Bathroom Renovations in Townhouses and Duplexes: What’s Different, What to Confirm Before You Start
Shared walls. Strata approvals. Access constraints. Three things a standalone house renovation doesn’t have — and three things that determine whether a townhouse or duplex bathroom renovation goes smoothly or doesn’t.
The renovation work itself is largely the same. Same compliance requirements under AS 3740, same licensed trades, same materials and wet area specifications. What’s different is the context it happens in — and what has to be resolved before a tradie sets foot on site. Scope that looks simple in a standalone house can be significantly more involved when a party wall is involved, or when an owners corporation has a say in what gets approved.
Here’s what to understand before you lock in scope.
What’s Different About Renovating a Bathroom in a Townhouse or Duplex
Most of the renovation work is identical to any bathroom. The compliance requirements are the same, the trades are the same, and the materials specification doesn’t change because the title document says ‘strata’. What changes is the context — and several constraints that don’t appear on a floor plan but do appear in the final bill when they’re not accounted for upfront.
Shared party walls
An attached townhouse or duplex shares at least one wall with the adjoining dwelling. When that wall is in a bathroom, waterproofing it correctly matters for both properties. The liability if water egress causes damage to the neighbouring unit sits with whoever owns the renovation work — not the building’s original builder, not the strata manager. Getting the membrane right on a shared wall is not optional.
Strata approval obligations
Strata-titled townhouses sit within an owners corporation scheme with by-laws that govern what owners can and can’t do to their lot. Work that is structural, modifies common property, or alters waterproofing may require a by-law approval or special resolution before any trade can start. The timeline for that approval is outside the owner’s control — and outside the contractor’s. Booking trades before approval is granted is a common and expensive mistake.
Access constraints
Townhouses regularly have no side access, narrow internal corridors, shared driveways, and restricted staging areas. Waste removal and material delivery take longer — and cost more — than on an open suburban block. Quotes that don’t account for site-specific access tend to produce variations once work is underway.
Multi-storey wet area configurations
A three-storey townhouse with bathrooms on multiple floors means wet areas in close vertical proximity. A waterproofing failure on an upper-floor bathroom doesn’t stay on that floor. Scope discussions for a renovation that only touches one bathroom are sometimes incomplete when the floor structure beneath it hasn’t been assessed.
Neighbour notification
Even where strata approval is not formally required, work that affects a shared wall or generates sustained noise typically carries neighbour notification expectations. In a strata scheme, some by-laws make this mandatory. Confirming with the strata manager before work starts costs nothing. Disputes after the fact cost considerably more.
Related: The planning steps that matter before scope is locked in are covered in our renovation planning guide. See our bathroom renovation planning guide ›
Strata Renovations: What Requires Approval and What Doesn’t
Not every bathroom renovation in a strata property needs owners corporation sign-off. The trigger is whether the work is cosmetic or structural — but ‘structural’ under a strata by-law is interpreted more broadly than it is in building code terms, and the line between the two is in the by-laws, not in common sense.
The table below gives a general guide. It is not a substitute for reading the by-laws of the specific scheme.
By-laws vary between strata schemes. What one scheme classifies as cosmetic, another may require a special resolution on — particularly for waterproofing work, which several schemes treat as a common property matter regardless of which side of the lot boundary the membrane sits on.
The strata manager or owners corporation secretary is the correct authority on what requires approval in a specific scheme. Get the answer in writing. Allow for the approval timeline in the renovation schedule — typically four to eight weeks, but occasionally longer in schemes with infrequent meetings or contested resolutions.
Related: Renovation sequencing — including how to build approval timelines into a realistic project schedule — is covered in our renovation process guide. See our bathroom renovation process guide ›
Shared Walls and Waterproofing: The Liability Issue Nobody Mentions at the Quote Stage
Water damage that starts in one dwelling and reaches the adjoining one is a dispute. In a duplex or attached townhouse, a bathroom on the party wall is the most common origin point — and the most common cause is waterproofing that wasn’t done correctly the first time, or wasn’t done at all.
AS 3740 applies to every residential bathroom wet area regardless of property type. A duplex bathroom is not a different category of wet area with different standards. The membrane requirements, substrate requirements, and licensed trade requirements are identical to those in a freestanding house.
A licensed waterproofer is legally required under the Home Building Act for wet area waterproofing in NSW. The licence is verifiable through the Service NSW contractor licence check. Waterproofing work in a shared-wall bathroom by an unlicensed operator is both a compliance failure and a liability exposure that extends to the adjoining property owner.
The shared wall itself needs membrane coverage to the full extent specified by AS 3740 for the location — not just the visible surface, but including substrate preparation and all penetrations. A membrane that stops short of a pipe penetration, or that’s applied over a surface that wasn’t correctly prepared, will fail. The question is when.
If existing tiles are being replaced like-for-like and the substrate and membrane are not being disturbed, the membrane may not need to be touched. If the substrate is being replaced — and on most renovation jobs in older properties, it should be assessed rather than assumed intact — the membrane is replaced with it.
Important: Waterproofing on a shared wall is not purely a compliance question — it is a civil liability question. If water egress from a renovation causes damage to the adjoining property, the liability attaches to the renovation owner and the trades who performed the work. A licensed waterproofer, a correctly applied membrane, and a compliant installation are the protection. A cheap quote that doesn’t itemise waterproofing separately is worth examining carefully before signing.
Related: Full compliance requirements for wet area waterproofing under AS 3740 are set out in our waterproofing compliance guide. See our AS 3740 waterproofing compliance guide ›
What Matters Most — By Property Scenario
The dominant renovation consideration shifts depending on the ownership structure and configuration of the property. The same bathroom renovation carries different priorities depending on which of these four scenarios applies.
