Marine fabrication is the cutting, welding, forming and finishing of metal components and structures for use in or near saltwater environments. It covers vessel repairs, on-board installations, jetties, dredging equipment and offshore platforms. The discipline is governed by classification society standards including Lloyd's Register, DNV and Bureau Veritas.

A corroded deck plate flagged at class survey. A dredger that needs a structural repair before her next contract. An offshore substation that needs a bespoke transition piece welded to EXC4. Three different jobs. One discipline behind all of them.

This guide explains what marine fabrication is, the four core processes involved, the materials and standards that govern it, and how to spot a fabricator capable of doing the work properly. If you procure fabrication services for ships, ports or offshore projects, you need this reference.

How Marine Fabrication Differs From Structural Fabrication

Both disciplines cut, weld and form metal. The difference is the operating environment and the rules that apply.

Marine work has to survive saltwater, vibration, fatigue loading and constant temperature swings. That changes the materials you can use, the coatings you must specify and the welding procedures you have to qualify. General structural fabrication has no such constraints.

The other difference is classification. A marine fabricator producing load-bearing work for a vessel or offshore asset must hold welder and procedure qualifications approved by a recognised class society. A structural steel shop building a warehouse frame does not.

The 4 Core Processes in Marine Fabrication

Marine fabrication breaks down into four core processes:

1. Cutting the raw plate, pipe or section to size.
2. Welding components together to a qualified procedure.
3. Forming plate and section into the required shape.
4. Finishing the assembly with surface prep, paint or coating.

Every job, from a small bracket to a full hull section, runs through some combination of these four stages. Each one is covered below.

Cutting

Cutting is the first stage of any marine fabrication job. The method depends on material thickness, tolerance and the geometry of the cut.

Plasma cutting handles mild and stainless steel plate up to around 50mm. Oxy-fuel cutting is used for thicker carbon steel sections. Laser and waterjet cutting deliver tighter tolerances for precision components. For pipework and smaller stainless work, mechanical sawing and CNC routing are common.

The cutting method affects the heat-affected zone and edge quality, which both feed into how the part welds. Cut quality matters before a single weld is struck.

Welding

Welding is the heart of marine fabrication. It is also the most heavily regulated stage of the process.

The main welding processes used in UK marine fabrication are MMA (stick), MIG/MAG, TIG and submerged arc welding. Each is suited to different materials, positions and joint types. TIG is the go-to for stainless and aluminium pipework. MIG/MAG handles the bulk of structural mild steel. Submerged arc covers long, heavy linear welds.

Every weld carried out for a classed asset must follow a qualified Welding Procedure Specification, and be performed by a welder qualified against that procedure. That is what a Lloyd's WPQR confirms.

Forming

Forming shapes plate and section into the curves and angles a marine structure needs.

Rolling produces shells, cones and curved hull plate. Press braking creates accurate folds for brackets, gussets and structural plate work. Hot forming is used on heavier sections where cold work would risk cracking. The skill is in matching the forming method to the material grade so the metallurgy is preserved.

Forming is where a good marine fabricator earns their fee on complex geometries. Anyone can cut a flat plate. Rolling a true cone to a tight tolerance is a different job.

Finishing

Finishing protects the finished fabrication from the marine environment. Skip it or rush it, and the asset corrodes years before it should.

Standard finishing involves grit blasting to a profile such as SA2.5, applying a marine-grade primer, then a topcoat system specified for the exposure zone. Splash zone coatings differ from atmospheric zone coatings, which differ again from submerged zone systems. The coating spec is dictated by the asset's classification and intended service life.

Welds are dressed back, edges are ground, and the surface is prepped to a documented standard before paint goes on. Trust this stage to the wrong contractor and the rest of the work is wasted.

Materials Used in Marine Fabrication

Material selection is a procurement decision, not just a technical one. The wrong choice costs you in either upfront price or in-service failure.

