Undersized and inaccessible risers are a growing compliance issue in Australia’s multi-residential sector, creating costly remediation and long-term maintenance challenges. Casey McGuire explores the topic further.

Australia’s multi-residential construction sector is facing a persistent problem: Undersized and inaccessible risers. Once treated as a minor design issue, these narrow shafts now trigger defect notices, costly remediation and long-term maintenance headaches for owners and strata managers.

Commercial pressures have steadily pushed apartment designs toward tighter footprints. Full-height accessible risers have been replaced by boxed-in shafts, leaving minimal room for compliant pipework, fire separation and future maintenance.

One of the most common problems under scrutiny is the continued use of undersized risers. When these spaces aren’t properly sized, they fall short of the intent and minimum requirements of both AS/NZS 3500 and NCC Volume One and good design intent. These standards detail essential factors such as accessibility for inspection, testing and maintenance, minimum clearances around pipework, fire-stopping and the fire-rated integrity of penetrations and the serviceability requirements needed to ensure plumbing systems remain maintainable for the full life of a building.

“The root problem is commercial pressure, particularly the developer’s desire to maximise net lettable area (NLA). Even a fractional spatial gain per apartment becomes financially attractive,” Hydraulic Solutions chief executive David Steblina says.

“For over a decade, the industry has largely self-regulated riser design. Architects and developers determined spatial allowances based on their own templates and consultants were routinely instructed to ‘make it work’. Full-height accessible risers, common in earlier construction eras, have been replaced with narrow, boxed-in shafts with minimal or no service access.”

Regulatory authorities, particularly in New South Wales, have become significantly more proactive over the past five years. They are now enforcing AS/NZS 3500 and National Construction Code (NCC) requirements with far greater rigour, issuing retrospective defect notices for issues such as inadequate access, non-compliant fire separation and insufficient clearances for installation or maintenance.

This shift has exposed long-standing design shortcomings and raised compliance expectations across the entire construction and plumbing sector.

When risers are narrowed below practical limits, contractors are often forced into compromised installation layouts. This can make it impossible to fit compliant fire collars on horizontal branches, create non-compliant separation between hot, cold, sanitary, gas and electrical services and eliminate safe access for inspecting or replacing failing components.

In practice, an undersized riser is far more than a minor design oversight. It can often become a structural defect that prevents compliance with multiple sections of the NCC and the AS/NZS 3500 suite, while creating long-term risks and maintenance challenges for building owners, designers and trades alike.

“Contractors are expected to install multiple vertical stacks, junctions, test risers and separation elements in shafts that are physically incapable of accommodating them. This results in improvised installation, fire-rating breaches and long-term maintenance hazards,” David says.

“These failures originate at the design stage but propagate right through to construction and certification, where they can result in non-conformances that are costly and complex to rectify.”

Well, who is actually responsible?

Responsibility for ensuring compliant riser design and installation is complex and spread across multiple parties, each playing a critical role in both the planning and execution stages of a building project.

Because the riser footprint is not part of the sellable NLA, the developer often drives spatial compression to maximise their NLA and commercial yield, putting pressure on the overall design. Architects, as lead designers, control apartment layouts and riser footprints, and their early decisions set the constraints that all other stakeholders must work within.

Hydraulic designers frequently inherit riser dimensions that have already been “locked in” by the architectural design at the concept stage. They often face pressure to accept inadequate dimensions carried over from previous projects and what has been gotten away with, despite clear code obligations.

Plumbing contractors bear the practical burden of installing pipework in spaces that may physically prevent compliance with fire separation and clearance requirements. Certifiers are responsible for regulating fire separation, particularly the installation of horizontal and vertical fire collars and the provision of access, but non-compliances often only become apparent at or after practical completion.

Finally, strata management deals with the long-term consequences, including Council-issued fire notices and non-serviceable systems that require destructive access and costly remediation.

“By the time a riser problem becomes visible, resolving it often involves structural modifications, legal disputes or expert-witness intervention,” David says.