Strata approval is the critical path item. Nothing structural should be quoted or contracted until approval is confirmed in writing. Build the approval timeline into the schedule before booking any trades — four to eight weeks is typical, and approvals are not granted because a tiler has a gap in their schedule.
No strata approval process to manage, but shared-wall waterproofing liability applies in full. The cost of a correctly licenced, correctly applied waterproofing membrane is small relative to the cost of a water ingress dispute with the occupant of the adjoining lot.
Full control over scope and timing. Shared-wall obligations still apply regardless of title structure. The adjoining occupant is a neighbour — notification before noisy or disruptive work is practical and, in most circumstances, expected.
Multiple wet areas in the same build means a waterproofing schedule, not just individual bathrooms. Sequence matters: upper floors before lower, wet area inspections at each membrane stage, sign-off documented before the next trade proceeds.
What a Bathroom Renovation Costs in a Townhouse or Duplex
The cost of a bathroom renovation in a townhouse or duplex is not categorically higher than in a standalone house — but several factors regularly push it above the equivalent freestanding-property figure. Access constraints add labour time. Strata approval processes add fees and dead time between planning and mobilisation. Shared-wall waterproofing requirements add a compliance layer that can’t be skipped.
The ranges below are indicative. They are not quotes. Scope, site conditions, existing substrate condition, and finish specification all move these numbers. The purpose of these figures is context, not budgeting.
A quote significantly below the lower end of these ranges for the scope described is either missing line items or pricing them in a way worth clarifying before signing. Substrate preparation, licensed waterproofing, and access allowances are the items most commonly omitted from low quotes — and the most commonly required on real jobs.
Related: See our full bathroom renovation cost guide for a complete breakdown by scope and specification. See our bathroom renovation cost guide ›
Have questions about renovation scope in a townhouse or duplex? We connect homeowners and investors with experienced, vetted renovation specialists across NSW and ACT. Lifestyle Bathrooms is a referral and connector service — not a licenced contractor. Request a free consultation ›
Before You Start: Nine Things to Confirm for a Townhouse or Duplex Bathroom Renovation
These are the questions most commonly skipped at the planning stage — and the ones that produce the most avoidable delays and cost overruns when they are.
Strata approval status confirmed
Is the scope cosmetic or structural under the relevant by-laws? If structural, has approval been granted in writing before trades are booked?
By-laws reviewed
A copy of the current by-laws has been obtained and the relevant clauses checked — not assumed to be standard.
Owners corporation notified
Even where formal approval is not required, notification of planned works is expected and often required under the by-laws.
Licensed waterproofer engaged
Waterproofing in a wet area requires a licensed contractor under the Home Building Act. Licence confirmed before contract is signed.
Shared-wall implications assessed
If the bathroom adjoins a party wall, waterproofing scope and existing substrate condition have been assessed by the waterproofer before quoting — not after mobilisation.
Scope documented before quoting
Full scope including substrate work, membrane replacement, and any plumbing relocation is in writing. Verbal scope produces variations.
Substrate prep itemised in quotes
Levelling compound, fibre cement sheet type, and application method are specified line items, not implied inclusions.
Site access assessed
Delivery route and waste removal path have been walked. Access costs are in the quote before work starts, not flagged as a variation afterwards.
Neighbour notification planned
Where work is noisy, disruptive, or affects a shared wall, the adjoining occupant has been informed before work begins.
Common Questions
Depends on scope. Like-for-like cosmetic work — tile replacement on existing substrate, fixture swap with no plumbing relocation, regrouting — typically doesn’t require owners corporation approval. Any work that is structural, alters the waterproofing membrane, affects common property, or relocates plumbing usually does.
The boundary isn’t always intuitive. Replacing a waterproofing membrane is treated as structural under many by-laws, even if no walls are touched. A complete shower strip-back and rebuild on an existing footprint would trigger approval in most schemes.
The answer is in the by-laws of the specific scheme — not in general guidance. Get a copy, check the relevant clauses, and confirm with the strata manager before scope is finalised. Building the approval process into your project timeline before trades are booked is cheaper than having to pause a renovation mid-way through.
The owners corporation can require you to reverse the work at your own cost. That means removing the renovation, reinstating the original condition, and paying for the remediation work — plus any damage caused to common property.
In schemes with stricter by-laws, unapproved structural work can also create a liability if it later causes damage to an adjoining lot or common property. The risk isn’t hypothetical: owners corporations do pursue these outcomes when disputes arise.
Yes. AS 3740 defines the wet areas that require waterproofing in residential buildings — shower recesses, bath surrounds, floors, and adjacent walls within specified distances — and those requirements apply regardless of whether the property is a house, apartment, or duplex. A duplex is not a different category. Licensed waterproofer, correct membrane, correct substrate: the standard is the same.
Yes, if the site supports parallel trades and occupancy allows it. If the property is tenanted, both bathrooms out of service simultaneously is rarely viable — one at a time is the practical approach.
If the property is vacant during the renovation, sequencing both bathrooms within a single mobilisation period is usually more cost-efficient: trades are already on site, scaffolding and access are already in place, and the combined scope often attracts better pricing than two separate jobs. Worth discussing with whoever is quoting the work.
Access constraints are the main driver. Narrow corridors, no side access, shared driveways, and restricted staging areas mean materials take longer to bring in and waste takes longer to remove. Labour time goes up accordingly.
Strata approval adds fees and a scheduling gap — trades can’t be booked until approval is granted, and that gap has a cost if it delays a renovation into a different availability window. For shared-wall wet areas in duplexes, a correctly licenced and correctly applied waterproofing membrane adds cost that a standalone house renovation on an interior wall doesn’t carry. The work itself isn’t more expensive. The conditions are.