Introduction To Ship Load Lines

If we try to define Load Line in the simplest fashion, it will be as follows:

“Load line is a special marking positioned amidships which depicts the draft of the vessel and the maximum permitted limit in distinct types of waters to which the ship can be loaded.”

As a result of the numerous maritime accidents that have happened at sea due to the overloading of vessels, the significance of having a standard maximum limit for ships was identified long before. However, it took many years from then to have an International agreement for the universal application of Load lines.

It was in 1930, when the first International Load Line Convention took place, after which, it was periodically amended until the latest one that happened in 2003.

Ship Load Line
Image Credits: Marine Insight

In order to make a complete comprehension of Load Lines, we must address the following questions:-

  1. What is the purpose of Load Line?
  2. Why is it necessary for ships to have Load Lines?
  3. What exactly is a Load Line?
  4. What is the marking on a Load line?
  5. What are the different types of Load Lines?

Purpose and Necessity of Load Lines

The fundamental purpose of a Load Line is to allow a maximum legal limit upto which a ship can be loaded by cargo. By prescribing such limits, the risk of having the vessel sailing with inadequate freeboard and buoyancy can be limited. A vessel should be having sufficient freeboard at all times, any exceptions made will result in insufficient stability and excessive stress on the ship’s hull. This is where load-lines play an important role, as it makes the task of detecting whether the vessel is overloaded and its freeboard tremendously easy and effortless.

However, since the buoyancy and immersion of the vessel largely depend on the type of water and its density, it is not practical to define a standard freeboard limit for the ship at all times. For this reason, the load line convention has put regulations that divide the world into different geographical zones each having a different prescribed load line.

For example, A vessel sailing in Winter on North Atlantic Ocean will have a greater freeboard than on a voyage in Tropical Zones and Freshwaters.

Understanding Load Line Mark

As we have already defined above, the Load Line is a special marking positioned amidships. All vessels of 24 meters and more are required to have this Load line marking at the centre position of the length of the summer load waterline.

There are two types of Load line markings:-

  1. Standard Load Line marking – This is applicable to all types of vessels.
  2. Timber Load Line Markings – This is applicable to vessels carrying timber cargo.

These marks shall be punched on the surface of the hull, making it visible even if the ship side paint fades out. The marks shall again be painted with white or yellow colour on a dark background/black on a light background. The complete Load line markings consist of 3 vital parts.

  1. Deck Line – It is a horizontal line measuring 300mm by 25mm. It passes through the upper surface of the freeboard.
  2. Load Line Disc – It is a 300mm diameter and 25mm thick round shaped disc. It is intersected by a horizontal line. The upper edge of the horizontal line marks the ‘Summer saltwater line’ also known as ‘Plimsol Line’.
  3. Load Lines – Load lines are horizontal lines extending forward and aft from a vertical line placed at a distance of 540mm from the centre of the disc. They measure 230mm by 23mm. The upper surfaces of the load lines indicate the maximum depths to which the ships may be submerged in different seasons and circumstances.

S – Summer:- It is the basic freeboard line at the same level as the Plimsoll Line. Other load lines are marked based on this Summer freeboard line.

T – Tropical:- It is 1/48th of the summer draft marked above the Summer load line.

W – Winter:- It is 1/48th of the summer draft marked below the Summer load line.

WNA – Winter North Atlantic:- It is marked 50mm below the Winter load line. It applies to voyages in North Atlantic ( above 36 degrees of latitude) during the winter months.

F – Fresh Water:- It is the summer freshwater load line. The distance between S and F is the Fresh Water Allowance (FWA).

TF – Tropical Fresh Water:- It is the freshwater load line in Tropical. It is marked above the T at an amount equal to FWA.

Watch the video explaining Load line/ Plimsoll line on the ship

Timber Load Line Markings

Ships engaged in the timber deck cargo trade are required to have a special set of Load lines known as the Timber Load Lines. Such vessels shall comply with the Code of Safe Practices for Ships Carrying Timber Deck Cargo in construction and other requirements obtaining greater reserve buoyancy and lesser summer freeboard.

timber load line
Image Credits: Deck Officer Nachiketh Bhattathiri


Timber cargo vessels will have a second set of Load Lines marked similar to the standard load-lines positioned 540mm above the centre loadline disc.

