Wet area showers in renovations
- Hamish Wakefield
- Jul 28
- 7 min read
Building consent, or no building consent?
Important note This article provides general information and reflects HWA’s interpretation of the legislation and guidance available at the date of publication. Building consent requirements depend on the building, the complete scope of work and the circumstances of each project. Determinations are specific to the cases they consider and should not be treated as universally binding precedents. Before undertaking building work, seek project-specific advice from an appropriately qualified professional or the relevant building consent authority.
I frequently come across Architects, Designers, Builders and Homeowners that rely on guidance documents rather than the actual legislation before making decisions or offering opinions.
Wet area showers are a classic case where many generally work on the assumption that installing a tiled or wet area shower in an existing home requires a building consent.
This is particularly relevant in alterations where a wet area shower or bathroom upgrade is required.
The reasoning for needing a building consent sounds sensible. A tiled shower relies on a waterproof membrane concealed behind the tiles. If that membrane is poorly installed, the resulting leak will cause significant damage before anyone knows there is a problem.
However, the question is not whether a tiled shower is important or potentially risky. The question is whether the Building Act actually requires a building consent for the work.
An MBIE determination I came across recently during a First Steps Engagement with a potential client looking to renovate their bathroom was very useful clarifying the wording within the Building Act and the guidance previously published to explain it.
What Schedule 1 actually says
Schedule 1 of the Building Act 2004 identifies building work that can be completed without obtaining a building consent.
Two exemptions are particularly relevant when renovating a bathroom in an existing dwelling.
Exemption 12: internal linings and finishes
Clause 12 exempts:
“Building work in connection with any internal linings or finishes of any wall, ceiling, or floor of an existing dwelling.”
The wording is notably broad. It does not exclude bathrooms, tiled showers, waterproof membranes or work considered particularly important.
Exemption 35: alterations to existing sanitary plumbing
Clause 35 allows existing sanitary plumbing to be altered without a building consent where:
the total number of sanitary fixtures in the building is not increased
the alteration does not modify or affect a specified system
the plumbing is undertaken by an authorised person.
This means an existing shower, bath, basin or toilet can generally be replaced or repositioned without a building consent, provided the total number of sanitary fixtures is not increased and the other conditions of the exemption are met.
MBIE’s current guidance gives the example of a homeowner repositioning or replacing a shower within an existing bathroom as exempt work. It also says that a bath with a shower over it is treated as two fixtures, allowing it to be replaced with a separate bath and proprietary shower without consent.
So where did the belief that tiled showers always require consent come from?
The guidance did not match the Act
Earlier editions of MBIE’s Building work that does not require a building consent guidance stated that installing a tiled wet area shower in an existing dwelling required a building consent.
The guidance described waterproof membranes as “critical building work” and said they therefore sat outside the exemptions.
That position has become widely accepted. It was repeated by councils and industry professionals and became, for practical purposes, the default rule.
The problem was that the expression “critical building work” did not appear in the relevant Schedule 1 exemption.
Clause 12 did not carve waterproof membranes out of its broad exemption for internal linings and finishes.
This discrepancy was examined directly in Determination 2024/054.
What Determination 2024/054 found
The determination concerned two tiled showers installed in an existing dwelling.
One replaced an existing shower and another replaced an existing bath. The new showers had acrylic shower floors and tiled walls installed over waterproof membranes.
The work was not included within a building consent.
The showers subsequently leaked. Cracking in the tiled finishes allowed water to penetrate behind the linings and into concealed spaces, causing damage to the floor and framing.
The subsequent new owners of the house argued that the work should have required a building consent. In support of that position, they referred to MBIE’s own guidance, which stated that installing waterproof membranes beneath tiled shower walls was critical building work requiring consent.
MBIE’s determination however has reached a different conclusion.
It found that the shower-wall construction comprised:
the backing substrate attached to the framing
the wet area membrane
the tiles
the associated fixings, adhesives and grout.
Together, these elements were considered internal linings and finishes. Because the work was undertaken in an existing dwelling, it fell within clause 12 of Schedule 1.
The determination stated:
“The guidance does not supersede the Act or its regulations. Clause 12 of Schedule 1 does not exclude wet area membranes as internal linings covered under that exemption.”
