Bathroom Renovation Quality Control: What to Inspect, When, and What Substandard Work Actually Looks Like
Most renovation defect complaints don’t start with a visible problem at handover. They start with a water stain on the ceiling below the bathroom six months later, or tiles lifting at the floor edge after the first winter, or a grout crack at the shower corner that’s been slowly channelling water behind the wall for two years. By that point, the tiler has been paid and moved on. What was a straightforward fix at practical completion is now a strip-out and re-tile.
That’s the problem this page is built around. Bathroom renovations fail in ways that aren’t visible when the job is signed off — and the conditions that cause those failures are almost always present from day one. Knowing what to look for, and when to look for it, is the difference between catching a defect while it’s cheap and discovering it once it isn’t.
Here’s what you need to know: the three inspection windows that matter, the failure modes most commonly found in residential bathroom renovations, how to read a practical completion sign-off, and what your options are when defects surface after the fact.
Why Most Bathroom Renovation Defects Don’t Show Up at Handover
Water damage, adhesive failure, and waterproofing breaches share one characteristic that makes them disproportionately expensive: they’re invisible from the finished surface. A bathroom can look completely finished — grout clean, silicone neat, tiles level — and be quietly accumulating moisture behind the tile bed. The renovation industry’s defect timeline breaks into two rough categories: cosmetic issues surface within weeks, substrate and waterproofing failures surface between six months and three years.
By the time a waterproofing failure becomes visible — staining on the ceiling below, mould tracking up the wall, tiles beginning to hollow — water has typically been moving behind the tile bed for months. What you’re seeing is the end of a process, not the beginning. Stripping tiles to get back to the membrane, replacing damaged substrate, reapplying waterproofing, and re-tiling costs multiples of what correct original installation would have. That cost difference is the reason inspection matters — not because tradies are all cutting corners, but because the work that prevents these failures happens before tiles go down and is invisible once they do.
This is worth distinguishing from cosmetic defects. An uneven grout joint, a silicone line applied unevenly, a colour mismatch on the sealant — these are annoying, they’re workmanship issues worth raising, but they’re inexpensive to fix if caught before final payment. Substrate and waterproofing failures are a different category. They’re cheap to prevent and expensive to remediate. The inspection approach that follows is weighted toward the things that matter most.
Two of the three meaningful inspection windows happen before the job is finished. That’s uncomfortable to plan around when you’ve hired a contractor to handle it — but a homeowner who only inspects at practical completion has already missed the moments when the most important work was accessible and visible.
Related: Most waterproofing failures aren’t visible from the surface. See our AS 3740 waterproofing compliance guide for what correct membrane installation looks like ›
Three Inspection Windows — and What Each One Covers
Inspection is not a single walkthrough at the end of the job. There are three points where the quality of the work is meaningfully assessable — and the leverage you have over the outcome decreases with each one. The earlier you look, the more you can actually influence.
Pre-tile — substrate and waterproofing
Before tiling starts. This is the highest-leverage point in the whole job: once tiles go down, what’s underneath is inaccessible for the next decade or more. What to look for: waterproofing membrane applied to a minimum 150mm upstand height on shower walls (AS 3740), no gaps or unbonded edges at corners and junctions, membrane fully cured before tiling commences, and substrate flat to the tolerance required by the tile format being installed. The waterproofer should be issuing a certificate of compliance at this stage. If they’re not offering one, ask for it in writing before tiling starts.
Mid-installation — adhesive coverage and movement joints
While tiling is in progress. Less commonly done by homeowners, but a site visit during installation is worth doing if you can. What to look for: back-buttering on large-format tiles (required under AS 3958 above certain dimensions), movement joints at internal corners and changes of plane being filled with silicone rather than grout, and consistent adhesive application. A quick test: ask the tiler to show you a tile they’ve just lifted for adjustment. The pattern of adhesive on the back of the tile is a reliable indicator of whether the bed is being applied correctly.
