Most older buildings in Auckland that fail a passive fire inspection do not fail because of the walls. They fail because of what passes through them. Plumbing, power, data and ventilation added over decades, bundled through the same hole, with no tested fire stopping system that covers the arrangement. This article explains why those penetrations fail, why the obvious fix usually does not work, and what a compliant repair looks like.
What a mixed service penetration is
A single pipe through a fire-rated wall is a simple penetration. A tested system exists for it: a collar for plastic, mastic and insulation for metal, each proven in a furnace test for that pipe size and wall type.
A mixed service penetration is anything else. Typically:
- Several services of different types through one opening: a PVC waste, a copper water line, a bundle of data cables and a conduit, all touching.
- An oversized or irregular hole, cut wider than the services needed and never made good.
- Services added after the original fire stopping, pushed through the existing seal.
- Cable trays with cables added year after year until the tray is overfull.
In buildings from the 1970s to the early 2000s, this is normal. The services were installed by different trades over years, and either nobody was responsible for the fire stopping or the standard at the time did not require what it does now.
Why they fail inspection
Fire stopping only counts when it matches a tested system. The manufacturer tests a product in a furnace with a specific wall, a specific service, a specific size and a specific gap. The result is a rating for that exact arrangement.
Nobody tests every combination. There is no furnace test for a 100 mm PVC pipe touching a 25 mm copper pipe touching forty data cables through a 300 mm hole in a 1985 concrete block wall. So there is no product you can apply to that opening and call it rated. An IQP inspecting for the Building Warrant of Fitness will list it as a defect, because it is one, regardless of how much mastic has been pumped into it.
That is also why the defect tends to appear suddenly. Inspection has tightened. IQPs now work to a code of practice that classifies large openings and untested seals around penetrations as critical defects, and they will not issue the Form 12A until they are fixed. A building that passed for years can fail the next one on the same penetrations.
Why collars and mastic alone do not work
The first instinct is to fit a collar and seal the rest with fire-rated mastic. On a mixed penetration this usually makes things worse, for three reasons.
- The collar is not tested for it. Collars are tested on a single pipe, centred in a hole of a set size, with a set gap. A collar around a plastic pipe that is touching a copper pipe and a cable bundle is outside its test. It may not close properly when the pipe melts, and the metal services beside it will still conduct heat.
- Mastic has depth and gap limits. Every fire-rated mastic has a maximum gap it can bridge and a minimum depth it needs. A 40 mm void filled with 10 mm of mastic has no rating.
- Metal services still need insulation. Sealing the gap does nothing about heat travelling along a copper pipe or steel tray into the next room. See heat transfer in fire safety.
An installation that is not to a tested system will fail the next inspection just as the original did, and now the owner has paid twice.
The fix: bring the opening back inside a tested system
The aim is always the same: change the opening, or the way the services pass through it, so that a tested system applies. In practice there are three routes, and we use them in this order.
Use a system tested for mixed services
This is the first place to look, and it covers more situations than most people expect. The range of tested systems has grown a lot in the last few years. Manufacturers now hold test evidence for mixed-service openings: batt and mastic systems with plastic and metal pipes, cable bundles and trays passing through together, with tested rules for spacing, annular gaps, insulation length and maximum opening size. Where the existing penetration can be brought within one of those scopes, sometimes just by repositioning a service or trimming a hole, it is sealed to that system and it is compliant.
Rebuild the opening
Where the opening itself is the problem, oversized, irregular, or cut through a substrate that is not part of any test, the hole is made good first. The opening is cleaned out and reduced or reframed to a size and construction that a tested system covers, then closed with a mineral wool fire batt cut tightly around each service. Each service is treated individually where it passes through: collars on plastic pipes, mastic and insulation on metal, and cables sealed and separated to the tested spacing.
Bulkheads, where nothing else fits
A bulkhead, sometimes called a fire box, is a framed enclosure lined with fire-rated plasterboard, built around a cluster of services so that they can be fire stopped through its lining instead of through the original wall or floor. It has a place, mostly at large slab core holes in risers and plant rooms where the services cannot be separated and the original substrate cannot be sealed to. It is also the option most often reached for as a cheap retrofit, and it should not be the default. A bulkhead adds a new element to the building that has to be built, lined and detailed to a tested system in its own right, and it is usually more work than bringing the original opening within a tested scope.
What the repair should leave behind
The work is only half the job. A compliant repair on a mixed penetration should leave the owner with:
- A tag at the penetration naming the system, the rating, the installer and the date.
- Before and after photographs.
- An entry in the building’s penetration register.
- The test report or appraisal reference for the system used, so the IQP can verify it.
Without that record, the next IQP has no way to confirm what was done, and the penetration is back on the defect list.
Frequently asked questions
Why did my building pass inspection before and fail now?
IQPs now work to a code of practice that treats untested penetration seals and large openings as critical defects. Inspection standards have tightened and above-ceiling checks are more thorough than they were.
Can I just add more fire mastic?
Not on a mixed penetration. Mastic has tested gap and depth limits, and it does nothing about heat conducted along metal services. It will fail the next inspection.
What is a bulkhead in passive fire?
A fire-rated enclosure built around a cluster of services, framed and lined with fire-rated plasterboard to the same rating as the wall or floor. It is one option for openings that cannot be brought within a tested system any other way, not the default fix.
How much does it cost to fix a mixed penetration?
A single opening sealed to a tested multi-service system, or rebuilt and sealed, is usually a few hundred to a couple of thousand dollars depending on access and services. The larger cost in older buildings is the number of penetrations, which is why we inspect and register them all before quoting.
Will the fix need a PS3?
If the work is under a building consent, yes. For BWOF remediation, the IQP will want documentation of the tested system used at each penetration.
Do you work outside Auckland?
Yes. Auckland, Northland and North Waikato.
Talk to a passive fire specialist
If an IQP has flagged mixed penetrations, or you manage an older building and want them registered before the next inspection, get in touch or call 021 288 1701. Read what happens when your BWOF passive fire inspection fails and see passive fire remedial works for how we approach remediation.