It concluded that a building consent had not been required for the installation of the wet area membrane as part of the two tiled showers.
That is a fairly unequivocal rejection of the position contained in MBIE’s earlier guidance.
Exempt does not mean optional compliance
There is an important second half to the determination.
Although the work did not require a building consent, the showers still had to comply with the Building Code.
They did not.
The determination found that the showers failed to comply with clauses E3.3.4, E3.3.5 and E3.3.6 of the Building Code. The surfaces were not sufficiently impervious and had not prevented water from penetrating behind the linings and into concealed spaces.
This distinction is fundamental:
Not requiring a building consent does not mean the Building Code does not apply.
All building work must comply with the Building Code, whether or not it is consented. The difference is that exempt work is not submitted to the council for approval and is not ordinarily inspected by the council during construction.
The responsibility for choosing an appropriate system, using competent tradespeople and retaining evidence of compliance therefore rests more directly with the owner and the people carrying out the work.
Does this mean every wet area shower is consent-free?
No. The determination should not be stretched further than its facts or the wording of Schedule 1 allows.
A building consent will still be required where the wider bathroom work includes:
adding sanitary fixtures rather than replacing or relocating existing ones
altering load-bearing walls or structural framing
modifying bracing elements
making significant structural changes to form a recessed or level-entry shower
affecting a fire separation or another specified system
altering drainage beyond the applicable exemptions
work in a building that is not an existing dwelling
work that falls outside the conditions of the relevant Schedule 1 exemptions.
Determination 2024/054 involved acrylic shower floors installed on the existing floor structure, with waterproofed and tiled walls. It did not specifically decide every possible fully tiled, level-entry or structurally recessed shower arrangement. However provided there is no structural change required the act refers to floor, wall and ceiling.
Each component of the proposed work needs to be considered separately. The plumbing may be exempt under clause 35 and the linings and membrane under clause 12, while structural or fire-related work within the same renovation may still require consent.
MBIE’s guidance has now changed
Interestingly, MBIE’s current guidance no longer lists a tiled wet area shower as an example of work that requires consent under exemption 12.
Instead, it says the exemption allows any or all of the linings and finishes to walls, ceilings or floors of an existing dwelling to be replaced or altered.
It recommends obtaining suitably qualified advice where the work could affect structural performance, fire safety or internal moisture compliance.
That is much closer to the wording of the Act and the conclusion reached in Determination 2024/054.
However, the old position has been repeated for so long that the belief that “tiled shower equals building consent” remains deeply embedded across the industry.
The practical approach
If you are replacing or repositioning an existing shower in an existing home, a tiled finish and waterproof membrane do not, by themselves, necessarily trigger the need for a building consent.
Before proceeding, the entire scope should still be checked against Schedule 1. Any plumbing must be completed by an authorised plumber, and the work must comply fully with the Building Code.
For a tiled or wet area shower, I would also recommend retaining clear records, including:
plans or sketches showing the completed arrangement
the waterproofing system specification
evidence that the system is suitable for the particular substrate and shower construction
the installer’s qualifications or product approval
photographs of the substrate, junctions and completed membrane before tiling
producer statements, warranties and installation records
plumbing documentation.
Owners can also provide records of exempt work to their council for inclusion on the property file. This does not amount to council approval or produce a Code Compliance Certificate, but it can help explain the work to a future purchaser.
The wider lesson
Firstly don't rely on guidance documents alone. They are frequently misleading. Go to the source of the information and spend the time reading the text. There are still anomalies but at least you have a source closer to the truth.
Secondly Determination 2024/054 is not an argument for lowering the standard of bathroom construction. If anything, the failed showers show why wet area waterproofing must be taken seriously.
What it does demonstrate is the importance of separating three different questions:
Does the work require a building consent?
Does the work comply with the Building Code?
Has the owner retained enough evidence to demonstrate that compliance later?
Those questions are related, but they are not the same.
For years, simplified guidance effectively turned a prudent industry practice into something presented as a legal requirement. The determination confirms that guidance cannot add restrictions that are not found in the Act itself.
A tiled shower may be high-risk work. It may deserve careful design, competent installation and good documentation.
But in an existing dwelling, it does not automatically require a building consent simply because it contains a waterproof membrane.
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