How to Renovate a Bathroom: Order of Trades, Compliance Requirements, and What Goes Wrong When the Process Gets Skipped
A bathroom renovation is a sequenced build process, not a series of independent decisions. The order in which trades work — and whether each stage is completed correctly before the next begins — determines whether the finished renovation holds or fails behind walls you can no longer see.
Most renovation failures visible after completion were locked in before work started or in the wrong sequence. Waterproofing applied over an inadequate substrate. Tiling started before membrane cure time was observed. Fit-off completed before movement joints were sealed. The repair cost for each is a multiple of what correct process would have cost.
This guide covers the complete renovation process: the correct order of trades, what compliance requirements apply at each stage, what documentation should exist at completion, and what goes wrong when any of it is skipped.
Why the Order of Work Determines Whether the Renovation Holds
Bathroom renovation is not a set of parallel tasks you can run in any order for convenience. It is a sequenced build process where each stage creates the conditions the next stage depends on. That sequencing isn’t a preference — in many cases it is a compliance requirement under Australian Standards and the NCC.
The practical consequences of getting the sequence wrong are consistent: waterproofing applied before the substrate was adequately prepared; tiling started before the membrane had reached its required cure time; movement joints filled with grout because the silicone was an afterthought; plumbing fit-off completed before the tile cutouts were planned. None of these failures are immediately visible.
That invisibility is the problem. Most bathroom renovation failures surface 12 to 36 months after completion — long enough after handover that the contractor is gone, warranty claims are complicated, and the repair scope has grown. The damage was there on day one. It just took time to become visible.
The most effective risk mitigation in a bathroom renovation is understanding what the correct sequence is, what each stage requires of the stage before it, and what the consequences are when the process is compressed or skipped. That’s what this guide covers.
Related: The shortcuts that most commonly compromise the renovation sequence are documented. See renovator red flags ›
The Correct Order of Trades in a Bathroom Renovation
The sequence below covers the correct order for a full bathroom renovation — demolition through to finishing. Variations exist for partial works or cosmetic updates. In a full renovation, any deviation from this sequence should be understood and agreed in writing before work starts, not discovered when a problem emerges later.
Strip fixtures, tiles, and substrate. The stage where hidden problems surface: rot behind walls, failed previous waterproofing, substrate damage. Document everything before it’s covered. What’s found here determines substrate scope and cost for everything that follows.
Relocate or extend waste and supply lines to match the new layout. Must be completed before substrate is installed. Any change to shower, toilet, or basin position happens here. Licensed plumber required in NSW and ACT.
Install or extend conduit, exhaust fan wiring, and lighting circuits before boarding. If the layout includes underfloor heating or a heated towel rail, conduit goes in now. Licensed electrician required. Must be completed before substrate installation.
Compressed fibre cement sheet installed to walls and floor in wet zones. Must be flat to the tolerance required by the tile format — large-format tiles require 3mm over 3 metres. Most existing substrates need levelling compound to meet this. Not the stage to cut cost.
Membrane applied to floor and wet area walls under AS 3740. Licensed waterproofer or builder required. Full cure time must be observed — typically 24–48 hours minimum per manufacturer specification. The stage most commonly rushed under schedule pressure.
In NSW, waterproofing in a Class 1 or 10 building is a mandatory inspection point before it is covered. The tiler should not start until this inspection has occurred and been documented. If your contract doesn’t name this as a hold point, raise it before work starts.
Tile type, slip ratings (AS 4586), and adhesive specification must be confirmed before this stage begins. Back-buttering required for large-format tiles. Movement joints at all internal corners and changes of plane. Grout selection confirmed in writing before work starts.
Tapware, shower fittings, toilet suite, vanity, and basin installed after tiles are set and cured. Tile cutouts for fixtures must be planned before tiling, not improvised after. Licensed plumber completes this stage.
Lighting, exhaust fan, and heated towel rail connections completed after tiling and fit-off plumbing. Must be completed by a licensed electrician. Electrical safety certificate issued at completion.
Silicone sealant at all movement joints and the bath-to-wall junction. Grout applied and sealed. Natural stone sealed if specified. Defect inspection completed. This stage is where shortcuts taken earlier in the build become visible.