Practical completion walkthrough — before final payment
The last meaningful leverage point. Once final payment is released, the dynamic shifts — defects become a warranty claim rather than a contract issue. The walkthrough should document everything in writing before you sign: cosmetic and workmanship issues, any scope items not yet completed, and anything you’re uncertain about. Photographs with timestamps establish the condition of the work at the point of sign-off. Verbal agreements on the day aren’t worth much if the contractor later disputes what was said.
The practical implication of skipping these stages is straightforward: final payment gets released, the contractor moves on, and defects surface later when the conversation about rectification is slower, the legal process longer, and the repair more expensive. Most tradespeople doing good work have no issue with a homeowner asking to see the membrane before tiles go down. The ones who resist that conversation are telling you something.
The Defects Worth Knowing Before You Walk Through
These are the six failure modes most commonly found in residential bathroom renovations and most consistently missed at handover. Each one is described so you can identify it yourself on a walkthrough — no trade background required. They’re ordered by how quickly they present: the first few are visible in the first week, the last two take longer.
Hollow tiles
Tap across the tile field with a coin or your knuckle — methodically, not just a few spots. A hollow sound indicates an adhesive void: an area where the adhesive didn’t make contact with either the substrate or the tile back. Under AS 3958, the minimum adhesive contact in wet areas is 95% of the tile back. Getting there on large-format porcelain requires back-buttering — applying adhesive to the back of the tile in addition to the substrate. It’s time-consuming. When a job is under time pressure, this is often the step that gets skipped.
Not every hollow tile is an immediate structural risk. But hollow tiles are more vulnerable to cracking under load, and the adhesive void is an entry point for water if the tile surface is ever breached. Finding them at practical completion is a rectification conversation. Finding them six months later, after the grout has been sealed and the silicone has set, is a more expensive one.
Lippage
Run your hand across the floor tile joints. Lippage is the height difference between two adjacent tiles at their shared edge — visible as a raised lip when you drag a finger across the grout line. On a rectified tile installation, more than 1mm is a defect under Australian standards. The cause is almost always substrate flatness: the floor wasn’t prepared to the tolerance required by the tile format.
The fix after tiles are laid involves grinding the raised edge (which changes the finish and may void the tile warranty) or removing and re-laying. Before tiles go down, the fix is levelling compound — a fraction of the cost. If a tiler tells you the substrate doesn’t need levelling before a large-format installation, that’s worth pushing back on. It’s not a preference; it’s a specification requirement.
Grout at movement joints
Every internal corner in a tiled bathroom — floor-to-wall, wall-to-wall, and all changes of plane — is a movement joint. Buildings move fractionally with temperature, seasonal expansion, and load. Grout is rigid. Movement joints need flexible silicone sealant. Grout in a movement joint will crack. When, not whether.
The problem is that colour-matched sealant and colour-matched grout look identical at completion. Run a thumbnail along the internal corner of your shower base, where the floor tile meets the wall tile. If it’s rigid and doesn’t flex, it’s grout. That’s a rectification item. Water that finds that crack doesn’t stop at the surface — it tracks behind the tile bed, and if the waterproofing membrane has a joint in the same location, it finds a path through.
Covered in detail in our grout and sealants guide — specifically the bath-to-wall junction requirements under AS 3740.
Waterproofing upstand below compliant height
Under AS 3740, the waterproofing membrane on shower walls must run a minimum of 150mm up the wall from the floor. In a completed bathroom, you’re not going to be able to see where the membrane stops — it’s behind the tiles. What you can do is check whether a certificate of compliance was issued by the licenced waterproofer. That document is the evidence the upstand requirement was met. Without it, you’re taking the contractor’s word for it.
At pre-tile inspection, the membrane line is visible and this is easy to verify. At practical completion, the question becomes: where is the certificate? If the waterproofer didn’t issue one, or the contractor can’t produce it, that’s a gap in the documentation that’s worth resolving before you sign off.
