PERTHHow many houses is your builder running at once?
A registered builder must manage and supervise the work under their registration. Industry Bulletin 153, why thin supervision causes the defects that matter
You are paying a registered builder to build your house. A fair question, and one Building and Energy thought worth a bulletin of its own, is how many other houses that builder is running at the same time.
What supervision is meant to mean
Industry Bulletin 153 addresses management and supervision, and the principle behind it is simple: a registered builder is responsible for the building work carried out under their registration, and that responsibility includes actually managing and supervising it. It is not a signature on a permit and a set of subcontractors left to their own devices.
Supervision is how compliance is meant to happen in practice. Trades do their part; the builder coordinates them, checks the work at the points that matter, catches the error before the next trade covers it, and keeps the build aligned with the approved plans. Remove the supervision and each trade is working to its own understanding, which is how a house ends up built to nobody's plan in particular.
The problem the bulletin is really about
It is volume. One supervisor, dozens of sites. A supervisor running a handful can be across each of them. A supervisor nominally responsible for dozens, spread across the metropolitan area, cannot physically be at the right site at the right stage, and the supervision becomes a fiction maintained on paper.
The stages where supervision matters most are exactly the ones that are quick to pass and permanent once passed. A reinforcement error before a slab pour. A tie-down connection before the roof is clad. A waterproofing detail before the tiler arrives. Each has a narrow window in which a supervisor could catch it, and each is buried within days.
What you can actually do about it
You cannot audit your builder's whole workload, but you can do two things. Ask who the nominated supervisor is and expect a straight answer. And arrange your own eyes on the site at the stages that matter, independent of the builder's own supervision.
That second point is the entire case for staged inspections. An independent inspection at pre-slab, frame and pre-plaster does not replace the builder's supervision — it verifies it, at the moments when verification is still possible and still cheap. Where supervision has been thin, that is where it shows.
How this connects to everything else
Thin supervision is the common cause behind several of the specific failures covered elsewhere on this site: tie-down chains that stop partway, wet areas that leak, and work that departs from the approved plans. None of those is usually a mystery. They are what happens when nobody with the responsibility to check was there to check.
If it has already gone wrong, the questions of who was supervising and whether the work matched its approval are central to any expert report.
What a supervisor is actually responsible for
Understanding what site supervision is supposed to deliver comes before judging whether it is delivering it. The site supervisor is the builder's representative on the ground, responsible for coordinating the trades, keeping the work moving to program, and ensuring that what gets built matches the approved plans and meets the relevant standards. On a well-run site that is a genuine quality-control function: the supervisor catches the bricklayer who has set the articulation joint in the wrong place, notices the flashing lapped the wrong way before the cladding goes on, and holds a stage until it is right. The role exists precisely because construction is a sequence of trades each covering the last one's work, and someone has to be checking before each layer disappears.
The difficulty is structural rather than personal. The supervisor works for the builder, is often running several jobs at once, and is measured on keeping the program moving and the budget intact. Those pressures do not make supervisors dishonest, but they do mean the supervisor's attention is divided and their incentives are not purely aligned with your interest in every detail being right. A supervisor stretched across a dozen sites cannot give any one of them the sustained attention that catching every concealed defect would require, and the defects that get missed are, by definition, the ones nobody with time to look was looking for.
The gap an owner can actually close
Understanding the limits of the builder's supervision points straight at what an owner can do about it. You cannot supervise your own build, and you should not try, standing on a construction site second-guessing trades is neither safe nor useful. What you can do is commission independent inspections at the stages where a problem is still visible and still cheap to fix, so that a second set of eyes, answerable only to you, checks the work at the points that matter most. That is not a vote of no confidence in the builder; good builders welcome it, because a defect caught at frame stage is cheaper for them too, and a client who has had the work independently checked signs off at the end without a fight.
The stages that most repay this are the ones where something is about to be permanently concealed: the frame, where the whole structure and every tie-down is visible, and the pre-tile waterproofing check, which is the only practical chance to confirm the wet-area membranes before they are covered for the life of the house. An independent inspection at those points closes the gap between what the builder's supervision is incentivised to catch and what you actually need caught.
The document trail supervision should leave
Good supervision leaves a paper trail, and the presence or absence of that trail tells you something. A well-supervised build generates inspection records, sign-offs at the key stages, evidence that the waterproofing was checked before tiling, that the frame was inspected before lining, that the required certificates were obtained. When you take handover, asking for that documentation is reasonable, and a builder who can produce it is a builder whose supervision was doing its job. A build where none of that exists is not necessarily defective, but it is a build where the quality control was informal and unrecorded, which leaves you with less to rely on if a problem emerges later.
This connects to why independent staged inspection is worth the cost even on a build with a conscientious supervisor: it produces your own record, photographed and dated, of the condition of the work at each stage, held by someone who answers to you. If a dispute arises later, that independent record is a far stronger position than a vague recollection that the work looked fine, and it is the kind of documentation that turns an argument into a matter of evidence.
The honest summary for an owner
The honest position on site supervision is that it is real, it is valuable, and it is not enough on its own to guarantee your interests, because it is not designed to. The builder's supervisor is doing a genuine job, but it is the builder's job, run under the builder's pressures, and the parts of it that most affect you, the concealed structural and waterproofing work that gets covered before anyone independent looks at it, are exactly the parts where an owner benefits most from a second, independent check. Commissioning that check at the key stages is not a signal that you distrust your builder; it is simply recognising that the person whose money and future are on the line is you, and that a set of eyes answering to you, at the moments things get buried, is worth what it costs. The build happens once, and the parts that get covered stay covered for the life of the house, so the chance to check them does not come again.
Common questions
Does a registered builder have to supervise the work?
Yes. A registered builder is responsible for managing and supervising the building work carried out under their registration, which Industry Bulletin 153 addresses directly.
Why does supervision matter to the finished house?
The stages where errors are cheap to catch and permanent once passed — reinforcement before a slab pour, tie-downs before cladding, waterproofing before tiling — are exactly the ones a stretched supervisor misses.
This comes up on every building stage inspections and practical completion (pci) inspection we carry out.
Read next: the name on the sign may not be the business building your house and your builder has to build the house that was approved.
Sources
Read rather than recalled. Summarised here; the documents themselves are Crown copyright and are linked rather than reproduced.