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Glossary of prefab and modular housing terms

From Modular Living Australia — the independent knowledge base Last updated: 8 Oct 2026

Australian prefab and modular housing borrows vocabulary from three separate systems — the building code, state planning law, and the road transport rules — and then adds its own trade shorthand on top. A quote can contain a dozen terms that have precise legal meanings and a dozen more that mean whatever the company writing the quote wants them to mean. This page separates the two.

Entries are grouped by subject rather than listed alphabetically, because the terms only make sense in relation to each other. Where a term has its own guide on this site, the guide is linked.

Building code terms §

The National Construction Code (NCC) sets the minimum technical requirements for new building work across Australia and is published by the Australian Building Codes Board. It groups buildings by use, and assigns each group a classification that is then used throughout the code.^[1]

Class 1a

A single dwelling — a detached house, or one of a group of attached dwellings such as a town house or row house. Most modular homes, transportable homes and granny flats used as permanent dwellings are Class 1a. A Class 1 building cannot sit above or below another dwelling, other than a private garage.^[1]

Class 1b

A boarding house, guest house or hostel with a total floor area under 300 m² ordinarily housing fewer than 12 people. It also covers four or more single dwellings on one allotment used for short-term holiday accommodation — the classification that often applies to cabins in holiday parks.^[1]

Class 2

An apartment building — typically a multi-unit residential building where people live above and below each other.^[1]

Class 10a

A non-habitable building: a private garage, carport, shed or similar. A structure approved as Class 10a is not approved for anyone to live in, which is why some studios and "backyard rooms" are sold without a kitchen or bathroom.^[1]

Class 10b

A non-habitable structure: a fence, mast, antenna, retaining wall, free-standing wall or swimming pool.^[1]

Class 10c

A private bushfire shelter, associated with a Class 1a dwelling.^[1]

AS 2870 is the Australian Standard for residential slabs and footings. The NCC requires that the foundation where a footing is to be located be classified in accordance with it.^[2]

AS 3959 is the Australian Standard for construction of buildings in bushfire-prone areas. It defines the Bushfire Attack Levels described below.^[3]

Deemed-to-Satisfy refers to a solution that follows the prescriptive route set out in the NCC. The alternative is a Performance Solution, where a designer demonstrates by other means that the code's performance requirements are met. Off-site construction sometimes relies on Performance Solutions where the code's prescriptive text assumes on-site building.

Construction methods §

The distinction that matters commercially is whether the factory ships flat pieces or finished three-dimensional boxes. Almost everything else — cost, transport, crane requirements, approval pathway — follows from it.

Volumetric modular

Complete three-dimensional modules built in a factory, including internal linings, cabinetry and often fixtures, then transported and craned into position. The most finished method, and the one with the heaviest transport and lifting requirements. See what is a modular home.

Panelised

Walls, floors and roof elements manufactured flat and assembled on site. Panelised and componentised systems made up just over half of Australia's prefabricated-buildings market in 2025.^[5] See what is a prefabricated home.

Componentised

Individual manufactured elements — trusses, wall frames, bathroom pods — supplied into an otherwise conventional site build. Most Australian homes already contain componentised prefab, usually roof trusses.

Flat-pack / kit home

A package of pre-cut and pre-labelled components delivered for assembly on site, sometimes by the buyer or a local builder rather than the supplier. Not covered by a dedicated guide on this site yet.

Structural insulated panel (SIP)

A sandwich panel with an insulating core bonded between two structural facings, used as a wall, floor or roof element. See SIPs in Australian homes.

Transportable / relocatable

A factory-built home engineered so it can be moved after installation. The distinction from modular is intent: a modular home is designed to be assembled once, a transportable home to be lifted again. See transportable and relocatable homes.

Tiny house on wheels

A compact dwelling built on a road-registrable trailer. To travel without special permits it must stay within road limits of about 4.3 m height, 2.5 m width and roughly 9 m length; Australian tiny homes are typically 15–55 m².^[6] See on wheels or fixed foundation.

