12 October 2026 Uncategorized 0

Service Riser Openings for Contractors: Check Fire Strategy First

Service riser openings must keep the fire-resisting enclosure intact at every floor, stay within permitted sizes and spacing, and get fire-stopped using tested systems referenced in the relevant codes and standards. Before any cutting begins, we always check the project’s fire-resistance level (FRL) and fire strategy, because those two documents decide exactly what each penetration is allowed to look like.

TL;DR:

Confirm the project’s FRL and fire strategy with the fire engineer before cutting, because they determine which penetration clauses and tested configurations apply.

Keep metal pipe openings neat and at least 200 millimeters apart; maintain 50 millimeters between cable or pipe openings and other services.

NCC rules cap cable openings at 2,000 square millimeters for a single cable with a gap of 15 millimeters or less, or 500 otherwise.

Plastic pipes need collars or wraps that close as the pipe fails, while metal pipes and cable bundles require systems tested for their specific configurations.

Record each penetration’s location, product data, and test evidence in a register used for inspections, future work, and compliance or insurance audits.

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What service riser openings are and why floor-by-floor closure matters
Standards that govern service penetrations
Sizing, spacing and limits for common penetrations
Firestopping methods and materials for riser openings
Design and installation checklist: plan, document, inspect
Field notes from a concrete cutting specialist
Treat riser openings as a design responsibility, not a site decision
Getting riser openings right with a specialist cutting contractor
FAQ
Sources

What service riser openings are and why floor-by-floor closure matters

A riser shaft is the continuous vertical space that carries pipework, cabling, and ductwork between floors. It differs from a service void or a framed partition cavity because it runs uninterrupted through multiple levels, which means a gap at any single floor can create a path for fire and smoke to travel well beyond its point of origin. That is why the enclosure around a riser, and the way it closes at each floor, gets specific regulatory attention rather than being left to site judgment. According to guidance on riser shaft design, the alignment of openings, the method of closing the shaft at each level, and access at every floor all need to be verified against the building’s fire strategy.

Risers commonly carry a mix of:

Hydraulic and fire services piping, including sprinkler mains and dry risers
Electrical cabling and communications conduits
HVAC ductwork and refrigerant lines
Plumbing stacks and stormwater pipework

Each of these penetrates the riser enclosure at every floor it passes, and every one of those penetrations needs to be sized, spaced, and sealed on purpose rather than cut to convenience.

Standards that govern service penetrations

Two code references do most of the work here. Specification 13 of the NCC sets out materials and methods for services passing through walls, floors, and ceilings that carry a fire-resistance level, including specific criteria for metal pipes, cable openings, and packing in hollow construction. The earlier Specification C3.15 covers similar ground and permits certain metal pipe systems that do not meet the insulation criteria of AS 1530.4, provided set conditions are met.

Alongside these, AS 4072.1 sets minimum requirements and test configurations for sealing systems around penetrations and control joints, and it is meant to be read together with AS 1530.4 fire test methods.

In practice:

Your project’s FRL and fire engineer’s strategy determine the exact clause that applies
A tested firestopping system only performs as tested when installed to match its listed configuration

Sizing, spacing and limits for common penetrations

Getting the dimensions right at the cutting stage saves rework later. Under NCC Specification 13, the rules break down roughly like this:

A single metal pipe penetration must be a neat opening, cut to size rather than oversized, and sit no closer than 200 millimeters to any other service penetration.
Each opening is generally limited to one pipe, so bundling multiple pipes through a single hole is not permitted where the rule applies.
Cable openings are capped by cross-sectional area: up to 2,000 square millimeters for a single cable where the surrounding gap is 15 millimeters or less, or 500 square millimeters for other arrangements.
Cable and pipe openings both need at least 50 millimeters of clearance from other services.
Sockets, recesses, and penetrations through hollow construction need the cavity packed in line with the specification before the opening is sealed.

Pro Tip: Mark out penetration positions on a riser coordination drawing before any cutting starts. It is far cheaper to shift a hole 50 millimeters on paper than to patch and refire-rate one on site.

Firestopping methods and materials for riser openings

Once an opening is cut to the correct size, the firestopping system does the real work of restoring the fire-resistance level. Common approaches include:

Mineral wool packing compressed into the annulus around pipes and cables
Intumescent sealants that expand under heat to close small gaps
Fire collars and wraps fitted around plastic pipes, which soften or burn through during a fire
Proprietary modules and bricks for larger or mixed-service openings

Metallic and plastic pipes are treated differently under the standards, because plastic pipes lose integrity in a fire and need a device that closes the opening as the pipe collapses, while metal pipes typically rely on packing and sealant alone. Cable bundles usually need a different tested system again, since the cable jacketing and bundle density affect how the seal performs.

