What is the extent of thickness measurement on a general dry cargo ship?
Two things about this ship type catch people who come to it from bulk carriers. A transverse section here starts life as deck plating, not a cut through the girder. And every section, from the first, has to sit inside the amidships half of the ship — a condition the bulk carrier rules never impose on more than one.
The short answer
- First survey: suspect areas. The column beneath that line is empty.
- Second: one transverse section — deck plating only — over a cargo space, inside the amidships 0.5 L.
- Third: two sections in two different cargo spaces, still amidships, plus the deck outside the hatch line.
- Fourth and after: at least three sections, the deck outside the hatch line, and every bottom plate with the lower turn of bilge.
- Over fifteen, the intermediate survey is the special survey minus one named item.
Two IACS documents, overlapping ships
Before anything else, know which requirement you are reading. Two IACS documents cover ships in this family. One is the general hull survey requirement, and it is worth being exact about its reach: its own application clause says it applies to all self-propelled vessels — not, as is widely assumed, only to ships outside the enhanced survey programme. A further clause then sends tankers, bulk carriers, chemical tankers, dry cargo ships and gas carriers to the Z10 series and to its own siblings for the requirements that come in addition. The second document is written specifically for general dry cargo ships. They agree on the ladder and differ on what sits beside it. UR Z7 §1.1.1 · §1.1.3
The general requirement adds items the dry-cargo one does not. At the third survey it brings in all cargo hold hatch covers and coamings, plating and stiffeners, and the internals of the fore and after peak ballast tanks. The dry-cargo requirement's column at the same survey carries neither. UR Z7 · UR Z7.1
And they part company entirely at the intermediate survey. The general requirement publishes no thickness measurement there at all — its intermediate section sets internal examination of ballast tanks and, for some ships, of cargo spaces, and stops. The dry-cargo requirement does set one, and above fifteen years it is the heaviest line in the whole regime. That difference is worth settling before a survey is quoted, not after.
The ladder
| Survey | Systematic extent |
|---|---|
| No.1 | Suspect areas, and nothing beneath that line — no section, no deck plate, no strake. |
| No.2 | One transverse section, deck plating only, over a cargo space, inside the amidships 0.5 L. |
| No.3 | Two sections, in two different cargo spaces, inside the amidships 0.5 L; and each deck plate outside the hatch-opening line within the cargo length. |
| No.4 and after | At least three sections, inside the amidships 0.5 L; the deck outside the hatch line; every bottom plate with the lower turn of bilge. |
DNV again leaves the first column entirely blank and prints no suspect-areas line in that table at all — a drafting choice, not a lower requirement, and the same one it makes on tankers and bulk carriers. DNV Table 10
A transverse section here is deck plating
The requirement says so in the column itself: at the second survey, one transverse section, deck plating only. Not a cut from keel to sheerstrake — the deck across the beam, over a cargo space.
That is the same distinction the tanker requirements draw at their first survey, and it has the same consequence for a quotation: the word section in this table does not carry the price a bulk carrier surveyor attaches to it. A programme built by analogy from a bulk carrier will over-scope the ten-year survey substantially. UR Z7.1 Table II
ABS adds a clarification the others leave implicit, and it is a useful one: the section is taken in way of a cargo space hatch opening — meaning the plating outside that opening. A section cut across a hatch is mostly coaming and air. ABS SPS 2
Every section sits amidships — and that is unusual
Read across the chapter and the placement rules line up like this. On a bulk carrier, one of the sections has to be in the amidship area and the rest are free. On a tanker, at least one inside 0.5 L amidships, with ABS confining all three. On a general dry cargo ship, every section — the first, the pair, the trio — sits inside the amidships 0.5 L, and that is the baseline requirement, not a class addition.
So the ship type with the smallest scheduled extent has the tightest placement rule in the chapter. It makes sense once you see what the sections are for: with only deck plating taken, and only three of them at twenty years, the sample is small enough that where it is cut decides whether it means anything.
Two further conditions ride with it from the third survey: the two sections go in two different cargo spaces, and the deck outside the hatch line comes in as a separate item. PRS reproduces both conditions in the same terms, which is worth knowing because its publication is the one written as guidance. PRS Pub 62/P
The heaviest line in the regime is in the intermediate survey
This is the one to carry away from the page, and it is invisible if a survey is planned from the special survey tables alone.