Inconsistent grout joints
Step back from the tile field and look across it at a low angle — raking light makes inconsistencies easier to see than straight-on viewing. On rectified tiles, grout joint width should be consistent to within about half a millimetre across the whole field. Inconsistency indicates poor set-out, rushed installation, or a mismatch between the tile type and the specified joint width.
The distinction between rectified and non-rectified tiles matters here. Rectified tiles are cut to precise dimensions after firing. Non-rectified tiles have slight dimensional variation built in, which is why they require wider joints — to absorb the variation. Specifying a 2mm joint on a non-rectified tile and then expecting consistent lines is asking for an outcome the material can’t deliver. Worth confirming which type you’ve ordered before the tiler sets out.
Silicone condition at the bath junction
The bath-to-wall silicone joint is one of the highest-risk points in a bathroom. The bath flexes slightly under load — up to a couple of millimetres on a full bath. That movement needs to be absorbed by the flexible sealant at the junction. Silicone applied correctly here will flex with the movement. Silicone applied over residual grout, or applied too thinly, or applied without fully removing the tile spacers — won’t.
At practical completion, run a finger along the bath-to-wall line. It should be continuous, even in thickness, and adhered fully at both edges. A sealant line that’s lifting at the wall edge, or that has visible gaps, hasn’t bonded properly. This is an immediate sign-off issue. Getting the contractor to strip it and reapply before payment is straightforward. Getting them to come back and do it two months after final payment isn’t.
Important: A defect that’s visible at practical completion is inexpensive to address. One that’s been tiled over, grouted, and sealed isn’t — and by the time it’s visible from the finished surface, the repair cost has grown considerably.
What Practical Completion Actually Means — and What Signing It Doesn’t
Practical completion is one of those terms that sounds more definitive than it is. Most homeowners treat it as the moment the renovation is done and done. It isn’t. It’s the point at which the contracted works are substantially complete — the bathroom is functional and the major scope items have been delivered. Not defect-free. Substantially complete.
In NSW, the Home Building Act 1989 provides statutory warranties that operate independently of what you sign at practical completion. Signing the certificate doesn’t waive those rights. A contractor who tells you otherwise is either confused or hoping you are. The warranties — six years for major defects, two years for non-major defects — run from the date of practical completion regardless of what the contract says. They can’t be contracted out of.
The practical implication of this is that you should sign practical completion when the work is substantially complete, not hold out indefinitely over minor items — but you should do it with a documented defect list attached, not on a handshake. A written defect list that the contractor has acknowledged before you sign is enforceable. It records what was identified and what was agreed as outstanding, and it keeps the contractor’s obligation to rectify it clearly in the contract. A verbal “I’ll come back and fix that” on the last day of the job is not.
Before signing, request the waterproofing certificate of compliance if it hasn’t been provided. This is a document the licenced waterproofer should issue as a matter of course — it’s evidence that the membrane was applied to standard. If it’s missing at practical completion, add it to the defect list. Once you’ve signed and paid, getting documentation you didn’t ask for is harder.
Related: Practical completion connects to occupation certificates and final inspection requirements. See our permits and certificates guide ›
Before You Sign Off: The Practical Completion Walkthrough
Twelve things to check before releasing final payment. Not everything — a licenced building inspector working to a formal defect schedule covers more ground — but the items most consistently missed on homeowner walkthroughs and most expensive when they are. Take photographs as you go. They’re timestamped evidence of the work’s condition at sign-off.
Tap test — full tile field
Use a coin or knuckle on every tile in the shower enclosure and across the floor. Document the location of any hollow sounds before the contractor leaves site.
Internal corners — silicone confirmed, not grout
Every floor-to-wall and wall-to-wall internal corner in the shower should be flexible silicone. If it’s rigid and colour-matched to the grout, it’s grout. That’s a rectification item.
