Heavy Motorhome Certification: Everything You Need to Know

Converting a heavy vehicle into a motorhome should feel exciting, not stressful. Yet many owners only learn about certification rules after finishing their build. That delay often leads to expensive rework or even VicRoads rejection.
This guide gives you a clear, simple explanation of how heavy motorhome certification works in Victoria. It also highlights the rules from VSG5 and the VASS Newsletters, so you know exactly what to expect.

Why Heavy Motorhome Certification Matters

Heavy motorhomes (over 4.5 tonnes GVM) must meet Victoria’s engineering and safety rules before they can be registered. Engineers confirm this through a VASS Certificate or a VASS Letter, depending on the type of work done.
These documents show that your vehicle meets:

  • VSB6 modification codes
  • ADR requirements
  • NHVR rules
  • Motorhome safety standards listed in VSG5.

The July 2020 VASS Newsletter clearly states that VSG5 is a guide only and must not be used as a modification code. Therefore, the engineer uses VSB6 codes for structural work and VSG5 for motorhome features.

Three Certification Scenarios You Must Know

There are three situations for heavy motorhome certification. Understanding them will help you avoid confusion.

1. The bus is already converted and has structural modifications

For example: seat removal, new seat positions, or anchorages.

In this case, the engineer issues a VASS Certificate with:

  • the correct VSB6 codes (like K1)
  • the ADR category (NB2 or NC)
  • The body type listed as Mobile Caravan

Although VSG5 guides the safety check, it does not appear on the certificate as a modification code.

2. You remove or modify seats before the motorhome conversion

Many owners do this first.

Here, the engineer issues a VASS Certificate, but the body type often stays as Van until the motorhome fitout is complete.

3. The motorhome fitout needs checking, and structural work is already certified

If earlier VSB6 certifications exist, the engineer only checks the motorhome installation.

This situation requires a VASS Letter, not a certificate.
The letter confirms compliance with ADRs and with the guidance in VSG5.

What VSG5 Requires for Motorhome Conversions

The NHVR’s Vehicle Standards Guide 5 (VSG5) sets out the minimum safety requirements for heavy motorhome conversions. Each requirement helps ensure the motorhome is safe during travel and while parked.

Minimum motorhome features

A motorhome must include:

  • Seats and a table
  • sleeping accommodation
  • cooking facilities
  • storage

All of these must be securely fixed to the vehicle.

Doors

VSG5 requires at least one outward-opening or sliding door on the left side or rear. The inward-folding bus doors do not comply and must be replaced.

Ventilation

Good airflow is essential. Depending on the number of seats, the vehicle may need:

  • opening windows
  • roof vents
  • flow-through ventilation systems

Seats and seatbelts

Seat rules depend on how the motorhome is used:

  • Designated seats must match the number of sleeping berths
  • New or moved seats need VSB6 K1 certification
  • New seatbelts must meet current ADRs

Gas and electrical systems

Gas appliances must be installed by a licensed gas fitter.
Electrical systems that connect to mains power require a licensed electrician and certification to AS/NZS 3001.

Water systems, tanks, toilets, and showers

Fresh, grey, and black water tanks must be securely mounted.
Toilets must discharge into externally vented tanks.

Mass, GVM, tyres, and axle loads

VSG5 explains the importance of GVM, GCM, and correct weight distribution.
The VASS engineers must record manufacturer GVM/GCM and axle ratings, unless re-rating is being certified.

If tyres have a lower load rating than the axle rating, the engineer must note this on the certificate. However, the total tyre capacity must still be at or above the vehicle’s GVM.

Common Mistakes That Delay Certification

Motorhome owners often fall into the same traps. These mistakes appear across VSG5 and both VASS Newsletters:

  • Using VSG5 as a “mod code” (not allowed)
  • Keeping inward-folding bus doors (not compliant)
  • Installing new seats without VSB6 K1 approval
  • Poor ventilation or unsafe gas installation
  • Not considering weight distribution early.

A short consultation with an engineer can prevent all of these issues.

When to Speak With a VASS Engineer

Talking to an engineer early will save stress and money. You should contact one:

  • Before removing seats
  • before cutting, welding, or moving structural parts
  • before choosing doors or windows
  • before gas or electrical work begins
  • Any time you’re unsure about VSG5 or VSB6 rules

Early advice keeps your project compliant and avoids rework.

Your Simple Checklist for Heavy Motorhome Certification

Use this list before submitting your motorhome for approval:

  • VSB6 codes are used for any structural changes
  • VSG5 followed for motorhome fitout requirements
  • Correct use of the VASS Certificate or the VASS Letter
  • Outward-opening or sliding doors installed
  • Proper ventilation installed
  • Gas and electrical systems certified.
  • Seating and seatbelts comply with ADRs
  • GVM/GCM within limits
  • Body type set correctly (Mobile Caravan or Van)

With the right steps, certification becomes easier and more predictable.

Need Help With Heavy Motorhome Certification? ModiCert Can Help.

ModiCert specialises in VASS engineering, VSB6 approvals, and heavy motorhome certification across Victoria.
We guide you through every requirement from VSG5, the VASS Newsletters, and ADRs — and help you avoid expensive mistakes.

📞 Contact ModiCert today to get your motorhome certified smoothly and correctly the first time.

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