Clear height, door sizes and truck access: B-doubles vs rigid trucks

By Brenscot Builders | Last reviewed September 2026

Ask ten businesses what they want in a warehouse and most will say more height and bigger doors. Ask which trucks they actually run and the answers vary widely. That second question matters more, because the vehicles set the door sizes, the hardstand depth, the gate position and, often, whether a site works at all.

This article sets out the heavy vehicle dimensions that matter, how they drive the design, and why clear height is a fire compliance decision as much as a storage one.

The short answer

Start with the largest vehicle that needs to enter the site and design the access, doors and hardstand around it. Rigid trucks suit most lots. Semi-trailers need deeper aprons and wider entries. Full-length B-doubles, at up to 26 m long, need an approved road route to the site and considerably more space. Set clear height from your racking and equipment, then check it against the National Construction Code (NCC) fire compartment volume limits before it is fixed.

Start with the vehicle

Heavy vehicle dimensions are regulated under the Heavy Vehicle National Law, administered by the National Heavy Vehicle Regulator (NHVR). The general limits are:

The general width limit is 2.5 m and the general height limit is 4.3 m, with 4.6 m allowed for certain vehicles such as livestock and multi-deck car carriers.

Note: the Heavy Vehicle National Law was amended on 1 August 2026. The NHVR advises that the changes include increasing the general access length from 19 m to 20 m for some combinations, including prime mover and semi-trailer combinations, subject to conditions about trailer braking and side underrun protection. B-double lengths and the 4.3 m general height limit did not change. If you are designing for semi-trailers, allow for the longer vehicle.

Two points follow from the table.

Full-length B-doubles can't go everywhere. A B-double longer than 19 m is a restricted access vehicle and may only use routes approved for B-doubles. Short B-doubles of up to 19 m have general access. Before buying or designing a site for B-double access, check the NHVR Route Planner to confirm that approved routes reach the property, including the last few hundred metres through the estate. Estate roads and intersections are not always approved or physically suitable.

Industrial zoning does not guarantee truck access. Many SEQ lots work well for rigid trucks and semi-trailers, but cannot accommodate a B-double without giving up parking, landscaping or stormwater treatment area.

Turning paths and hardstand

The civil or traffic engineer tests the site layout with swept path analysis, using the design vehicles in AS 2890.2 (Off-street commercial vehicle facilities) and the Austroads Design Vehicles and Turning Path Templates. The Austroads templates include an 8.8 m service vehicle, a 12.5 m single unit truck, a 19 m prime mover and semi-trailer, and 25 m and 26 m B-doubles. Council planning schemes and their policies commonly nominate the design vehicle for a development, and commonly require service vehicles to enter and leave the site in a forward gear. Check the scheme for your council.

What this means on site:

• Rigid trucks turn tightly and suit smaller lots and shared multi-unit driveways
• Semi-trailers reversing to a door or dock need a deep apron. The length of the vehicle plus room to swing the prime mover sets the hardstand depth in front of the doors
• B-doubles generally work best with a drive-through or loop arrangement. Reversing a B-double is slow and needs a lot of room
• Entries and gates must be wide enough for the swept path, set back far enough that a truck waiting at the gate is clear of the road, and positioned where the council will approve a crossover
• Pavement where heavy vehicles turn tightly should be concrete. See hardstand options

Door sizes

Roller doors and sectional doors are made to order, so size them for the operation.

• Height. A door that trucks drive through must clear the tallest vehicle, which is 4.3 m for general access vehicles and 4.6 m for some, plus allowance for the apron grade and for the vehicle rocking as it crosses the threshold. Doors used only by forklifts can be lower, but check the mast height with a raised load.
• Width. Allow for the vehicle plus mirrors and a margin for approach angle. A door approached on a turn needs to be wider than one approached square.
• Number and position. Several well-placed doors usually serve an operation better than one very large one, and allow a unit to be divided later.
• Wind rating. Large doors are significant wind-loaded elements and their wind rating must suit the site. AS/NZS 4505 (Garage doors and other large access doors) is the Australian standard in this area, but its scope covers openings up to 3 m high, so the taller doors used on many warehouses fall outside it. For those, ask the supplier what the door has been designed and tested to, and have the engineer confirm it against the site wind classification.
• Dock or ground level. Recessed docks and dock levellers suit high-volume palletised freight from semi-trailers. Ground-level doors with forklift unloading suit mixed and smaller operations. Docks cost more and fix the use of that part of the site.

