Bathroom Waterproofing in Strata: Leaks, Falling Tiles and the State-by-State Rules for 2026

The quick rule

Waterproofing failures are the single largest defect category in Australian apartment buildings. In NSW, waterproofing makes up around 42 per cent of all serious defects identified in Class 2 buildings.
The membrane under your bathroom tiles is usually common property in NSW, often common property in WA, sometimes common property in Victoria, and almost never common property inside an apartment lot in Queensland. Each state plays this differently.
A shower leak inside a lot may be the lot owner's plumbing, the lot owner's silicone, the owners corporation's membrane, or the original builder's defect, and the answer to "who pays" depends on which of those failed first.
Bathroom renovations in strata are not minor renovations in most states. In NSW they need a special resolution because they affect waterproofing. The same logic applies elsewhere.
New-build waterproofing has its own warranty regime. In NSW the limit is six years from completion for major defects. In Queensland the QBCC scheme covers structural waterproofing for around six and a half years. The clock starts the day the building is finished, not the day the leak appears.

This guide walks through the standards that govern wet-area waterproofing, why showers leak and tiles fall off, where the membrane sits on the lot–common property line in each state, the statutory warranty options when the building is new, and what insurance does and does not cover when the damage spreads. It is written for owners and committees who want to know what to do the morning the ceiling stain appears.

Why waterproofing is the biggest defect in Australian apartments

The numbers are uncomfortable.

The NSW Building Commission's research into serious defects in Class 2 buildings has consistently identified waterproofing as the number-one defect category, accounting for roughly 42 per cent of serious defects in surveyed buildings. CHU Underwriting Agencies reports that more than half of its residential strata claims relate to water damage. Strata Community Insure has paid out over 50 million dollars in water damage claims across a recent three-year window.

The economic logic is simple. A shower membrane fails quietly. Water moves through the screed, into adjoining lots, into ceiling cavities, into electrical fittings. By the time the stain reaches the ceiling below, the failure has been running for weeks or months. The repair touches multiple lots, multiple trades, and usually multiple insurance policies. The cost of fixing a 600 dollar membrane becomes the cost of stripping a bathroom, replacing tiles, restoring the ceiling below, and accommodating two displaced households.

The bigger problem is that the building's premium rises with every claim. A scheme with a recent history of waterproofing claims pays more for its strata policy at every renewal, and the additional premium is paid by every lot owner through levies. The economic incidence of one failed bathroom is shared across the whole building. This is why the most engaged committees treat bathroom waterproofing as a building-wide issue, not a private matter for the lot that happens to be leaking this week.

The standards that govern wet-area waterproofing

There are three documents committees and owners should be aware of.

AS 3740:2021: Waterproofing of domestic wet areas. The current edition, which replaced AS 3740-2010 in 2021. The 2021 edition introduced a three-tier risk classification: Category 1 (enclosed and unenclosed showers, the highest risk), Category 2 (bathroom areas outside the shower), and Category 3 (wet areas with no shower). The headline requirements include:

Shower walls must be waterproofed across the full water-resistant lining to a minimum of 1800 mm above finished floor level, or 50 mm above the shower rose, whichever is higher.
The floor of the shower area must be fully waterproof, with falls to the waste compliant with the standard.
Areas adjacent to the shower require a minimum fall of 1:100. Accessible bathrooms under the NCC Livable Housing Provisions require 1:80.
All penetrations, junctions, hobs and floor wastes must be sealed in accordance with the system manufacturer's specification.

AS 4654.1 and AS 4654.2: Waterproofing membranes for external above-ground use. This is the standard that governs balconies, roof terraces and planter boxes above occupied space. Apartment balconies are usually built to this standard, not AS 3740. The minimum fall is 1:100, with upturns of at least 100 mm at walls and 25 mm above the floor finish at door thresholds.

National Construction Code 2022, Volume One, Part F2: Wet areas and overflow protection. This is the operative section for Class 2 buildings. Specification 26 sets what must be waterproof versus water-resistant; AS 3740 dictates how. Shower floors must be waterproof, shower walls waterproof to the heights described above, and all wall–floor junctions, penetrations and hobs waterproof.