Mild steel is the workhorse. Most structural marine fabrication uses S275 or S355 grades, protected by a marine coating system. It is well understood, readily available and economical.

Stainless steel earns its place where coating failure is not an option. Grade 316 and duplex 2205 dominate in pipework, fittings and any wetted component that has to last decades without intervention.

Aluminium is chosen when weight matters more than cost. Naval craft, fast workboats and superstructures use marine grades like 5083 and 6082. It welds well but needs a qualified procedure and clean shop conditions.

Hardox is a wear-resistant steel used where abrasion will destroy mild steel in months. Think dredger components, chutes and bucket linings. It is harder to weld and form, and demands a fabricator who knows the metallurgy.

Marine Fabrication Standards and Classification Societies

This is the section that decides whether your tender process produces a credible shortlist or a list of risks. Get the certifications wrong on the spec and the rest does not matter.

BS EN 1090-2 and Execution Classes

BS EN 1090-2 is the European standard for the execution of steel structures. It defines four Execution Classes, EXC1 through EXC4, based on how serious the consequences of failure are.

• EXC1 covers simple structures with low consequences.
• EXC2 is most general structural steel.
• EXC3 is for buildings and structures with higher risk profiles.
• EXC4 is the highest class, required where failure would have severe consequences.

Load-bearing marine structures typically require EXC3 or EXC4. If a fabricator is not certified to the class your job demands, they cannot legally execute the work.

BS EN ISO 3834-2

ISO 3834-2 sets the "comprehensive quality requirements" for fusion welding of metallic materials. It is the welding-specific quality system that sits behind BS EN 1090 certification.

In plain terms, ISO 3834-2 is the standard that proves a fabricator has the procedures, records, equipment and qualified personnel to weld safety-critical work. It is the welding equivalent of asking to see someone's ISO 9001.

Lloyd's Register WPQR

A Lloyd's WPQR is a Welder and Procedure Qualification Record. It confirms that both the welding procedure and the individual welder have been tested and approved by Lloyd's Register for specified materials, positions and joint types.

WPQRs are material-specific. A fabricator approved for mild steel is not automatically approved for stainless. When you specify "Lloyd's approved welding," you need to specify the materials too.

DNV and Bureau Veritas

DNV and Bureau Veritas are the two other major classification societies you will encounter. DNV is dominant in Scandinavian and offshore energy markets. Bureau Veritas has strong coverage in French-influenced markets and a wide global presence.

For UK-based marine fabrication, Lloyd's is the default. For international projects or offshore work, you may need DNV or BV approval on top.

Where Marine Fabrication Happens

Marine fabrication is not a single location. It happens across three operational contexts, and a good fabricator covers all three.

Workshop Fabrication

Workshop fabrication happens in a controlled environment. It suits large structures, pre-assembly work and anything that needs precision tooling. Tolerances are tighter, quality is easier to control and output is faster.

Most new-build sections, jetty components and equipment skids are workshop-fabricated, then transported to site for final installation.

Quayside Fabrication

Quayside work is done at berth, alongside the vessel or structure. It is the bridge between workshop fabrication and on-board fitting.

This is where final adjustments, dimensional fit-up and large component installation happen. Cranage, hot work permits and port access controls all factor in.

On-Board Fabrication and Welding

On-board work is the hardest of the three. You are welding in confined spaces, around live vessel systems, often under time pressure.

Hot work permits, gas freeing of adjacent tanks, ventilation and competent supervision are all non-negotiable. A welder qualified for shop work is not automatically competent for on-board work. The risk profile is completely different.

Emergency Mobilisation

Vessel downtime is expensive. A workboat out of class costs the operator daily. An offshore asset offline costs more. When a fabrication job becomes an emergency, the question is not "can you do it" but "can you be at the berth tomorrow with the right ticket."

Multi-site UK fabricators can mobilise to most UK ports inside 24 hours. Single-shop operators cannot. This is a procurement reality that rarely makes it into competitor blogs.