Related: Waterproofing compliance under AS 3740 is covered in full in our dedicated guide. See the AS 3740 waterproofing guide ›
What Requires a Licensed Tradesperson — and Why It Matters If You Skip It
Three categories of work in a bathroom renovation require a licensed tradesperson in NSW and ACT: plumbing, electrical, and waterproofing in wet areas. These are legal requirements under the Home Building Act 1989 (NSW) and equivalent ACT legislation — not optional specifications left to contractor discretion.
Plumbing work — connecting or disconnecting from the waste or supply system, relocating drainage, installing fixtures that connect to water supply — must be performed by a licensed plumber and drainer. In NSW, plumbers must hold a current licence issued by Service NSW. Work not signed off by a licensed plumber is unlicensed construction work regardless of who performed it.
Electrical work must be performed by a licensed electrician. The scope in a bathroom renovation typically includes lighting, exhaust fan wiring, underfloor heating where specified, and heated towel rail connections. Unlicensed electrical work in a wet area carries both a compliance risk and a direct safety risk that unlicensed work in dry areas of the house doesn’t carry.
Waterproofing is the least understood licensing requirement. In NSW, waterproofing in a wet area of a Class 1 residential dwelling must be performed by a licensed builder or licensed waterproofer. An unlicensed contractor applying membrane — regardless of the product used or apparent quality — is performing unlicensed construction. Waterproofing failures are invisible until they’ve caused structural damage. They can take years to surface, by which point undocumented unlicensed work creates a problem extending well beyond the bathroom.
Related: Unlicensed renovation work creates compliance, insurance, and resale obligations. See our NCC bathroom standards guide ›
Waterproofing Compliance Under AS 3740 — What the Standard Actually Requires
AS 3740 is the Australian Standard for Waterproofing of Domestic Wet Areas. It specifies where waterproofing membranes must be applied, how far up walls they must extend, what products and methods are acceptable, and what cure times must be observed before the membrane is covered. It applies to every residential bathroom renovation in Australia and is referenced in the National Construction Code.
In practice, AS 3740 defines four key requirements: the wet area zones that must be waterproofed; the minimum membrane height on walls in each zone; the treatment of all penetrations through the membrane; and the requirement that the membrane be given its specified cure time before it is tiled over. Each of these has a specific failure mode when it isn’t met.
The table below maps each wet area zone to its compliance requirements under AS 3740. These are minimums. Contractors working above them are not in breach. Contractors working below them are.
One requirement skipped on time-pressured jobs more than any other: cure time. Membrane products have specified minimum cure times before they can be covered — typically 24 to 48 hours depending on product and ambient conditions. Tiling over an uncured membrane produces no immediate failure. The failure comes later, and the repair requires full strip-out.
Related: AS 3740 requirements are explained in full in our waterproofing compliance guide. See AS 3740 waterproofing guide ›
Not sure if your renovation brief covers all of this? We connect homeowners and property professionals in NSW and ACT with vetted bathroom renovation specialists who can review your scope before work starts. Lifestyle Bathrooms is a referral and connector service — not a licenced contractor. Request a free consultation ›
Inspections, Sign-Off, and the Documentation That Should Exist at Completion
In NSW, waterproofing in a Class 1 or Class 10a building is a mandatory inspection point before the membrane is covered. The membrane must be applied, inspected, and documented before tiling begins. On renovation works under a building consent or CDC approval, the inspection requirement and who performs it depends on the contract structure — confirm this arrangement before work starts, not when the waterproofer is packing up.
The tiler should not lay a single tile until the waterproofing has been inspected and the inspector is satisfied the membrane meets AS 3740 — correct zone coverage, correct height on walls, penetrations sealed, and cure time observed. A tiler who starts work without sight of a waterproofing sign-off is taking on risk that belongs to the waterproofer.
At practical completion, a correctly documented bathroom renovation should include: a waterproofing certificate of completion; a plumbing compliance certificate (Form 6 in NSW, issued by the licensed plumber); and an electrical safety certificate (issued by the licensed electrician). If the renovation required development consent or a CDC, the relevant certifier documentation should also be in hand.
If a contractor cannot produce these documents at completion, request them before releasing final payment. Documentation is the only evidence of licensed trade compliance that exists once the walls are tiled. Without it, a future purchaser, insurer, or certifier has no basis to verify the renovation was built correctly.