Who is allowed to do the work matters as much as how it is done. In NSW, waterproofing work valued over 5,000 dollars requires a contractor licence from NSW Fair Trading. In Queensland, the threshold is 3,300 dollars and the licence is issued by the QBCC. In Victoria, residential waterproofing over 5,000 dollars requires VBA registration. In WA, SA, Tasmania, the ACT and NT the picture is similar in shape (trade qualification, Certificate III in Construction Waterproofing, plus state builder or trade licensing) but the dollar thresholds vary. If the work is done by someone unlicensed, the building's insurance position and the lot owner's statutory warranty position both weaken substantially.

Why showers leak and tiles fall off

Most people imagine the membrane as the thing that fails. In practice, the failure usually starts somewhere else.

Silicone perishes first. Most modern silicones are rated to last around five to ten years in continuous wet exposure. Once the silicone fails at the wall–floor junction, water tracks into the screed and onto the membrane. The membrane often holds, but the water finds a penetration, a low spot, or a hairline crack and gets through.

Movement cracks in the screed. Buildings move. Slabs shrink. The bond breaker required by AS 3740 at the wall–floor junction is the standard's response to this: it allows the screed to move without tearing the membrane. Older installations did not always have a bond breaker, and the membrane tears slowly with each cycle of movement.

Failure at penetrations. Floor wastes, tap stems and shower screen anchors are the usual entry points. Each is a hole in the membrane that has to be sealed when it is installed and resealed when fixtures are replaced.

Tile delamination from efflorescence. Water that gets through grout sits on the membrane, dissolves salts out of the screed, and migrates back through the tile adhesive. The salts crystallise on the surface as white powder, and the adhesive bond degrades. Tiles loosen, sound hollow, and eventually fall. This is the most common visible warning that water is getting past the grout, long before there is a visible leak in the lot below.

Incorrect adhesive. Some tile adhesives are not rated for continuous wet exposure. A bathroom tiled with the wrong adhesive will delaminate within a few years even if the membrane is sound.

Membrane age. There is no regulated lifespan, but industry guidance and product warranties cluster around 10 to 15 years for a refresh point. A well-installed membrane in a low-traffic bathroom may last 20 to 25 years. A poorly installed membrane in a busy ensuite may fail in five.

Most bathroom waterproofing failures are not single events. They are slow degradations that produce a sequence of warning signs (perished silicone, efflorescence on grout lines, hollow-sounding tiles, a damp patch on a downstairs ceiling) before the catastrophic failure. The catastrophic failure is the moment the owner finally calls the strata manager. Everything before that was preventable.

Lot or common property: state by state

This is the question that determines who pays.

Almost every apartment in Australia is built so that the waterproofing membrane sits physically inside a lot. The legal question is whether the membrane is part of the lot or part of the common property. The answer changes between states, between plan formats, and sometimes between buildings within a single state.

New South Wales

The owners corporation has a non-delegable duty under section 106 of the Strata Schemes Management Act 2015 to maintain and repair common property. The membrane in a bathroom is widely accepted in NSW practice as common property: the tiles and grout are lot owner, the membrane underneath is the owners corporation's. The reasoning is that the membrane is a structural element of the building envelope, not a finish.

Section 106(5) gives a lot owner a statutory damages claim against the owners corporation if it breaches its duty to maintain. The limitation period for that claim was extended in 2016 from two years to six years from when the owner first became aware of the loss, confirmed in Vickery v The Owners – SP 80412 [2020] NSWCA 284 and applied in subsequent NCAT decisions. An owner whose downstairs ceiling has been damaged by a failed membrane upstairs has a direct claim against the owners corporation for the cost of repairs, regardless of whose insurance pays the building damage.

Bathroom waterproofing renovations are not "minor renovations" under section 110 of the SSMA 2015. Waterproofing is specifically excluded from that pathway. A bathroom renovation that affects waterproofing requires a special resolution (at least 75 per cent of votes) at a general meeting, not committee sign-off. Most schemes also pair the approval with a common property rights by-law transferring future maintenance of the new membrane to the renovating lot owner. Without that by-law, the next failure of the new membrane is back on the owners corporation.

