PERTHYour builder has to build the house that was approved
Work must match the approved plans. Building and Energy's Industry Bulletin 154, where builds depart from their approvals
Your builder has to build the house that was approved. Not a house like it, not a reasonable equivalent, not whatever the trades found easier on the day. The one on the stamped, approved plans. Building and Energy published Industry Bulletin 154 because this goes wrong often enough to warrant a reminder to the industry.
What "approved plans" means
When a building permit is granted, it is granted for a specific set of plans and specifications. That approved set is the legal description of what may be built. Departing from it is not a minor administrative matter — work that does not match the approved plans may not comply with the building permit, and in some cases may not comply with the building standards the plans were checked against.
Some changes are inevitable on a real site, and there is a proper way to handle them: the plans are formally amended and the amendment approved before the work is done. The problem is the change that is made quietly, on site, without that step, so that the finished building and the approved paperwork no longer describe the same house.
Where it shows up
Structural substitutions are the ones that matter. A different beam size than specified. A truss layout altered without the truss engineer signing off. A steel post left out because the opening "looked fine" without it. Bracing relocated or reduced. Each of these might be harmless, and each might not, and the only way to know is to check the built structure against the documents that were engineered for it.
Then there are the changes that are not structural but still matter: a wet area moved, a window resized, a room's use changed in a way that triggers different requirements. And there are the omissions — the specified item simply not installed, on the assumption nobody would compare.
The document trail you should have
A compliant build produces paperwork: the approved plans, the engineering details, truss layouts, and the inspection and compliance certificates for the stages that require them. You are entitled to that trail, and its absence is itself a finding. A builder who cannot produce the engineering for a change they made on site has told you how that change was decided.
Why this is a staged-inspection problem
The discrepancies that matter most are structural, and structure disappears. Once the frame is lined and the slab is poured, comparing the building to its approved plans becomes an exercise in demolition. At frame stage, it is an exercise in looking.
This is the strongest single argument for staged inspections on a new build. Checking the frame against the approved plans while the frame is still open is cheap. Discovering after handover that the beam over the open-plan living area is two sizes down from the one that was engineered is a different kind of problem, and a practical completion inspection can only catch what is still visible.
If it has already happened
Where a completed build departs from its approved plans and the builder will not resolve it, the matter can become a building service complaint to the Building Commissioner, and if it escalates, an expert witness question. The WA disputes process sets out the order things have to happen in. The report that supports such a claim has to compare what was built against what was approved, item by item, which is why the approved plans are the first document we ask for.
How work drifts from the approved plans
Building to the approved plans sounds like it should be automatic, the plans were approved, so the house gets built to them, but in practice work drifts from the approval for a range of ordinary reasons, and the drift is what creates the problem. Sometimes it is a deliberate variation the owner requested midway through, a room made larger, a window moved, a wall relocated, that was agreed with the builder but never formally taken back through the approval process. Sometimes it is a substitution the builder made, a material or a detail changed for availability or cost, that departs from what was specified. And sometimes it is simply an error, work set out or built wrongly and not caught. Whatever the cause, the result is a house that does not match the document it was approved against.
Most of the time these departures are minor and never cause trouble. But some of them matter, either because they affect the structural performance or compliance of the building, or because they create a mismatch between the physical house and its official record that surfaces later, when someone wants to renovate, sell, or check the approvals. Unapproved structural changes are the serious end: a beam resized, a wall removed, a footing detail altered, done without the engineering and approval that should accompany it, is a defect that a buyer very much wants to know about, because the consequences and the cost of regularising it fall on the owner.
Why this is a staged-inspection question above all
The reason building-to-plans is so closely tied to staged inspection is timing: the departures from the approved plans are visible while the work is being done and largely invisible once it is finished. At frame stage, an inspector with the approved plans in hand can see whether the frame matches them, whether the structural elements are where and what they should be, whether the openings and the layout correspond to the approval. Once the house is lined, clad, and finished, most of that is buried, and confirming that the concealed structure matches the plans becomes far harder and far more expensive. The stage inspections are the practical window in which building-to-plans can actually be verified.
This is why an owner who cares about getting the house they approved, rather than an approximation of it, is well served by independent inspection at the stages, checking the work against the approved plans while the checking is still possible. It is also why, on an existing house, evidence of departures from the original approval, or a mismatch between the building and its records, is something an inspection flags: it points to work that may not have been approved, which is a question a buyer needs answered before they take on the property and the responsibility for whatever was done to it.
What to do if the house does not match its records
Where a buyer discovers, or an inspection suggests, that a house departs from its approved plans or has work that does not appear in its records, the right response is neither to ignore it nor to assume the worst, but to establish the facts before committing. Unapproved work is not necessarily dangerous, but it is a liability: regularising it can be required, can be costly, and in some cases the work has to be modified or removed to gain approval retrospectively. The prudent path is to understand, through the appropriate professional and the relevant authority, what was done, whether it was approved, and what putting the records right would involve, so that the cost and the risk are known quantities before settlement rather than surprises afterward. A house that does not match its plans is a house with a question hanging over it, and the time to answer the question is before it becomes yours.
Getting what you approved
At its heart, building to the approved plans is about a simple expectation: that the house you end up with is the house you were approved to build, not an approximation of it shaped by unrecorded variations, quiet substitutions, and uncaught errors. Most departures are harmless, but the ones that are not, unapproved structural changes, work that creates a mismatch between the building and its official record, can carry real cost and real liability, and they fall on the owner. The practical protection is timing: verify the work against the approved plans at the stages where it is still visible, and establish the facts before committing to a house whose records and physical reality may not match. Whether you are building and want the house you approved, or buying and want to know that the house matches its paperwork, the principle is the same, and the window to act on it is before the work is buried or the purchase is settled.
Common questions
Does my builder have to follow the approved plans exactly?
Building work must comply with the approved plans. Changes should be formally amended and approved before the work is done; an unapproved departure may not comply with the building permit.
What if my house wasn't built to plan?
Where a completed build departs from its approved plans and the builder will not resolve it, the matter can become a building service complaint to the Building Commissioner and, if it escalates, an expert witness question.
When can this be checked?
Most easily at frame stage, before structure is concealed. After lining and pouring, comparing the building to its approved plans becomes far harder.
This comes up on every building stage inspections we carry out.
Read next: the name on the sign may not be the business building your house and how many houses is your builder running at once?.
Sources
Read rather than recalled. Summarised here; the documents themselves are Crown copyright and are linked rather than reproduced.