Pro Tip: Keep the annulus around each penetration as small as the tested system allows. A tidy, minimal gap is easier and cheaper to fire-stop than an oversized one, and it is more likely to match the exact configuration the system was tested under.

Installation best practice follows the same logic throughout: cut neat holes, use the minimum annulus the tested system specifies, and fit any required flange or collar exactly where the test report shows it.

Design and installation checklist: plan, document, inspect

A compliant riser opening starts on the drawing board and ends with a record someone can check years later, which is crucial when working with fire-rated partitions to maintain building safety. We find the process holds together best when it follows a clear sequence:

Confirm the FRL and fire strategy with the project’s fire engineer before any penetration is finalized.
Coordinate riser layout early between trades, as Walraven’s guide to riser design notes, to avoid oversized or misaligned openings that force complex firestopping fixes later.
Form neat, correctly sized holes and maintain the required clearances from other services.
Install the tested firestopping system to its listed configuration, not an approximation of it.
Record each penetration with its product data sheet, test evidence, and location on an as-built register.

On handover, that register becomes the reference point for:

Periodic inspections required under the building’s fire safety schedule
Any future trade needing to penetrate the same riser without compromising existing seals
Insurance or compliance audits that ask for proof of installation

Field notes from a concrete cutting specialist

Precision at the cutting stage makes every later step easier. When a hole is drilled or sawn to the exact diameter a firestopping system is tested for, the installer is not fighting an oversized annulus or patching around a ragged edge. Core drilling, in particular, produces the clean, round openings that most pipe penetration seals are designed around, and wall sawing gives a straight, controlled edge for larger or linear openings.

We coordinate directly with firestop installers before cutting begins, confirming exact diameters and positions so nobody discovers a mismatch after the concrete is already open. Working on fire-resisting elements also means strict OH&S controls: dust suppression, structural assessment before cutting near rebar or post-tensioned cable, and isolation of any live services in the path.

Practical coordination like this applies equally to HVAC penetrations and to electrical and plumbing drilling work, where the same precision keeps firestopping straightforward rather than improvised.

Treat riser openings as a design responsibility, not a site decision

We think the biggest risk in riser design is treating openings as something to sort out on site rather than something decided on a drawing. An undocumented change, a hole cut 20 millimeters oversized, or a pipe routed through a gap never assessed for fire performance can quietly undo a building’s entire fire strategy. Early coordination and a complete penetration register are not paperwork for its own sake. They are what let anyone, years later, confirm the enclosure still does what it was designed to do.

— MYBMC

Getting riser openings right with a specialist cutting contractor

Clean, accurately sized openings make every later step, from firestopping to inspection, straightforward instead of improvised. We bring precision to riser and penetration work through:

Core drilling for neat, round pipe and cable penetrations sized to match tested firestopping systems
Wall sawing for larger or linear openings with straight, controlled edges
Coordination with firestop installers before cutting, so annulus sizes and positions are confirmed in advance

A smaller, accurate annulus means less packing, less rework, and a seal that matches its tested configuration rather than approximates it. If you have a riser project coming up, get in touch for a site quote and we will work through the opening sizes and positions against your fire strategy before anyone picks up a drill.

FAQ

How does a dry riser work?

A dry riser is a vertical pipe installed within a building, normally empty of water, that firefighters connect to a pumping appliance at ground level to supply water to upper floors during an emergency. It runs through the riser shaft alongside other services, which is why its penetrations at each floor need the same fire-stopping attention as any other service passing through a fire-resisting enclosure.

What does riser mean in construction?

In construction, a riser is a continuous vertical shaft or duct that carries services such as pipework, cabling, and ductwork between floors of a building. Because it runs uninterrupted through multiple levels, its enclosure and closure at each floor are treated as a regulated fire-safety element rather than an ordinary service void.

Where are fire risers located?

Fire risers are typically located in a dedicated vertical shaft, often near a building’s main stairwell or service core, so firefighting water supply can reach every floor efficiently. Exact placement depends on the building’s fire strategy and layout, which is why riser positions are set at design stage rather than decided on site.

What governs penetrations through a fire riser’s walls or floors?

Penetrations through a fire riser’s fire-resisting walls or floors are governed by provisions such as NCC Specification 13 and AS 4072.1, which set sizing, spacing, and sealing requirements for pipes, cables, and conduits. The exact requirements that apply depend on the building’s specific FRL and fire strategy, so they should be confirmed with a fire engineer before work begins.