 16) - Rev.1 July 2008

UI LL21 Rev1 CLN

UI LL21 Cargo ports or similar openings below the uppermost load line (Regulation 21(2)) - Rev.1 July 2008

UI LL22 Rev1 CLN

UI LL22 Position of the inboard end of discharges when timber freeboard is assigned (Regulation 22(1)) - Rev.1 July 2008

UI LL23 Rev1 CLN

UI LL23 Freeing arrangement (Regulations 26(5), 27(7) and 36(1)(e)) - Rev.1 July 2008

UI LL24 Rev1 CLN

UI LL24 Negative depth correction (Regulation 31(3)) - Rev.1 July 2008

UI LL25 Rev1 CLN

UI LL25 Effective length of raised quarterdeck (Regulation 35(4)) - Rev.1 July 2008

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