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Builders Plate Requirements - What You Need to Know

In Australia, the person who completes a boat and supplies it for use becomes the “builder” in the eyes of the law. That responsibility includes obtaining a HIN, fitting a compliant Australian Builders Plate and ensuring the vessel meets the applicable safety standards. This page provides a high-level overview of those obligations, with links to authoritative references for further reading.

What Is an australian Builders Plate?

An Australian Builders Plate is a permanent plate fixed to the vessel that provides essential safety and compliance information, including:Maximum engine power.Maximum load and passenger capacity.Buoyancy or flotation statement.Builder details and year of manufacture. The boats unique HIN (Hull Identification Number)For kit boats and DIY builds, the builder is the individual or business completing the boat, not the kit supplier. It is common to refer to AS1799.1:2021 - General requirements for power boats or ABYS standards

AS1799.1:2021 - General Requirements for Power Boats

AS 1799 is the primary Australian Standard governing the safety of recreational boats. In 2021 the 2009 edition was superceded by a comprehensive update. The relevant sections to the Australian Builders Plate requirements are:Buoyancy and flotation principles.Load capacity. Power limits. Outboard Motor wight limits.Stability - inshore and offshore waters

Your Obligations as a Builder

If you complete a boat for your own use, or supply it to another party (including resale), you are responsible for ensuring that:The information on the Builder Plate is accurate and defensible.Load and power limits are calculated correctly.Buoyancy and flotation statements are true and supported by the design.The vessel aligns with the intent of AS 1799.1:2021.Wavemaster provides design data to assist with this process with every kit, but the final responsibility always rests with the builder.

Hull Identification Number (HIN)

What Is a HIN?

A Hull Identification Number (HIN) is a unique, permanently affixed identifier assigned to a recreational vessel.It serves a similar purpose to a VIN on a vehicle and is used to:Identify the vessel for registration and compliance.Link the boat to the builder and year of manufacture.Assist with theft prevention and traceability.A HIN is separate from the Builder Plate, but both are required for legal use and registration of a completed boat.

Who Is Responsible for the HIN?

For kit boats and DIY builds, the person who completes the boat is considered the builder and is therefore responsible for:Obtaining the HIN.Permanently marking it on the hull.Ensuring it matches the builder details shown on the Builder Plate.The kit supplier does not supply the HIN.

How to Obtain a HIN

Before completing the boat you need to contact a local HIN supplier. There is a requirement to mark a second HIN in a secret location which is recorded on the form so it's a good idea to arrange this early in the build while you have access to a suitable secret location.

Basic vs Level Flotation (Overview)

Australian standards recognise different flotation outcomes depending on vessel size, type, and use.

Basic Flotation

The vessel remains afloat when swamped.May float at an angle.Some parts of the hull may be submerged. The boat may be floating upside down.

Level Flotation

The vessel floats approximately level when swamped.Critical areas (such as the cockpit) remain more accessible.Typically recommended for smaller boats intended for general recreational use.Not all boats are required to have level flotation, and not all hull forms are suited to it. The correct approach depends on size, layout, displacement, and intended use.

Important Warning on Level Flotation and Real World Behaviour

Level flotation calculations are based on static, calm-water assumptions and do not represent how boats are typically swamped in real operating conditions.
In practice, boats are most often swamped due to waves, following seas, or dynamic events, not while stationary in flat water. These real-world conditions introduce forces that are not reflected in flotation calculations alone.

Free Surface Effect and Vessel Stability

When a boat with a sealed deck is swamped, water on the deck creates a free surface moment. This free surface significantly reduces stability and will often cause the vessel to heel or roll over, regardless of theoretical flotation volume.As a result, a swamped vessel is unlikely to remain upright and level in real sea conditions.

Foam Location in Sealed-Deck Boats

In boats with a sealed deck:Buoyancy foam located below the deck provides little or no benefit during a deck-level swamping event.The foam only becomes effective if:The hull is breached (not a required test condition), orThe vessel rolls over, which is when a sealed deck is more likely to leak.It is important to understand that under-deck foam does not prevent instability or capsize during a swamping event. In simple terms, if the foam remains dry it's not doing anything.

Our Position on Level Flotation Certification

The term level flotation can create an unintended perception of safety that does not align with real-world behaviour, particularly for sealed-deck aluminium boats.For this reason:Wavemaster does not certify sealed-deck boats as being designed for level flotation.
This position reflects:The limitations of theoretical flotation assumptions.The effects of free surface water on stability.The actual behaviour of swamped boats in real sea conditions. How the general boating community might interpret the term level flotation.

Important Notes for Kit Builders

A kit supplier is not the builder.Adding structure, tanks, cabins, equipment or fit-out that changes the vessel’s final characteristics may affect the compliance with the standard.Builder Plate values must reflect the as-built condition, not the bare hull.Incorrect or unsupported builder plate data may expose the builder to liability. Boat kits designed before 2021 may not comply with the requirements of AS1799.1:2021.

How Wavemaster Helps

Wavemaster hulls are professionally designed to the 2021 edition of AS1799.1, ensuring that your aluminium boat kit is up to date and current. We supply the data required for the plate with supporting calculations. We supply a pre-printed builders plate and HIN plates with every kit.

Further Reading & References