The hidden costs

Non-compliant or inaccessible risers introduce a cascade of financial, structural and safety risks that affect every party involved in a building’s lifecycle. These risks don’t simply appear at handover; they continue to surface years later, often when the cost and complexity of remediation have significantly escalated.

For licensed plumbing contractors, the implications are particularly serious. They carry statutory warranty obligations for their workmanship and, in practical terms, for any compliance issues that manifest for up to seven years after completion. Even when design constraints were outside their control, they are frequently held accountable when non-compliant installations fail or become inaccessible.

Designers face their own exposure. They are required to exercise due diligence to ensure every element of their documentation aligns with AS/NZS 3500, the NCC and relevant manufacturer specifications. When risers are undersized or access provisions are omitted, the responsibility often comes back to the designer, carrying both legal liability and reputational consequences.

For developers, the financial reality can be extremely costly. Many are forced to remediate non-compliant risers after practical completion, long after contractors and certifiers have moved on.

Rectification work at this stage may require demolition of finished interiors, replumbing entire sections or re-establishing fire ratings, meaning activities that can disrupt residents and dramatically increase project costs.

Strata managers and owners then inherit the long-term operational burden. Routine maintenance tasks that should be straightforward, such as replacing valves, fire collars or pipe sections, become intrusive and expensive when risers are inaccessible.

What would normally be a simple service call may instead require wall removal, creation of temporary access points or partial reconstruction of the affected area.

Structurally, poorly fire-rated risers pose a heightened risk of fire spread, compromising the safety of building occupants. Functionally, inaccessible risers shorten the service life of hydraulic systems, increase the likelihood of failures and contribute to recurring maintenance issues that could have been avoided with compliant design from the outset.

What does this all mean for plumbers?

Plumbers have both the right and the professional obligation to refuse any installation that cannot be completed in compliance with the code. They play a critical role in identifying design oversights before they become embedded in the fabric of a building.

When confronted with insufficient space, missing access or non-compliant fire-separation requirements, plumbers should formally document the issue, issue RFI notices requesting revised designs or additional spatial allowances and seek certification advice before any work proceeds. Compliance is not optional, and contractors must not be pressured into assembling systems that are knowingly non-compliant or destined to fail an inspection.

Despite the thousands of riser-related non-compliances uncovered across the industry, many discovered only after residents have moved in, these lessons are still not feeding back into early design stages. The underlying barrier remains the commercial pressure applied at every level of the development process, which often encourages teams to accept riser footprints that are already too small from day one.

Improving outcomes requires stronger communication and clearer expectations across the industry. Mandatory concept-phase coordination between architects and hydraulic engineers would prevent many of the spatial conflicts that currently emerge late in the construction program. Regulators must consistently enforce existing access and fire-separation requirements, rather than allowing leniency that ultimately shifts risk onto contractors and building owners.

Spatial allowances for maintenance and fire compliance should be clearly documented in DA, CC and IFC drawing sets, leaving no ambiguity around the required dimensions. At a cultural level, the industry needs to recognise that maintainability is not a negotiable design feature; it is a fundamental requirement of every hydraulic installation.

Soft enforcement has proven ineffective. Only stronger regulatory intervention combined with clear, industry-wide messaging will shift the systemic behaviours that allow undersized risers to persist.

“Riser design is only one symptom of a deeper issue in the industry. Across new multi-residential buildings, a pattern of recurring, basic compliance defects continue to emerge, well understood by expert-witness engineers, certifiers and regulators,” David says.

“Despite the awareness at senior levels, meaningful reform has been slow. If the industry is to break the cycle of retrospective defect discovery, a more assertive regulatory stance is needed. Buildings must be designed with lifecycle serviceability, fire safety and compliance as foundational principles, not optional considerations sacrificed for marginal NLA gains.”

At present, there are no immediate amendments to the NCC that specifically address riser design, leaving the industry to rely on existing provisions around access, separation and maintainability to guide compliance.

David says there is growing scrutiny from regulators, auditors and insurers over how buildings are designed for longevity and long-term serviceability. If this momentum continues, industry pressure is likely to drive formal reform.