Related: NCC inspection obligations and building compliance requirements are explained in our standards guide. See our NCC bathroom standards guide ›
What a Bathroom Renovation Costs in NSW and ACT — by Trade and Phase
Tiling labour is the most visible cost in a bathroom renovation quote but not the largest variable. Substrate preparation — which varies significantly based on what’s found under existing tiles — is the most frequently underpriced and underscoped item. Waterproofing, plumbing, and electrical costs are relatively consistent, but only when they’re quoted as separate line items rather than absorbed into a single lump sum that obscures what has actually been allowed for.
The ranges below are indicative for NSW and ACT. Scope, access, site conditions, and fixture specification move these numbers significantly. A quote meaningfully below the lower end of the range for a given trade or phase warrants clarification on what has been omitted before you sign.
Not Sure What Your Renovation Scope Should Include?
Tell us about the bathroom and the work you’re planning. 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.
Renovation Failures That Show Up Later — and Cost More to Fix Than to Prevent
The common thread in most bathroom renovation failures: the conditions that caused them were present from day one. They didn’t surface until later — usually later enough that the repair bill is a multiple of what correct original installation would have cost.
Waterproofing membrane failure behind tiles
A failed waterproofing membrane is the most expensive bathroom renovation failure. The membrane was applied incorrectly, cured too quickly under schedule pressure, or was cut short of the height required under AS 3740. Water migrates behind the tile field slowly, saturating the substrate and structural framing. By the time it appears as a damp wall, peeling paint, or mould on an adjacent surface, the damage is typically 3–5 times the cost of waterproofing done correctly. The only fix is full strip-out. A waterproofing inspection before tiling creates accountability that completely undocumented work doesn’t.
Substrate failure and tile debonding
A tile that comes off the wall or lifts at a floor edge didn’t fail because the tile was defective. The adhesive and substrate failed. This occurs when the board type was inadequate for the location, the substrate wasn’t flat to the tolerance required by the tile format, or back-buttering was skipped. Large-format tiles require substrate flatness of 3mm over 3 metres. Most existing substrates need levelling compound to meet this. Addressed in the quote, it costs $20–$55 per m². Addressed after tile failure, the cost is significantly more.
Grout cracking at movement joints
Grout is rigid. Internal corners, floor-to-wall junctions, and the bath-to-wall line are movement joints that accommodate fractional movement from temperature cycling and building load. Rigid grout in a flexible joint cracks. Water finds the gap. The damage builds behind the tile field until it becomes externally visible — by which point the waterproofing membrane beneath may have been compromised. The correct material in movement joints is flexible silicone sealant. This is a requirement under AS 3740 and the NCC, not a stylistic preference.
Non-compliant trade work discovered on resale
Bathroom renovations that included unlicensed plumbing, electrical, or waterproofing create a mandatory disclosure obligation in NSW on resale. In practice, this surfaces during building inspections or when a buyer’s solicitor requests evidence of licensed trade work. Options at that point are: rectification (typically requiring tile removal), price adjustment, or an abandoned transaction. None of these outcomes was cheaper than licensed work at the time of renovation. Unlicensed work also creates insurance implications — a home insurance claim from a bathroom failure may be declined if the relevant work was performed without a licence.
Non-compliant slip rating on shower floor tiles
A shower floor installed with tiles that don’t meet the P4 rating required under AS 4586 is a compliance failure with insurance and liability implications. It’s invisible after installation — you cannot identify a non-compliant tile by looking at the finished floor. The only point of prevention is the product data sheet, confirmed before the tile is ordered. After installation, options are surface grinding — which changes the finish and may void the tile warranty — or full removal and replacement. Neither is expensive to avoid if the question is asked at the right stage.
Related: See the full list of renovation shortcuts and warning signs. See renovator red flags ›
Before Work Starts: What to Confirm Before Your Renovation Begins
Ten things worth confirming before work starts. Not a comprehensive specification — a checklist of the questions most commonly skipped, and that most consistently produce avoidable problems when they are.
All licensed trades confirmed and verifiable
Waterproofing, plumbing, and electrical contractors hold current licences. Verify through Service NSW before work begins — ask for licence numbers, not just verbal assurances.
Waterproofing specification written into the contract
Membrane type, zone coverage, and wall heights specified in the scope. If waterproofing appears only within a lump-sum tiling line, ask for it itemised separately before signing.