Bath junction seal — continuous and adhered
Run a finger along the bath-to-wall line. It should be even, continuous, and bonded at both edges. Gaps or lifting at the wall edge means it wasn’t applied correctly and needs to be stripped and reapplied.
Grout joint consistency in raking light
Step back and view the tile field at a low angle. Inconsistent joint widths on rectified tiles are a workmanship defect. Note locations before sign-off.
Waterproofing certificate of compliance
Request the certificate from the licenced waterproofer before signing. If it hasn’t been issued or the contractor can’t produce it, add it to your written defect list.
Shower floor drainage fall
Pour a cup of water onto the shower floor and watch it. It should run cleanly to the waste without pooling. Standing water in a shower base is a fall defect, not a maintenance issue.
Tapware and fixture seating
Tapware should sit flush and level against the tile face with no visible gap between the fitting and the tile. Gaps at penetration points are water ingress points.
Movement joints at changes of plane
Check floor-to-wall angles across the whole bathroom, not just in corners. Movement joints should also appear at regular intervals in large uninterrupted tile runs.
Lippage across floor tile joints
Run your hand across floor tile joints. More than 1mm height difference at any joint on a rectified tile installation is a defect. Note locations before signing.
Agreed defect rectifications — confirmed complete
Any items raised during the job that were agreed to be rectified before practical completion should be closed out and confirmed in writing, not verbally.
Cement grout sealed in wet areas
Confirm grout sealing has been completed, not deferred. It’s one of the steps most commonly left to the homeowner after payment, which means it often doesn’t happen at all.
Sealant colour as specified
Sealant colour should match what was agreed — not whatever was on the contractor’s van on the last day. Small detail, but a post-payment conversation about it is unnecessary.
Not Confident About What You’re Looking At?
Tell us what you’re seeing and we’ll connect you with a specialist who can review it properly.
Lifestyle Bathrooms is a referral and connector service, not a licenced contractor. We connect homeowners and property professionals in NSW and ACT with vetted bathroom renovation specialists.
Found a Defect. What Happens Next.
Before anything else: write it down. A defect that’s communicated verbally isn’t a documented defect — it’s a conversation that can be recalled differently by each party. An email to the contractor that identifies the specific defect, its location, and the rectification you’re requesting creates a paper trail that the subsequent steps all depend on. Photographs attached to that email establish the condition at the time of notification. Most reputable contractors will respond to a written defect notification without it needing to go further. The process below is for when they don’t.
In NSW, residential building work is covered by statutory warranties under the Home Building Act 1989. These aren’t contractual terms that can be negotiated away — they’re legislative minimums that apply regardless of what the contract says. The key warranties: work done with due care and skill, fit for purpose, and materials good and suitable. Major defects carry a six-year warranty from practical completion. Non-major defects carry two years. Whether a waterproofing failure or a substrate issue qualifies as a major defect depends on the extent of the impact — significant structural or waterproofing failure generally does.
Where the contract value exceeds the threshold requiring Home Building Compensation Fund (HBCF) insurance and the contractor holds a NSW licence, the HBCF provides a safety net for certain defect claims when the contractor can’t or won’t rectify. Eligibility conditions apply, and not every residential bathroom job is covered at HBCF threshold. Check through NSW Fair Trading before assuming coverage.
If the contractor disputes the defect or refuses to rectify, the NSW Civil and Administrative Tribunal (NCAT) handles residential building disputes. NCAT is accessible without legal representation for lower-value claims, though legal advice before lodging is worthwhile regardless of claim size. In the ACT, equivalent disputes are handled through ACT Civil and Administrative Tribunal (ACAT). The process in both cases: attempt direct resolution first, document the attempt, then lodge with the relevant tribunal if you can’t get a response. The documented paper trail from the first step is what makes the tribunal application straightforward rather than contested.