The letter marking of the timber loadline is different and are prefixed by ‘L’ meaning ‘Lumber’.

LS – Lumber Summer:- Its upper edge marks the summer saltwater timber loadline. It is situated at a specified level above the Plimsol line.

LW – Lumber Winter:- It is 1/36th of the lumber summer draft below LS.

LT – Lumber Tropical:- It is 1/48th of the lumber summer draft above LS.

LWNA – Lumber Winter North Atlantic:- It is at the same level as WNA.

LF – Lumber Freshwater:- It is situated above the LS by an amount equal FWA.

LTF – Lumber Tropical Fresh Water:- It is positioned above LT by an amount equal to FWA.

International Loadline Certification

Every ship that has been surveyed and marked in accordance with the present Load line convention are issued by the authorized administration, an International Load Line Certificate. The certificate will have a validity of not more than 5 years and will contain all vital information that includes the assigned freeboard and freshwater allowance.

It is to be noted that, after completion of a load line survey and issuance of the certificate; no changes shall be made to the superstructure, markings, equipment or arrangements that have been covered under the survey. If such changes need to be made, the authorized authority conducting the survey shall be contacted.

Over to you..

If you have more points to mention on ship load-lines please go ahead, We would like to see them as comments!

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 


  1. @ suamil Thanki:

    The Circle in the loadline has two significance:

    1. The circle with the line through it indicates whether or not the cargo is loaded evenly

    2. In earlier days, the line in the circle was taken as a reference for maximum draught of the ship, which is now same as summer load line of the ship.

  2. @ Saumil :

    The circle is the load line disc and the letters on either of its side is simply the abbreviation of the classification society which has done the survey and issued the certificate. In the above image ‘AB’ is the abbreviation of ABS Classification Society.

    Please read above the Load Line subtitle.

  3. Just to correct you,

    1) Stress & stability problems do not result from overloading. You might be loaded above the required load line marks but still have good GM and stresses well within limits and you might be half way from load line marks and still have unacceptable stresses. The purpose of load lines is to ensure vessel has sufficient reserve buoyancy (and not stress and stability).

    2) The load lines zones are not divided on the basis of type of water & density (as claimed in this post) but on the basis of weather conditions in that geographical area that warrants the ships to be loaded lower (which is Winter Loadline) or above (which is Tropical loadline) summer loadline. Fresh water marks are given to give the indication of loading in fresh water so that when the vessel arrives at sea, she is at her allowed loadline.

    Considering the rank of the author, Well Done.

  4. it’s answers my question..i help load/unload ships for seaboard/jacintiport, Houston…always wondered what the marks were for…

  5. If sea water density more or less remains same, then why ships draft reduces in winter north how seasons causes draft changesss…

  6. Classification Societies…

    ABS – American Bureau of Shipping (USA) *Largest
    BV – Bureau Veritas (France)
    CCS – China Classification Society (China)
    DNV – Det Norske Veritas (Norway)
    GL – Germanischer Lloyd (Germany)
    IRS – Indian Register of Shipping (India)
    KRS – Korean Register of Shipping (Korea)
    LR – Lloyd’s Register of Shipping (UK) *Oldest
    NK – Nippon Kaiji Kyokai (Japan)
    RINA – Registro Italiano Navale (Italy)
    RS – Russian Maritime Register (Russia)
    CRS – Croation Register of Shipping (Croatia)

  7. .In determining load line zones , both weather and density factors are included or on weather ?

  8. .In determining load line zones , both weather and density factors are included or only weather ?

  9. timber loadline is assigned for ship carrying timber cargo on deck and standard loadline is for any type of ship.

  10. The first illustrating diagram hand an error in the thickness value it should be 25 mm not 23 mm. Plimsol was a real good blissed person he was a cause to save other seafarers life from sinking at heavy weather sea.