Planning and approval terms §

Planning law is state law, so these terms do not mean the same thing everywhere. The definitions below note the jurisdiction where the term is specific to one.

Development application (DA)

The full council assessment pathway. A planning officer assesses the proposal on its merits, neighbours may be notified, and timeframes are open-ended.

Complying development / Complying Development Certificate (CDC)

A fast-track pathway for proposals that meet every one of a set of prescribed standards. Assessment is a compliance check rather than a merit judgement, and can be issued by a private certifier. In NSW a 60 m² secondary dwelling on a lot of at least 450 m² can qualify; flood, heritage or bushfire constraints push the proposal back to a full DA.^[7] The NSW Department of Planning states that complying development approvals can be issued in as little as 20 days.^[8] See do you need council approval.

Secondary dwelling

The planning term for a granny flat: a self-contained dwelling on the same lot as a principal home, with its own entrance, kitchen, bathroom and living area. In NSW it cannot be sold separately from the main title.^[9] See what is a granny flat.

Construction certificate / building permit

The approval confirming that construction drawings comply with the NCC. Separate from planning approval, and named differently in each state.

Occupation certificate

The document confirming a completed building may lawfully be occupied. For an off-site build it is issued after the modules are installed, connected and inspected on site — not when they leave the factory.

BASIX

The NSW sustainability assessment applied to residential development. NSW uses BASIX rather than NatHERS as its compliance pathway; BASIX adopted a 7-star-equivalent minimum in late 2023.^[4]

Energy, bushfire and climate ratings §

NatHERS

The Nationwide House Energy Rating Scheme, which rates the thermal performance of a home's building shell on a scale to 10 stars. Under NCC 2022 new houses must meet 7 stars.^[4]

Whole of Home

The second NCC 2022 requirement, covering fixed appliances and systems rather than the shell. New houses must meet a Whole of Home rating of 60 out of 100; new apartments must average 7 stars with no apartment under 6 stars, plus a Whole of Home rating of 50.^[4]

State adoption dates

Adoption of the NCC 2022 energy provisions is a matter for each state and territory. NSW adopted a 7-star BASIX minimum in late 2023, the ACT in January 2024, Victoria and Queensland from 1 May 2024, South Australia from 1 October 2024^[4] and Western Australia from 1 May 2025.^[10] Tasmania and the Northern Territory are not covered by the sources compiled here.

Bushfire Attack Level (BAL)

A measure of a building's potential exposure to ember attack, radiant heat and direct flame contact, expressed in kilowatts per square metre. AS 3959:2018 sets six levels: BAL-LOW, where risk is insufficient to warrant specific construction requirements; BAL-12.5, up to 12.5 kW/m² with ember risk; BAL-19, up to 19 kW/m²; BAL-29, up to 29 kW/m²; BAL-40, up to 40 kW/m² with an increased likelihood of flame contact; and BAL-FZ, the Flame Zone, above 40 kW/m² with direct exposure to flames.^[3] Builders commonly advertise a BAL rating their product can be built to; the rating that applies to a particular block is determined by assessment of that block.

Cyclonic rating

Design for the wind regions covering much of northern Australia. Several builders in the directory publish cyclone ratings; the applicable wind region for a site is set by the relevant standard and assessed for that site.

Site and delivery terms §

Site classification

The AS 2870 class assigned to a block based on how much the ground is expected to move. The classes are A (stable, non-reactive), S (slightly reactive), M (moderately reactive), H1 and H2 (highly reactive), E (extremely reactive) and P.^[11] The NCC requires the foundation to be classified before footings are designed, and sites classified E or P must be referred back to AS 2870 for design information.^[2] See site works and site costs.

Class P site

A site with conditions requiring site-specific engineering judgement rather than a standard footing design. It does not mean the site cannot be built on.^[11]

Cut and fill

Excavating the high side of a sloping block and using the spoil to build up the low side, to create a level building platform.