Victoria

The position is less settled than in NSW. Under the Owners Corporations Act 2006, sections 46 and 129 require the owners corporation to maintain common property and the lot owner to maintain the lot. Where the boundary sits depends on the registered plan of subdivision.

In Owners Corporation PS508732B v Fisher [2014] VCAT 1358, the tribunal held that where a plan of subdivision defines lot boundaries by the interior face or median line of walls (almost universal in Victorian apartments), tiles and the underlying waterproofing membrane are private property. The Victorian Building Authority's wet-area fact sheet treats waterproofing as a building practitioner's compliance obligation but does not extend the owners corporation's maintenance reach into a lot.

The practical result in Victoria is that more bathroom waterproofing claims sit with the lot owner than in NSW. Committees should check the registered plan rather than assume the membrane is common property.

Queensland

The Body Corporate and Community Management Act 1997 and its module regulations govern, with the plan format doing most of the work.

Most Queensland apartments are registered on a Building Format Plan (BFP), where the lot boundary is the centre of the floor, wall and ceiling. In The Dalgety (Apartments) [2020] QBCCMCmr 118, an adjudicator confirmed that bathroom waterproofing in a BFP lot is wholly within the lot's boundaries and is therefore the lot owner's responsibility, not the body corporate's. This is the headline difference between Queensland and NSW. In a Queensland apartment, your bathroom membrane is your problem.

Balconies and terraces are a different matter. In Jefferson Villas [2024] QBCCMCmr 473, an adjudicator held that the body corporate was responsible for waterproofing a balcony terrace in an exclusive-use area, including the consequential costs of access and reinstatement. Balcony membranes in BFP apartments are usually body corporate responsibility because they form part of the building's external envelope.

Townhouse schemes registered on a Standard Format Plan (SFP) put far more on the lot owner. The body corporate maintains the common structures; everything inside the lot, including waterproofing, is generally the owner's.

Bathroom renovations in Queensland still need authorisation under the relevant module if they affect common property or improve a lot in a way that touches the body corporate's risk. Owners often miss this step and discover later that the body corporate cannot ratify the work after the fact without an owner contribution agreement.

Western Australia

The Strata Titles Act 1985, as amended in 2018 and 2020, defines common property as everything not within a lot. Where the lot boundary sits depends on the strata plan's boundary definition: median line, internal surface, or upper-surface conventions.

The State Administrative Tribunal has held in balcony cases (the most-cited example being Bennett) that where a part-lot balcony was defined to the upper surface of the tiles, the tiles and the waterproofing membrane below them were the strata company's responsibility. The same logic applies inside bathrooms where the plan's boundary definition puts the membrane on the common-property side of the line.

The practical step for WA owners is to read the strata plan itself, not the popular summary. Two buildings on the same street can have different boundary definitions and therefore different answers to the same leak.

South Australia

The Strata Titles Act 1988 and the Community Titles Act 1996 cover most SA schemes. Body corporate maintains common property; lot owner maintains the lot. The boundary is set by the deposited plan.

There is less reported case law on bathroom membranes in South Australia than in NSW or Queensland. The default approach is the same: check the plan, read the by-laws, and where the answer is unclear, get an opinion before the work starts rather than after the leak appears.

Tasmania

Under the Strata Titles Act 1998, the body corporate is responsible for common property as defined on the strata plan, and the lot owner is responsible for the lot. The NRE Tasmania strata living booklet (most recent edition June 2025) confirms the general framework and points owners to the registered plan for boundary specifics.

Most Tasmanian apartment schemes will treat the membrane similarly to NSW (common property in practice, even though the tiles are lot owner) but the answer depends on the plan boundary and any registered by-laws. Smaller schemes (two and three lot strata) sometimes have minimal by-laws, in which case the general maintenance obligations do the work.

Australian Capital Territory

The Unit Titles (Management) Act 2011 sets up the owners corporation framework. The default rules and any custom rules govern maintenance. ACT Planning publishes a practical guide for multi-unit residential building maintenance, which describes the typical division: the owners corporation maintains common property and structural elements, and the unit owner maintains the unit.

