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 LL46 Rev3 CLN

UI LL46 Protection of openings in raised quarterdecks (Regulation 18(2) and Interpretation LL8) - Rev.3 July 2008

UI LL47 Rev3 CLN

UI LL47 Guard Rails - Rev.3 July 2008

UI LL48 Rev2 CLN

UI LL48 Moulded Depth (Regulation 3(5)(c) and 3(9) and Freeboard Calculation (Regulation 40(1)) - Rev.2 July 2008

UI LL49 Rev1 CLN

UI LL49 Air pipe closing devices (Regulation 20) - Rev.1 July 2008 CLN

UI LL50 Rev5 CLN

UI LL50 Protection of Crew (Load Line Convention Regulation 25(4), 26(2) and 27(7) and SOLAS II-1/3-3) - Rev. 5 July 2008 Clean

UI LL51 Rev2 CLN

UI LL51 Freeboards greater than minimum (Regulation 2(5)) - Rev.2 July 2008 CLN

UI LL52 Rev1 CLN

UI LL52 Weathertight closing appliances for ventilators (Regulation 19(4)) - Rev.1 July 2008 CLN

UI LL53 Rev1 CLN

UI LL53 Treatment of moonpools - Rev.1 July 2008 CLN

UI LL54 Rev1 CLN

UI LL54 Effective length of superstructures (Regulation 35(3)) - Rev.1 July 2008 CLN

UI LL55 Rev1 CLN

UI LL55 Least Moulded Depth for a Ship with a Rake of Keel (Regulation 3(1)) - Rev.1 July 2008 Clean

UI LL56 Rev1 CLN

UI LL56 Block Coefficient of a Pontoon (Regulation 3(7)) - Rev.1 July 2008 Clean

UI LL57 Rev1 CLN

UI LL57 Block Coefficient of a Multi-hull Craft (Regulation 3(7)) - Rev.1 July 2008 Clean

UI LL58 Rev1 CLN

UI LL58 Machinery space and emergency generator room ventilator coaming heights (Regulations 17(2), 19(3) and 19(4)) - Rev.1 July 2008 Clean

UI LL59 Rev1 CLN

UI LL59 Cargo manifold gutter bars - freeing arrangements and intact stability- Rev.1 Dec 2007 Clean

UI LL60 Rev1 CLN

UI LL60 Freeing ports in way of wells in combination with open superstructures (Regulation 24(1) and 24(4)) - Rev.1 July 2008 Clean 

UI LL61 Rev1 CLN

UI LL61 Method of correction for the effect of free surface of liquids in tanks (Regulation 10(2), UR L3 and UI LL45) - Rev.1 July 2008 Clean

UI LL62 Rev1 Corr1 CLN

UI LL62 Side Scuttles, Windows and Skylights (Regulation 23) - Rev.1 Corr.1 - August 2010

UI LL63 Rev2 CLN

UI LL63 Treatment of steps and recesses in transverse subdivision bulkheads: IMO Res. A.320 (IX), paragraphs 12(d) and 12(e), and Regulation 27(12)(d) and (e), Revised 1988 ICLL (MSC.143(77)) - Rev.2 July 2008 Clean

UI LL64 Rev5 CLN

UI LL64 Non-weathertight hatch covers above superstructure deck (Load Line Convention 1966 Regulations 2(5) and 14(2)) - Rev.5 July 2008 Clean

UI LL65 Rev2 CLN

UI LL65 Ships with assigned or reassigned reduced freeboards and intended to carry deck cargo - Rev.2 July 2008 Clean

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