Craneage

The lift that places modules on their footings. Published guidance puts crane hire at roughly A$260–$1,530 per hour with four to ten hour minimums, and notes that remote or complex lifts can push delivery-day totals to roughly A$23,000–$30,600.^[12] These are builder-published commercial figures, not independent survey data.

Oversize overmass (OSOM)

Formally a Class 1 load-carrying vehicle under the Heavy Vehicle National Law: a vehicle that, together with its load, exceeds prescribed mass or dimension limits and is carrying a large indivisible item — one that cannot be divided without extreme effort, expense or risk of damage.^[13] A finished module is a textbook large indivisible item. See delivery, transport and craneage.

Pilot and escort vehicles

Vehicles required to accompany an oversize load under permit conditions. Whether they are needed, and how many, depends on the dimensions and the route.

Over-dimensional load permit

The state-level permit for moving a load beyond standard limits. Victoria advises allowing a minimum of 15 business days between lodging an application and the planned move.^[14]

Contract and quoting terms §

These have no statutory definitions in most contexts, which is precisely why they cause disputes. Treat every one of them as a question to ask rather than an answer to accept.

Turnkey

Marketing shorthand for a package the buyer can move into on completion. What it actually includes varies widely between companies. See what "turnkey" actually includes.

Base price

The advertised price for a standard design, generally before site works, transport, craneage, service connections and approvals. Published cost guidance notes that transport and installation are sometimes included only within a set radius of the factory.^[12]

Provisional sum (PS)

An allowance in a contract for work whose cost is not yet known — most often site works, before the soil report is in. If the actual cost exceeds the allowance, the buyer pays the difference.

Prime cost (PC) item

An allowance for a specified item not yet selected — taps, tiles, appliances. Same mechanism as a provisional sum, applied to products rather than work.

Inclusions and exclusions schedule

The itemised list of what a quoted price does and does not cover. The single most useful document for comparing two quotes, and the one most often omitted from a headline price.

Progress payments

The staged payments a buyer makes as construction advances. Off-site construction complicates the standard structure, because much of the value is created in a factory rather than on the buyer's land. See financing a modular home.

Defects liability period

The period after handover during which the builder is contractually obliged to rectify defects. Separate from, and usually shorter than, statutory warranty periods, which vary by state.

Organisations and acronyms §

ABCB

Australian Building Codes Board — the body that publishes the National Construction Code.^[1]

prefabAUS

The industry association for Australian off-site construction. It projects that 10% of Australian homes will be prefabricated by 2030, against prefabrication currently sitting at roughly 5% of the construction market.^[15] Its member directory is one of the sources behind this site's builder directory.

NHVR

National Heavy Vehicle Regulator — administers heavy vehicle access permits, including the oversize overmass permits used to move modules.^[13]

QBCC

Queensland Building and Construction Commission — the Queensland building regulator and licensing authority. Queensland licence numbers published by builders begin with a QBCC reference.

BPC

Building and Plumbing Commission — Victoria's building and plumbing regulator, established 1 July 2025 to replace the Victorian Building Authority (VBA).

VBA

Victorian Building Authority — the former name of Victoria's building regulator, replaced by the Building and Plumbing Commission (BPC) on 1 July 2025. See BPC.

NSW Fair Trading

The NSW regulator responsible for builder and contractor licensing.

NatHERS

Nationwide House Energy Rating Scheme — see the energy section above.^[4]

Terms not covered here §

Where a term is used inconsistently across the industry and no authoritative published definition exists, it is deliberately absent from this page rather than defined by inference. That includes company-specific product names, and marketing categories such as "eco pod", "granny pod" and "studio", which describe no fixed legal or technical class. If a quote uses a term you cannot find here, ask the company which NCC building class the finished structure will be approved as — that answer is definitive in a way the marketing name is not.

Standards Australia published SA HB 268:2026 Prefabricated Building — Glossary of Terms in 2026, developed by committee BD-111 at the request of the ABCB. It is the first nationally coordinated glossary for this sector, but it is not part of the NCC and sets no mandatory definitions, so the terms above follow common Australian usage rather than that handbook.^[16]

References §