Where the unit plan defines the boundary at the interior face of structural elements, the membrane usually falls on the common-property side. The ACT Civil and Administrative Tribunal is the forum where unresolved disputes end up.

Northern Territory

The Unit Title Schemes Act 2009 and the older Unit Titles Act 1975 govern strata in the NT, depending on which legislation the scheme was registered under. The default rules and any custom rules apply, with the typical pattern being a maintenance allocation that follows the unit plan's boundary definitions. The NT has fewer apartment schemes than the larger states, and the practical decision-making often happens at body corporate committee level.

"My shower leaks, who pays?" A decision tree

The right sequence in any state is the same, even when the answers differ.

Stop the leak. Turn off the shower mixer, close the lot's isolation valve if necessary, and document the leak in writing to the strata manager or committee. Photograph the damage on both sides: the lot where the water is coming from and the lot where it is showing.
Identify the failed component. Engage a licensed plumber or waterproofer for an inspection. The sequence of typical findings runs: perished silicone (lot owner), failed grout (lot owner), failed tile adhesive or efflorescence (lot owner, but a strong indicator of underlying membrane failure), failed membrane (state-dependent, see above), failed common property pipework or structural waterproofing (owners corporation).
Match the component to the responsibility. Apply the state's rule. In NSW, almost any membrane failure is on the owners corporation. In Queensland, almost any bathroom membrane failure in a BFP apartment is on the lot owner. In Victoria and WA, the answer depends on the registered plan.
Notify insurance. Strata insurance handles the building damage; lot owner contents insurance handles the carpet, fittings, and contents of the affected lot. Both insurers should be notified within a few days, even before the repair scope is finalised, because most policies have notification windows.
Repair under the right authority. If the membrane is common property, the owners corporation arranges the repair and pays for it. If the membrane is lot owner, the owner arranges the repair under any required approvals (in NSW, a special resolution if waterproofing is being installed or replaced). If the building is young enough to be in warranty, the warranty claim is preserved by giving the builder notice; see below.

The expensive mistakes happen when steps 2 and 3 are skipped. Owners assume the leak is "the strata's problem", the committee assumes it is "the owner's problem", and three months go by while the membrane continues to leak. By the time the inspection actually happens, the cost has tripled.

"Tiles are falling off my shower wall, what do I do?"

Falling or hollow-sounding tiles are usually a warning sign that water is getting past the grout and sitting on or behind the tile adhesive. The diagnostic steps:

Stop using the shower if water can escape behind the loose tiles.
Tap-test the surrounding tiles. Hollow tiles indicate adhesive failure; investigate further.
Engage a licensed waterproofer or tiler. The likely findings are efflorescence (water under tiles), tile adhesive degradation, or membrane failure.
If the building is young enough to be under statutory warranty, lodge a defect complaint with Building Commission NSW or the QBCC as relevant, and notify the owners corporation so they can preserve any builder-warranty claim that runs to the building.
Document everything in writing. Photos of the falling tiles, the date the first one fell, the date you stopped using the shower, and the inspection report.

Loose tiles are rarely the end of the problem. They are the symptom that the system underneath has failed. A repair that only re-grouts or re-glues a few tiles is buying weeks, not years.

Statutory warranty: when the building is new

If the bathroom is in a recent build, there is usually a statutory warranty regime that runs alongside the body corporate's maintenance obligations. The clock starts the day the building is completed, not the day the leak appears, so prompt action matters.

NSW. Under section 18B of the Home Building Act 1989, statutory warranties run from completion. Section 18E sets the limitation periods: six years for a major defect, two years for any other defect. Waterproofing failure is generally a major defect because it threatens habitability and can damage major structural elements. The Design and Building Practitioners Act 2020 also applies a statutory duty of care to construction work on Class 2 buildings (extending to Class 3 and 9c buildings from 1 July 2025), and remedial waterproofing work on those buildings is regulated through Construction Issued Regulated Designs. The Building Commission NSW's Project Intervene program took compulsory action against developers for serious defects in Class 2 buildings within 10 years of OC; new building registrations for the program closed on 30 November 2023, but the underlying enforcement powers remain.

