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 LL26 Rev2 CLN

UI LL26 Continuous hatchways as trunk (Regulation 36) - Rev.2 July 2008

UI LL27 Rev1 CLN

UI LL27 Less than standard hatch coamings on trunks of less than standard height (Regulation 36(4)) - Rev.1 July 2008

UI LL28 Rev1 CLN

UI LL28 Deduction for superstructures and trunks (Regulations 37 and 38(12)) - Rev.1 July 2008

UI LL29 Rev2 CLN

UI LL29 Sheer Credit for Superimposed Superstructures (Regulation 38(5), 38(7) and 38(12)) - Rev.2 July 2008

UI LL30 Rev1 CLN

UI LL30 Sheer allowance for excess height of superstructure (Regulations 38(7) and 38(12)) - Rev.1 July 2008

UI LL31 Rev1 CLN

UI LL31 Deduction for excess sheer (Regulation 38(15)) - Rev.1 July 2008

UI LL32 Deleted

UI LL32 Special requirements for vehicle ferries, ro-ro ships and other ships of similar type Withdrawn Oct 2007, re-categorised as UI SC220 (NEW Oct 2007)

UI LL33 Rev1 CLN

UI LL33 Timber freeboards for ships having reduced Type B freeboards assigned (Regulations 45(2) and 45(3)) - Rev.1 July 2008

UI LL34 Corr1 CLN

UI LL34 Freeboard for lighters and barges (Regulation 27(11) of 1966 ILLC) - Corr.1 July 2008

UI LL35 Corr1 CLN

UI LL35 Stowage of timber deck cargo on ships having timber freeboards assigned (Regulations 44 and 45) - Corr.1 July 2008

UI LL36 Rev2 CLN

UI LL36 Minimum wall thickness of pipes (Regulations 19, 20 and 22) - Rev.2 July 2008

UI LL37 Rev2 CLN

UI LL37 Superstructures with sloping end bulkheads (Regulations 34, 35 and 38(12)) - Rev.2 July 2008

UI LL38 Rev2 CLN

UI LL38 Bow Height (Regulation 39(2)) - Rev.2 July 2008

UI LL39 Rev1 CLN

UI LL39 Structure of a lower freeboard deck (Regulation 3(9)) - Rev.1 July 2008

UI LL40 Rev2 CLN

UI LL40 Security of hatch covers (Regulation 15(13)) - Rev.2 July 2008

UI LL41 Rev1 CLN

UI LL41 Trunks (Regulations 29, 36 and 38) - Rev.1 July 2008

UI LL42 Rev1 CLN

UI LL42 Access openings on barges (Regulation 27(11)) - Rev.1 July 2008

UI LL43 Rev1 CLN

UI LL43 Minimum bow height (Regulation 39) - Rev.1 July 2008

UI LL44 Rev1 CLN

UI LL44 Freeing ports (Regulation 24(3)) - Rev.1 July 2008

UI LL45 Rev2 CLN

UI LL45 Presentation of stability data (Regulation 10(2)) - Rev.2 Aug 2008

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