Pre-tile waterproofing inspection agreed as a hold point
Tiling cannot begin until the membrane has been inspected and documented. This should be a named hold point in the programme, not something confirmed informally on the day.
Substrate preparation separately itemised in the quote
Levelling compound, board type, and fixing method specified. This is the item most consistently absent from low quotes and most consistently required on existing substrates.
Tile slip ratings confirmed per location
P3 minimum for general bathroom floor, P4 for shower floor and bath surround. AS 4586 classification confirmed on the product data sheet before the tile is ordered.
Tile water absorption confirmed for wet zones
Impervious classification (below 0.5% absorption) for shower walls and floor. Confirm from the product data sheet, not from a description in the showroom.
Movement joints specified at all internal corners
Silicone sealant at every change of plane, internal corner, and bath-to-wall junction. If the scope document says grout at these locations, ask for a correction before signing.
Fixture lead times confirmed before demolition begins
Vanities, shower screens, and some tapware carry 4–8 week lead times. Starting demolition before fixtures are confirmed and on order creates avoidable holding periods mid-renovation.
Completion documentation listed as contractual deliverables
Waterproofing certificate, NSW Form 6 plumbing compliance certificate, and electrical safety certificate specified as required deliverables. If they’re not in the contract, add them before signing.
Adhesive type confirmed for tile format and location
Flexible adhesive for large-format tiles, heated floors, or any installation with expected substrate movement. Standard-set adhesive is not appropriate in these contexts.
Common Questions
A standard bathroom renovation takes 2–4 weeks of on-site work from demolition to practical completion, assuming no layout changes to waste lines, no substrate surprises during strip-out, and all trades coordinated in the correct sequence. Marketing timelines of “one week” apply to cosmetic-only renovations — no waterproofing, no substrate replacement, no fixture changes.
Allow 4–6 weeks from contract signing to practical completion as a realistic planning figure, including pre-start lead time for fixtures. The most common delay causes are: waterproofing cure time compressed under schedule pressure; fixture lead times not confirmed before demolition; and stages needing to be revisited because they weren’t completed correctly the first time.
In NSW, plumbing, electrical work, and waterproofing in wet areas all require licensed tradespersons. Plumbing work must be performed by a licensed plumber and drainer. Electrical work must be performed by a licensed electrician. Waterproofing of wet areas in a residential dwelling must be performed by a licensed builder or licensed waterproofer.
Performing any of these works without a licence — or engaging an unlicensed contractor — constitutes unlicensed construction work under the Home Building Act 1989. Consequences include insurance implications, mandatory disclosure obligations on resale, and potential liability if a subsequent failure or injury occurs. Verify licences through Service NSW before work commences.
AS 3740 is the Australian Standard for Waterproofing of Domestic Wet Areas. It specifies where waterproofing membranes must be applied, how far up walls they must extend, what products and methods are acceptable, and what minimum cure times apply before the membrane is covered. It applies to every residential bathroom renovation in Australia and is referenced in the National Construction Code.
If a renovation contractor hasn’t mentioned AS 3740 compliance, waterproofing certification, or a pre-tile inspection, raise it before work starts. The full requirements are covered in our AS 3740 waterproofing guide ›
Demolition — removing tiles, non-structural elements, and fixtures — can generally be done by a homeowner in NSW, subject to the scope not touching licensed trade services. Preparation work including site clearing and waste disposal is also typically within owner scope.
What cannot be done by an unlicensed person: plumbing work connecting to or from the waste or supply system; electrical work other than like-for-like fitting replacement under permitted work provisions; and waterproofing in a wet area. The cost saving is typically modest against the compliance, insurance, and resale risk created. A better approach is agreeing with your contractor which preparation stages can be owner-managed within the programme.
The items most consistently absent from low bathroom renovation quotes are: substrate preparation and levelling as a separate itemised line ($20–$55 per m² — routinely excluded from quotes on existing substrates); waterproofing as a separate line rather than absorbed into tiling labour; and distinct line items for each licensed trade rather than a single bundled figure.
A quote that bundles plumbing, electrical, and waterproofing into a single labour figure warrants questions about scope and licensing before you sign. Our guide to renovator red flags › covers the patterns in more detail.