Related: Licencing obligations and statutory warranty responsibilities in NSW are administered by NSW Fair Trading. See our NSW Fair Trading licensing guide ›
Note: Lifestyle Bathrooms is a referral and connector service, not a licenced contractor. Nothing on this page constitutes legal advice. For disputes involving defective building work, seek independent legal guidance or contact NSW Fair Trading directly on 13 32 20.
Common Questions
The most reliable indicator at completion is the waterproofing certificate of compliance — a document the licenced waterproofer should issue as part of the job. It’s evidence that the membrane was applied to standard. If it’s not forthcoming, ask for it in writing before releasing final payment.
Once tiles are down, direct visual checks of the membrane are limited. What you can still assess: silicone is present (not grout) at all internal corners and junctions, there are no visible damp patches or staining on the underside of the bathroom floor if accessible from below, and the shower base shows no standing water after use.
Pre-tile is when the membrane is directly accessible and visible. If that window has passed, the certificate of compliance is the next best evidence. If neither is available, a licenced building inspector can conduct a moisture investigation — worth doing before a property purchase or if defects are suspected.
A defect is a failure to meet the standard of work that was contracted — the agreed specification, and the Australian standards that apply to the trade. Wear and tear is deterioration from normal use over time.
The practical distinction: silicone at a bath junction that starts lifting within two months of installation is a defect. Silicone that needs replacing after seven years of daily use is wear and tear. Grout that cracks in internal corners six months after a renovation is a defect — those joints should have been silicone. Grout that lightens with years of cleaning is normal.
The distinction matters for warranty claims. Statutory warranties under the Home Building Act 1989 cover defective work, not the normal lifespan of materials. A contractor who describes a premature failure as “normal wear and tear” is either confused about the standard that applies or hoping you are.
Generally, yes — final payment is typically conditional on practical completion, and a documented defect list can be attached to the practical completion process to establish what’s outstanding before payment is released. Review the payment schedule in your specific contract before withholding.
A more practical approach: sign practical completion with a written defect list that the contractor has acknowledged in writing. This preserves the payment relationship while establishing a formal record of what needs to be rectified. It’s more effective than withholding, which can trigger a dispute over the payment itself rather than staying focused on the defect.
If the contractor is pressuring you to sign and pay without a defect list, that pressure is a signal. The above is general process information — seek specific legal advice if you’re dealing with a contractor who is disputing the defects or your right to document them.
Under the Home Building Act 1989: six years for major defects, two years for non-major defects. Both periods run from the date of practical completion.
A major defect is one that affects the structural performance of the building, makes it uninhabitable, or makes it unfit for the purpose it was built. Significant waterproofing failure — membrane not applied correctly, upstand height below the AS 3740 requirement, sustained water ingress into the building structure — would typically qualify. Workmanship issues that don’t rise to that threshold fall under the two-year non-major category.
These warranties can’t be contracted out of. A contract clause that purports to limit them doesn’t override the legislation. If there’s any ambiguity about whether a specific defect qualifies as major, contact NSW Fair Trading or get independent legal advice before the relevant warranty period expires.
Start with a written notification — email with photographs attached, clearly identifying the defect, its location, and what rectification you’re requesting. Date it. Keep a copy. Most licenced tradespeople will respond to a written defect notification; the formal steps below are for when they don’t.
If no response or the contractor disputes the defect: contact NSW Fair Trading, who can provide guidance and facilitate a complaint. NSW Fair Trading also administers contractor licencing — if there’s a question about whether the contractor is appropriately licenced, that’s the place to check.
Unresolved from there: lodge with NCAT (NSW Civil and Administrative Tribunal). NCAT handles residential building disputes and is accessible without legal representation for lower-value claims. Legal advice before lodging is still worthwhile. In the ACT, the equivalent body is ACAT.
Keep all documentation throughout: the original contract, written communications at every stage, photographs with timestamps, and any quotes you obtain for remediation work. The quotes serve two purposes — they establish the cost of the defect and they’re often the catalyst for a contractor to come back to the table.