A roller door is not a fire exit. Under NCC clause D3D24, a doorway that serves as a required exit must not be fitted with a roller shutter or tilt-up door. The only exception is a Class 6, 7 or 8 building or part with a floor area of no more than 200 m2, where the doorway is the only required exit and the door is held open whenever the building is occupied. Apart from that small-building exception, a warehouse needs separate personnel exit doors, positioned to meet the NCC's travel distance limits. Plan them with the racking layout so they are not blocked.

Clear height

Clear height means the unobstructed height from the floor to the lowest overhead obstruction in the storage area. That is usually the underside of the rafter haunch at the wall, but it can be a light fitting, a sprinkler pipe or a crane beam. It is always less than the eave height or ridge height quoted on a plan, so be specific about which one you mean.

Set clear height from the operation:

• The top beam level of the racking, plus the load on it, plus lift-off clearance
• The forklift or reach truck's maximum lift and mast height
• Clearance beneath sprinkler heads, if the building is sprinklered
• Any mezzanine, crane or tall plant

Then check the fire consequences before fixing it.

Volume limits. Under NCC 2022 Table C3D3, a Type C warehouse fire compartment is limited to 2,000 m2 and 12,000 m3. At an average internal height of 6 m, a 2,000 m2 compartment is exactly 12,000 m3. Any higher and the volume limit is reached before the area limit: at a 10 m average height, a single compartment reaches the volume limit at 1,200 m2 of floor area (12,000 divided by 10).

Storage height. Under clause E1D13, storing more than 1,000 m3 of combustible goods higher than 4 m, in a compartment over 2,000 m2 or 12,000 m3, triggers a sprinkler requirement.

So extra height is never free. It adds wall and structure cost, and it can change the fire strategy for the whole building. See construction Types A, B and C and fire services.

Awnings over doors add to the picture as well. See awnings and fire compartment volume.

A checklist for your brief

1. The largest vehicle that must enter the site, and how often
2. How vehicles will load and unload: reverse to door, drive through, dock or ground level
3. Forklift type and maximum lift height
4. Racking height now, and what a future tenant or buyer might want
5. Whether containers will be handled on site
6. Number of car parks needed for staff and visitors, which competes with truck space

Frequently asked questions

What clear height does a warehouse need?

It depends on the racking and equipment. Work out the top load height plus clearances, then confirm the fire compartment volume and sprinkler consequences before settling on a figure.

How big should a warehouse roller door be?

Large enough for the tallest and widest vehicle or load that will pass through, with margin. For trucks, that means clearing the 4.3 m general vehicle height limit (4.6 m for some vehicles) plus an allowance for grades and movement.

Can a B-double access my industrial site?

A 25 m or 26 m B-double can only reach your site if an approved B-double route runs all the way to it and the site has the room. Check the NHVR Route Planner first, then have an engineer test the swept paths.

How long is a semi-trailer or B-double?

A prime mover and semi-trailer is up to 19 m, or 20 m where the conditions introduced in August 2026 are met. Full-length B-doubles are 25 m, or 26 m where conditions are met.

Can a roller door count as an exit?

Not as a required exit, except in a part of no more than 200 m2 where it is the only required exit and is held open while the building is occupied. Other warehouses need separate personnel doors, normally hinged doors, for egress.

Sources

• National Heavy Vehicle Regulator: mass and dimension limits; common heavy freight vehicle configurations; Heavy Vehicle National Law changes from 1 August 2026; Route Planner, nhvr.gov.au
• Austroads, Design Vehicles and Turning Path Templates, edition 4.0 (2023)
• AS 2890.2 Parking facilities: Off-street commercial vehicle facilities
• AS/NZS 4505 Garage doors and other large access doors
• National Construction Code 2022, Volume One: clause D3D24; Table C3D3; clause E1D13, ncc.abcb.gov.au

General information only

This article is general information, current as at September 2026. It is not traffic engineering, design or certification advice. Vehicle access, swept paths and fire compliance for your site must be confirmed by the relevant engineers and your building certifier.

Planning an industrial warehouse?

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