HIA or Master Builders.
The form you sign is the one that governs.

The Housing Industry Association and the Master Builders Association are the two largest residential building industry bodies in Australia, and each publishes a suite of standard-form building contracts for its members. Between them they account for a large share of the residential contracts signed in the country, which is why the question of how they compare comes up on almost every builder’s desk at some point.

The honest starting point is that both are good. Both are professionally drafted, both are written to comply with the domestic building legislation of the state they are used in, and both cover the same territory that any residential contract must. The differences are real but they sit in the detail, the wording, the definitions, the notice periods, the exact mechanics of a variation or an extension of time, rather than in one being sound and the other not. This page compares them at that level. The regulatory framework both sit inside is covered in the contracts reference, and the pricing structures they can carry are covered in building contract types and fixed price vs cost plus.

Why it matters

The choice matters less than most builders think, and the familiarity matters more. A builder who knows one suite thoroughly, its completion definition, its variation process, its notice periods, can run a job off the contract with confidence. A builder who switches between families job to job, or who never reads past the price and the dates, runs the job off habit and gets caught out when a marginal case turns on the exact wording of a clause they never studied. Everything here is general information, not legal advice, and the forms are revised regularly, so confirm the current version with the publisher.

Read together, the two suites are more alike than different in what they do, and different enough in how they do it that they cannot be treated as interchangeable.

For most builders the choice is settled by membership, access to each suite is generally tied to belonging to the body that publishes it, so a builder often uses the family of the association they are already a member of. Beyond that, the sensible driver is the job type, each suite has different forms for new homes, renovations, cost plus and small works, and the right one is the one drafted for the work actually being done.

The more important decision is to standardise. A builder who commits to one suite and learns it thoroughly gains something a builder who chops and changes never does, the ability to run the job off the contract’s actual definitions rather than off a general sense of how residential contracts work. When the completion definition, the variation formalities and the extension of time notice periods are the same familiar mechanisms on every job, they become tools the builder uses rather than traps that surface in a dispute. The point is less which family and more that the builder genuinely knows the one they use, in the state edition they use it, and runs the job off it deliberately.