Where Marine Fabrication Is Used

Marine fabrication serves four main sectors in the UK.

Vessels and Shipping

Commercial vessels, naval craft, workboats and dredgers all need fabrication through their service life. New-build hull sections, refit work, structural repairs, deck fittings and pipework all sit under marine fabrication.

Ports and Harbours

Jetties, fender systems, gangways, mooring structures and bollards are all marine-fabricated steel. Port operators procure this work for both new infrastructure and ongoing maintenance.

Offshore Energy

Offshore wind has been the growth sector for UK marine fabrication. Transition pieces, foundation components, secondary steelwork and topside structures are all in scope. Oil and gas continues to drive demand for platform repair and decommissioning work.

Naval Bases and Defence

MoD work covers naval vessel support, dock infrastructure and secure-site fabrication. Security clearance and supply chain compliance matter as much as technical capability here.

Dredging

Dredging contractors are heavy users of wear-resistant fabrication. Buckets, cutter heads, suction pipework and chutes wear out fast and need replacement on tight schedules.

How to Choose a Marine Fabrication Supplier in the UK

Use this checklist when shortlisting suppliers:

• BS EN 1090-2 EXC3 or EXC4 certification, matched to your project class.
• BS EN ISO 3834-2 for welding quality management.
• Lloyd's WPQR (or DNV / BV equivalent) for the specific materials in your scope.
• Geographic coverage across UK ports relevant to your operations.
• Demonstrable on-board capability, not just workshop work.
• Emergency response track record with named examples.
• Insurance and HSE record appropriate to marine work.

A supplier missing two or more of these is not a marine fabricator in the procurement sense. They are a general steel shop with marine work on the website.

Frequently Asked Questions

What is marine fabrication in simple terms?

Marine fabrication is the cutting, welding, forming and finishing of metal to make components and structures for ships, ports and offshore assets. It is governed by class society standards like Lloyd's Register, and uses materials chosen to survive saltwater service.

What is the difference between marine fabrication and steel fabrication?

Steel fabrication is a general discipline. Marine fabrication is steel fabrication carried out to class society approval, in marine-grade materials, with qualified welding procedures and coatings designed for saltwater service. The difference is environment and regulation.

What certifications should a UK marine fabricator have?

A credible UK marine fabricator should hold BS EN 1090-2 at EXC3 or EXC4, BS EN ISO 3834-2 for welding quality, and Lloyd's WPQR (or DNV / BV equivalent) for welder and procedure qualifications covering each material in scope.

What materials are used in marine fabrication?

The four main materials are mild steel grades like S275 and S355 for structural work, stainless grades like 316 and duplex 2205 for corrosion-critical applications, marine aluminium grades like 5083 and 6082 for weight-sensitive builds, and Hardox wear plate for abrasion-heavy components.

Does marine fabrication happen on board vessels?

Yes. Marine fabrication is carried out in workshops for major assemblies, at quayside for fitting and large installation, and on board vessels for repairs, modifications and emergency response. Multi-site fabricators mobilise teams to UK ports at short notice to minimise vessel downtime.

Choosing the Right Marine Fabrication Partner

Marine fabrication is a regulated discipline defined by environment, standards and the operational reality of working on vessels. The fabricator you choose is not just supplying metalwork. They are underwriting the reliability of your asset.

The right partner holds the certifications your project demands, covers the UK ports you operate from, and proves they can mobilise when downtime is on the line.

EAP Ltd delivers full-service marine fabrication from nine UK locations and Romania, with BS EN 1090-2 EXC4 certification, Lloyd's WPQR-approved welding for mild and stainless steel, and a 20-year track record across vessels, ports and offshore projects. We also offer steel fabrication, mechanical engineering and design services as part of the same package.

Contact our marine fabrication team to discuss your project, or tell us which UK port you need cover at and when.