  11. In addition, The WNA applies only to vessels less than or equal to 100 meters in length. Thank you.

  12. Any one can tell me the meaning of the following abreviation SEP in maritime methodology
    Thanks a lot

  13. please clear my doubt. if i load from winter seasonal zone what loadline shld. be follow the winter load line. or the summer load line ? is there any specific density for TF, F, T, S, W, WNA? What thats mean of 1/48 from summer to tropical / and winter?

  14. Hi jack says,
    If you load cargo in winter seasonal zone, you have to load just to winter load line. This means your appropriate load line must be always above the water level in all seasonal zones throughout your voyage, thanks

  15. Hi,
    please clear my doubt,
    If vsl load in the tropical seasonal zone and discharge in the winter zone which load line need to use in the loading port.

  16. A LOAD LINE CONDITIONS OF ASSIGNMENT SURVEY will be performed by the surveyor with following important criteria:
    Freeboard, Stability, Ship type, deck openings, watertightness arrangement etc.

  17. can you explain how the draft marks 2, 4, 6….are read??? say suppose the waterline is just touching 2 then should we consider it as 2m or the 2 should be completely immersed to take as 2m

  18. please clear my doubt,
    If vsl load in the tropical seasonal zone and discharge in the summer zone which load line need to use in the loading port.

  19. Hay Point is in the Tropical Load Line Zone. The area outside the Great Barrier Reef is in the South Pacific Seasonal Tropical Zone.
    Tropical: From 1 April to 30 November;
    Summer: From 1 December to 31 March.

  20. How does a ship superintendent relate their job scope to load lines regulations during site duties?

  21. @Hai: Multiple load lines are used when, for a period of time, a FG cargo ship has a need to operate temporarily with a greater freeboard than the minimum freeboard stipulated in accordance with the International Convention on Load Lines. IN Many ports, the port dues are calculated as per the deadweight of the ship and some ports have a restriction on maximum deadweight of the ship. with multiple ladling, the owners can reduce or increase the deadweight according to their requirement.

  22. please help me this ques come on mca writen exam i couldn’t fiend the ans
    **explain the importance of EACH of the following with reference to the purpose of the load line survey.
    1.bilge system
    2.ballast system

  23. Sir pls clear my doubt on these question when we can add 0.025 either water lineabove or below summer draft and wats the difference betwwen intial and present draft

  24. Can I load the vessel and exceed summer draft when I am in summer Zone. In example, my mean draft , amidship is 16,5, summer draft16,9, aft 17,1 fwd 16,1. In this scenario i have exceeded summer draft the stern, but at the plimsol mark, midhsip is not exceeded. Correct If I am wrong, but to fulfill the requirements the mean draft must not exceed the summer draft ?

  25.  Which load line you use in the month of July ( you are proceeding from IRAN to WEST coast of INDIA)

  26. Why vessel less than 100 m are assigned to wna load line wile trading in winter in atlntic area

  27. @Radek As per the LL convention, the ship cannot be submerged at the appropriate load line, in still water, at a density of 1.025kg/l. It is legal to load the ship to the load line and have stern trim.

  28. @anscar Whatever zone the ship is sailing in is the loadline that the ship cannot exceed. You can exceed the summer draft in a tropical zone, consume fresh water and fuel oil to reduce the draft before you get to the summer zone.

  29. Hello, may I ask permission to use an image from this article. It is the image of the load line near the top of this page with credit Marine Insight. I would like to use this image in a children’s educational book called Extreme Science: Forces in a section explaining how ships float. It would be used very small, thumbnail-sized on an inside page.

    Many thanks

  30. @Abdel Naseer: In the case of a ship being assigned a freeboard greater than minimum so that the load line mark is marked at a position corresponding to or lower than the lowest seasonal load, and line assigned at a minimum freeboard is in accordance with the calculation procedure, only the Fresh Water Load Line needs to be marked. Such load lines are termed “All Seasons Load Lines” and are illustrated in the photo.

  31. @Spencer hello. i have got two question about this all season load line
    Q1,If only Fresh Water Load Line need be marked, ships navigate in Tropical Fresh Water Area will bear a loss of freeboard by d/48. Are there any details can support to explain the reason of this amendment.
    Q2:Does the “lowest seasonal load line” includes the Winter Load Line?

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