Victoria. The Domestic Building Contracts Act 1995 implies warranties that run for 10 years from the issue of the occupancy permit or certificate of final inspection. Victoria does not split the period between structural and non-structural. Waterproofing defects sit within the 10-year regime.

Queensland. The QBCC Home Warranty Scheme covers residential work over 3,300 dollars. Structural defects are covered for six years and six months from the contract date, extending to seven years where construction runs over six months. Non-structural defects are covered for 12 months. Owners must notify the QBCC within three months of becoming aware of a defect. Water penetration is treated as a structural defect for QBCC purposes.

WA. The Home Building Contracts Act 1991 and the Building Services (Complaint Resolution and Administration) Act 2011 set the framework. Statutory warranty periods follow the general six-year limitation common to most Australian jurisdictions, with structural matters often running longer.

SA. The Building Work Contractors Act 1995, section 32, implies statutory warranties for new residential building work, enforceable within the limitation periods set by general civil law.

Tasmania. The Residential Building Work Contracts and Dispute Resolution Act 2016 sets the framework, with implied warranties and limitation periods that follow the general approach.

ACT. The Building Act 2004 implies statutory warranties, with a six-year limitation under section 142.

NT. The Building Act 1993 sets the framework, with implied warranties and general civil limitation periods applying.

For a body corporate, the practical step on every waterproofing defect in a young building is to lodge a defect complaint with the relevant state regulator and preserve the warranty claim, even if the immediate repair is being managed under the body corporate's maintenance budget. The two pathways are not exclusive: the body corporate can repair now and recover from the builder later, provided the notice has been given in time. For more on the broader process, see the guide on forcing strata to fix a defect and the building defects after settlement post.

What insurance does and does not cover

Strata insurance is designed to cover sudden and accidental damage. The phrase carries weight.

A burst flexi hose in the bathroom, a tap that snaps off at the wall, a shower screen that shatters: these are sudden events. The insurer pays the resulting building damage. The lot owner's contents insurer pays the resulting damage to carpets, fittings and personal belongings.

A membrane that has been slowly leaking for six months, with efflorescence on the grout lines and a growing damp patch on the downstairs ceiling, is a gradual leak. Most strata policies exclude gradual seepage and wear and tear. The insurer can reduce or decline the claim.

The line between sudden and gradual is contested, and the Australian Financial Complaints Authority has decided multiple disputes in this area. AFCA's published approach treats "gradual" as occurring over months or years rather than days or weeks, and places the onus on the insurer to prove the exclusion applies. In one published determination (1006744), an insurer denied a claim on the basis of failed waterproofing and gradual deterioration; AFCA found the insurer had not produced evidence to prove gradual deterioration versus a sudden event, and required the claim to be paid. In a separate QBE matter, AFCA reached a similar result on a shower-area leak. There are also published decisions where claimants were caught by leak exclusions when the evidence supported a gradual cause.

For the owners corporation, the practical takeaway is that insurance is not a substitute for maintenance. A scheme with a documented bathroom inspection program, a record of membrane ages, and timely repairs gets a different reception from its insurer and from AFCA than a scheme that ignored the warning signs for two years. The water leaks from above post covers the cross-lot scenario in more depth.

For the lot owner, contents insurance is the policy that pays for damaged carpets, fittings and personal belongings. Strata pays for the building structure. The contents vs strata insurance post sets out what each policy covers when a wet area fails.

What a bathroom re-waterproofing actually costs

Indicative metro prices for 2025 and 2026:

Stand-alone re-waterproofing of a 6 to 8 square metre bathroom, in good substrate, on a ground-floor or low-level apartment: roughly 800 to 1,800 dollars including GST.
High-rise or restricted-access apartments: typically 10 to 20 per cent on top, due to access constraints, lift bookings and contractor downtime.
Strip-out, screed, re-membrane and re-tile without changing fixtures: roughly 8,000 to 15,000 dollars in metro markets.
Full bathroom renovation with new fixtures, where the membrane is part of the scope: typically 18,000 to 35,000 dollars or more depending on finishes, with waterproofing itself making up around 3 to 6 per cent of the total project cost.

