PERTHInstallation: missing tie-downs, missing ant caps, off-plan work
The AS 4349.1 defect type for work installed badly, wrongly, or missing — the standard names missing tie-downs and missing ant caps
Some defects were built in. Not worn, not damaged, not deteriorated — wrong from the day the house was finished. AS 4349.1 calls these installation defects, and they are the category that most often points back to the builder, because they are what happens when work is done badly, used wrongly, or left out altogether.
What an installation defect is
AS 4349.1 Appendix F lists installation as a defect type covering components installed badly, used in the wrong application, or missing entirely. Crucially, the standard's own examples in Table F1 include missing tie-downs and structural connections, and missing ant caps. These are not degradation over time. They are things that should have been there and never were.
That makes installation defects different in character from the other five types. The others are usually about what the environment has done to a building. Installation defects are about what a person did, or failed to do, when it was built.
The ones that matter most in Perth
Missing or incomplete tie-downs. Named in AS 4349.1. The chain of straps and connections that holds a roof down against uplift, either absent or stopping partway. Building and Energy found a low level of compliance in roof frame construction across 123 WA dwellings it inspected. Covered fully in our tie-down guide.
Missing ant caps. Also named in AS 4349.1. The metal barriers over piers and stumps that force termites into the open where they can be seen. Their absence is an installation defect that undermines the whole termite management strategy.
Departures from the approved plans. Structural substitutions, omitted posts, altered bracing — work that does not match what was engineered and approved. This is its own guide, on building to approved plans, and it is where installation defects meet builder accountability.
Waterproofing done wrong. A wet area membrane installed incorrectly is an installation defect that becomes a water-penetration defect the first wet season. Covered in the wet-area guide.
Why these are often major
Because missing structural elements meet the clause 1.4.10 threshold directly — a roof without adequate tie-down is an unsafe condition waiting for the right wind, and a house without ant caps has lost a layer of protection against a defect that can compromise the structure. Installation defects also tend to be systemic: a builder who skipped tie-down on one connection often skipped it on others, so one finding warrants looking harder at the rest.
The advantage of catching them early
Installation defects are most visible before they are covered up, which is the entire argument for staged inspections. A missing tie-down at frame stage is a five-minute fix. The same defect found after handover is hidden behind linings and insulation. Where the house is already built, a pre-purchase inspection finds what remains visible, and a timber pest inspection catches the missing ant caps, because that is where they are looked for.
Why installation defects are so common
Installation defects are, in a sense, the most avoidable category, and that is exactly why they are so common. They are not the result of age, weather, or ground movement acting on a building over time; they are there from day one, built in by a component being fitted wrongly, in the wrong place, or not to the manufacturer's or the standard's requirements. A flashing lapped the wrong way so it channels water in rather than out. A tempering valve left off a hot water system. Insulation stuffed against a flue with no clearance. A downpipe that discharges against a wall instead of into the drainage. None of these developed; all of them were installed.
The reason they slip through is usually pressure and inattention at the point of installation rather than incompetence. A trade rushing to finish, a detail nobody checked, a component fitted by someone who did not read the requirement, a supervisor who did not catch it. On a new build in particular, the sheer number of individual installations, every fitting, every fixing, every connection, means that even a small error rate produces a handful of installation defects on almost any house, which is a large part of why an independent set of eyes at the construction stages is worth having.
The installation defects that carry safety consequences
Some installation defects are cosmetic or a matter of durability, but a subset carry genuine safety consequences, and those are the ones an inspection treats most seriously. Two WA-specific ones recur often enough to single out. Since 2009, a home offered for sale in Western Australia must have residual current devices covering all power and lighting circuits, and mains-powered smoke alarms are required on the same trigger; where these are absent or wrongly installed, that is an installation defect with a compliance and a safety dimension at once. Hot water delivered above the safe temperature, because a tempering valve was never fitted or has failed, is a scald risk, particularly in a house with children or elderly occupants.
Beyond those, installation defects in the things that manage water and fire tend to be the ones that matter most: waterproofing membranes in wet areas laid short or not turned up at the edges, flashings installed so they direct water into the structure, flue and heat-producing appliances fitted without the required clearances to combustible material. These are the installation errors whose consequences are not a stain on a ceiling but a genuine hazard or a structural problem down the line, and they are why the category is not just about tidiness.
Why they are cheapest to catch early
The defining feature of an installation defect is that it was wrong from the start, which means, in principle, it could have been caught the moment it was done. That is the whole argument for staged inspection on a new build. A flashing lapped the wrong way is a five-minute correction while the wall is open and before the cladding goes on; the same flashing found after the house is finished and leaking is a wall opened up and rebuilt. A waterproofing membrane that was not laid correctly is a quick re-do before the tiles go down and a bathroom demolition after. The defect is identical; the cost of fixing it multiplies with every stage of construction that goes over the top of it.
On an existing house, the installation defects are already buried, and the inspection's job is to find the evidence that reaches the surface, the stain that points to the flashing, the temperature at the tap that points to the missing valve, the cracking that points to the fixing that was never done. On a house under construction, the same defects are still visible, still cheap, and still correctable, which is why catching them is the entire economic case for inspecting the stages rather than only the finished result.
What the report does with an installation defect
Because installation defects were built in rather than developed, the report can usually be specific about both what is wrong and what putting it right involves, and it names the trade that owns the fix. A missing tempering valve is a plumber's job. A wrongly installed flashing is a roofer's or a builder's. An electrical compliance item is an electrician's. Where the defect carries a safety consequence, the report says so plainly and does not soften it, because an installation defect that is also a hazard is exactly the kind of finding that a buyer needs stated in clear terms rather than buried in a list. The value of separating installation defects out as a category is that it points at responsibility: these are things that were done wrong by someone, and knowing that shapes both the rectification and, on a recent build, the conversation with the builder.
Common questions
What is an installation defect?
Under AS 4349.1 Appendix F, it is a component installed badly, used wrongly, or missing entirely. The standard's own examples include missing tie-downs and structural connections, and missing ant caps.
Why are installation defects often major?
Because missing structural elements meet the major-defect threshold directly — a roof without adequate tie-down is unsafe in the wrong wind — and they tend to be systemic, so one finding warrants checking the rest.
This comes up on every building stage inspections and building & timber pest inspection we carry out.
Read next: your builder has to build the house that was approved and material deterioration: the defect Perth's coast accelerates.
Sources
Read rather than recalled. Summarised here; the documents themselves are Crown copyright and are linked rather than reproduced.