Dry Dock Planning: Specification, Survey Windows & Cost Control

Survey Windows: When the Ship Must Dock

Docking is driven by the statutory and class survey regime, not by preference. In outline, under the SOLAS survey framework the outside of the ship's bottom must be inspected at least twice in any five-year period, and the interval between two such inspections must not exceed 36 months.

That maps onto the classification cycle most superintendents work to:

The practical planning point: these windows are known years ahead. A fleet docking programme should be a rolling multi-year plan with budget attached, not an annual surprise — and the survey calendar in your maintenance system is where it should live.

UWILD and In-Water Survey

UWILD — Underwater Inspection In Lieu of Drydocking — allows an in-water survey by approved divers or ROV to substitute for one of the required bottom inspections. Where accepted it removes an entire off-hire docking from the cycle, which is a substantial commercial saving.

Acceptance is conditional, and the conditions are where plans fail:

• Ship type and age — concessions commonly narrow as tonnage ages.
• Class and flag approval — arranged in advance, not assumed.
• Approved diving contractor with the right equipment and reporting capability.
• Water clarity and location — visibility must permit meaningful inspection; suitable sheltered locations are limited.
• Hull condition and cleanliness — a fouled hull cannot be surveyed; cleaning may be needed first.
• Specified items must be inspectable — rudder, propeller, sea chests, and the ability to record findings for the surveyor.

Plan UWILD as a project of its own: approvals, location, contractor and hull condition all need lead time.

A Realistic Planning Timeline

Building a Specification That Controls Cost

The specification is the single most powerful cost-control instrument you have, because it is written while yards are still competing. A weak specification transfers pricing power to the yard the day the ship arrives.

Where a good specification comes from:

1. Statutory and class items — everything due at this survey, from the class survey list.
2. Deferred and postponed jobs — from the PMS. This is why maintenance record quality directly determines docking cost: jobs quietly postponed for two years reappear here, unpriced.
3. Open defects — the defect register, prioritised.
4. Condition data — thickness measurements, coating condition reports, previous docking findings.
5. Owner's improvement work — efficiency, habitability, regulatory upgrades.
6. Standard docking scope — hull treatment, anodes, sea valves, anchor chain ranging, tailshaft, tank inspections.

Yard Selection and Tendering

• Tender the same document to every yard, or the quotes are not comparable.
• Normalise the comparison — dock rate, day rate, unit rates, cranage, staging, services, gas-freeing, waste disposal and berth charges all differ in what they include.
• Cost the position, not just the price. A cheaper yard three days' steaming away can cost more once off-hire, bunkers and the deviation are counted.
• Check real capability — dock dimensions, crane capacity, coating facilities, workshop capacity, and current order book (a busy yard delays).
• Confirm attendance — class surveyor, flag, makers' specialists and owner's superintendents all need to be there at the right time.
• Agree the variation process in writing before signing, including who may authorise what value.

Growth Work — Where Budgets Die

Growth work is everything discovered after the ship is in dock: extra steel once the coating comes off, corrosion behind linings, defects found when machinery is opened. It is the dominant cause of docking overruns, for a structural reason — at that moment the ship is captive. It cannot leave, and the yard faces no competitive pressure.

You cannot eliminate growth work. You can price it in advance:

• Agree unit rates upfront for the probable growth items — steel renewal per tonne, staging, blasting per m², pipe renewal.
• Reduce the unknown before arrival — thickness measurements, tank inspections and coating surveys done early convert surprises into specified scope.
• Hold a contingency — a realistic percentage of contract value, sized by ship age and condition, approved in advance so a decision does not wait on a budget conversation.
• Written variation orders only. No verbal instructions, ever. Every variation priced and signed before work starts.
• Review cost daily against the approved envelope, not weekly.

The Critical Path in Dock

Duration is usually governed by a small number of long-pole activities. Identify them and protect them:

Two habits pay for themselves: order owner-supplied items early (late spares are a self-inflicted delay you also pay yard standby for), and hold a short daily progress meeting with the yard where slippage is identified while it is still one day rather than five.

Hull Coating as a Fuel Decision

The coating specification is usually treated as a maintenance line item. It is better understood as a fuel-efficiency investment, because hull and propeller condition are among the strongest operational influences on consumption — and therefore on carbon intensity.

• Surface preparation matters more than the product. A premium coating over poor preparation underperforms a modest coating applied properly.
• Match the coating to the trade — idle time, water temperature and speed profile all change what performs.
• Do not skip the propeller. Polishing is inexpensive relative to its effect on consumption.
• Model the payback in fuel, not just in coating cost — over a five-year cycle a fuel-efficiency difference of even a few percent typically dwarfs the price gap between specifications.
• It feeds your rating. Hull condition is a lever on CII performance, so the docking decision is now partly a compliance decision.

Frequently Asked Questions

How often must a ship be dry-docked?

Generally the ship's bottom must be inspected at least twice in any five-year period, with no more than 36 months between inspections — aligned to the class survey cycle. Requirements vary by ship type, age and flag.

What is UWILD?

Underwater Inspection In Lieu of Drydocking — an approved in-water survey substituting for a bottom inspection, subject to class and flag approval and conditions on age, hull condition, visibility and contractor.

How do you control dry-dock costs?

Through a precise specification, like-for-like tendering, pre-agreed unit rates for growth work, pre-arrival surveys that reduce unknowns, and strict written change control.

What is growth work?

Work discovered after the ship is in dock and the specification was priced — the main cause of overruns, because the ship is captive and competitive pressure is gone.

How does docking affect CII?

Hull and propeller condition strongly influence fuel consumption, so coating and polishing decisions in dock directly affect subsequent carbon intensity performance.

Scope & Sources

This guide is a general planning overview for superintendents, not a survey or classification reference. Survey intervals, concessions and UWILD acceptance vary by ship type, age, flag Administration and classification society, and are subject to amendment. Always confirm the actual requirements and windows for each specific vessel with your class society and flag Administration before planning or deferring a docking. Nothing here constitutes classification, legal or engineering advice.