The waterproofing is the cheapest line in the project. Doing it correctly the first time, with a licensed installer, certification at completion, and proper documentation, is dramatically cheaper than doing it twice.

Documentation a committee should hold

Whether the membrane sits on the lot or common property side of the line, the building benefits from holding the records.

The age of the original waterproofing in each wet area, taken from the developer's handover pack or estimated from the building's construction year.
Records of any subsequent re-waterproofing, including the contractor's licence, the product used, and the compliance certificate issued at completion.
For Queensland work post-1 September 2021, the relevant Form 43 Aspect Certificate from the QBCC licensee. (Form 16 is no longer issued for waterproofing in Queensland; the wet-area certification now sits in Form 43.) For NSW work in regulated buildings, the Regulated Design under the DBP Act and any compliance declaration at completion.
The history of any leaks, inspections and repairs by lot, including the original report, the scope of repair, and the post-repair certification.
Records of approved bathroom renovations, with any common property rights by-law transferring maintenance to the renovating owner.

Committee members rotate, managers change, owners sell. The building keeps the record. When the new owner of the apartment below asks why the ceiling is stained, the committee should be able to pull up the history of the bathroom above in minutes, not weeks.

A practical maintenance program

The committees that keep waterproofing claims down all do roughly the same things.

A wet-area inspection cycle. Every five years, a licensed waterproofer or building consultant walks the building's high-risk wet areas (top-floor bathrooms, bathrooms above habitable spaces, balconies over occupied units) and reports back on silicone, grout, tile condition, efflorescence, and visible signs of membrane failure. The report goes into the building's records.

A silicone replacement program. Silicone perishes faster than the membrane underneath. A scheme that replaces silicone at wall–floor junctions every five to seven years buys time on the membrane behind it. The cost is small; the protection is real.

Owner education at AGMs. Most bathroom failures show warning signs that owners ignore: perished silicone, hollow tiles, white efflorescence on grout lines, slow staining on the ceiling below. A two-page guide attached to the AGM notice, explaining what to look for and who to tell, lifts the quality of early reporting substantially.

Pre-renovation approvals run through to completion. Where an owner is approved to renovate a bathroom, the approval should include conditions on the waterproofing scope, the installer's licence, the compliance certificate at completion, and a common property rights by-law transferring future maintenance. Approvals that stop at "yes, you can renovate" are the ones that produce disputes five years later.

Insurance renewal review. The annual insurance renewal is the natural moment to look at the building's claims history and ask the broker whether there are interventions (silicone, balcony re-membrane, shower inspections) that would change next year's premium. Most brokers will engage with the question if the committee asks it.

How UnitBuddy fits

UnitBuddy gives committees and managers a shared place to record the building's wet-area history. The original construction certificates, the inspection cycle, the silicone replacement records, the renovation approvals, the common property rights by-laws, and the leak history by lot all sit in the same place.

The point of holding it together is the next leak. When the downstairs ceiling shows a stain, the committee should be able to pull up the lot above, see the age of the bathroom, the last inspection, the silicone replacement date, any prior repairs, and whether the renovation history makes the membrane lot or common property. That answer changes how the next conversation goes: with the lot owner, with the insurer, with the warranty regulator, and with the contractor doing the repair.

The component that fails is a thin sheet of rubber or polyurethane under the tiles. The system that prevents the failure cascade is documented maintenance and clear records of who is responsible for what. The latter is what UnitBuddy is built to support.

Sources and further reading

Further UnitBuddy reading: Water Leaks From Above: Who Pays in Strata?, Flexi Hoses: The $80,000 Apartment Claim, Building Defects After Settlement, How to Force Strata to Fix a Defect, Contents vs Strata Insurance, Changing Floor Coverings in Strata: A State-by-State Guide.

Bathroom Waterproofing in Strata: Leaks, Falling Tiles and the State-by-State Rules for 2026