Above fifteen years the intermediate survey takes the whole special survey extent, and exactly one item is taken out: each bottom plate including the lower turn of bilge. Everything else in the fourth column comes across — three sections, the deck outside the hatch line, the close-up members. Tank testing, the automatic air pipe head survey and the internal examination of fuel oil tanks also drop out; the measurement extent does not. UR Z7.1 §4.2.4
Below that age the intermediate survey is light: between five and ten years nothing is scheduled beyond the suspect areas carried forward; between ten and fifteen, readings where the surveyor calls for them or where corrosion is extensive.
ABS builds the same requirement with its own exclusion: the previous special periodical survey's measurement requirement, with one named item not required. Different item, same construction — the intermediate survey is defined by subtraction from the special survey, and the subtraction is always short. ABS 7-3-2/5.15.4
Two scheduling provisions go with it, both useful on a job sheet. The survey may be spread — begun at the second annual and carried through the following year to finish at the third. And an in-water survey may be accepted in place of the dry-dock survey, on the terms of the separate IACS requirement that governs bottom surveys. UR Z7.1 §4.2.4.2 · §4.2.4.3
The annual survey, and the item that runs at every one of them
Nothing is scheduled for measurement at an annual survey — the same position as every other ship type in the chapter. Gauging arrives when the surveyor calls for it, where corrosion is visibly extensive, or through the suspect areas carried forward.
But one close-up item runs at every annual survey, at any age: the hatch cover plating, and the coaming plating with its stiffeners. There is no age qualifier on it anywhere. On a ship whose hatch covers are its weather boundary that is the right place to spend the attention, and it is the single most predictable annual gauging item on this ship type. UR Z7.1 §3.2.3
The rest of the annual ladder is by age. Between ten and fifteen years, an overall survey of one forward and one after cargo hold with their tween deck spaces. Over fifteen, that widens to all holds and tween decks, all the piping and penetrations in them including overboard piping — and the shell frame examination appears, which exists at annual surveys only above fifteen years. Where the hold coating is found GOOD its extent may be specially considered. UR Z7.1 §3.2.5
Ballast tanks reach the annual survey the same way they do everywhere: only where an earlier survey put them on a yearly cycle, and the condition for that is written out — a hard coating found POOR and not renewed, a soft or semi-hard coating, or no hard coating from new. The double bottom is carved out of it by the same change of verb this chapter has met before.
Escalation on a ship outside enhanced survey
The duty is the same as everywhere: once readings show substantial corrosion the extent is increased until the affected area is bounded, and the work is completed before the survey is credited.
The pattern is guidance. The table beside the clause is two lines — plating, the suspect area and the plates next to it on a five-point pattern over a square metre; stiffeners, the suspect area, three readings across the web and three across the flange — and the requirement offers it as something that may be used as guidance. There is no row for a girder, a floor, a bracket or a web frame.
One asymmetry to carry: the special survey clause states the escalation without a completion deadline, while the annual and intermediate clauses require the work before crediting. The deadline is real; it is simply not written in every clause that needs it. And PRS, whose publication for this ship type is the one that calls its own table guidance, attaches the hard obligation three times over — at the annual survey, at the intermediate, and at class renewal. UR Z7.1 §2.4.2 · PRS 62/P
Which closes the chapter where it opened: the obligation to widen is flat everywhere, and only the method softens.
Sources
- UR Z7.1 Rev.15IACS — General dry cargo ships, hull surveysofficial text ↗
- UR Z7 Rev.29IACS — Hull classification surveys, ships other than ESPofficial text ↗
- ABS Part 7ABS — Rules for Survey After Construction, Jul 2026official text ↗
- DNV Pt.7 Ch.1 Sec.4DNV — Rules for Classification: Ships, survey requirements, Jul 2022official text ↗
- PRS Publication 62/PPolish Register of Shipping — Hull surveys of general dry cargo ships, 2025official text ↗
Class-society and IMO documents are indexed and linked, never re-hosted. Where a class rule is stricter than the IACS baseline, the class rule governs.