A required sprinkler system is a cost. The National Construction Code’s answer to that cost is a set of concessions: longer walks to an exit, thinner fire-resisting construction, bigger compartments, and in a few residential cases a quieter hydrant arrangement. Used early, those concessions can pay for the pipe. Used late, they are a footnote on a building that has already been drawn the expensive way.
This article is about what the concessions actually are, what they are worth in Australian project terms, and when a fire engineer is still writing a performance solution anyway. It belongs with when the NCC requires sprinklers and the FPAA101D / 101H / AS 2118.4 choice in standards and compliance.
Two cautions before the list. First, concessions attach to a required automatic sprinkler system that meets the nominated standard. A few heads in a lobby do not unlock Part C and Part D. Second, numbering moves. NCC 2022 talks about Specification 18 for mid-rise Class 2 and 3 buildings and about Type-of-construction and compartment clauses elsewhere. NCC 2019 said Specification E1.5a. Check the adopted edition.
What concessions do sprinklers unlock?
Think in three piles: mid-rise residential (Specification 18), general DTS trade-offs that have been in the Code for years, and things people assume are concessions but are not.
Mid-rise Class 2 and 3 — Specification 18
For a building that is only Class 2 or 3, not more than 25 m effective height, four or more storeys, and sprinkled to Specification 17 and 18, the Code gives a published list. The list is not identical for AS 2118.1 / AS 2118.4, for FPAA101D, and for FPAA101H. In 2022 terms the recurring items are:
- Travel distance inside a sole-occupancy unit, from 6 m to 12 m.
- Single-exit travel at the storey that leaves to a road or open space, from 20 m to 30 m.
- Distance between alternative exits, from 45 m to 60 m.
- Fire-resistance level reductions on nominated non-loadbearing walls, shafts, fire doors and, in some cases, fire-isolated stair enclosures — figures such as –/45/45 or –/60/60 instead of the unsprinklered Specification 5 numbers.
- Window-opening protection relief on some FPAA pathways where the room itself is sprinkled.
- Internal hydrant relief: omit internal hydrants if complying external hydrants cover the building, or provide a dry hydrant system with a booster and a street hydrant within 60 m.
That hydrant clause is the one everyone remembers and the one that is most often misapplied. Fire and Rescue NSW’s published position is blunt: Specification 18 concessions, including the dry hydrant concession, apply to Class 2 or 3 only. A shop, an office, a gym or a basement car park that makes the building multiple classification takes you out of that concession set even if 101D or 101H is still a legal sprinkler standard.
Commercial and general DTS
Outside that mid-rise residential pathway, sprinklers have been trading against construction for a long time:
- Larger fire compartments. Type A, B and C construction tables allow more floor area and volume when the building is sprinkled. This is how a warehouse becomes a large isolated building rather than a row of fire walls.
- FRL reductions in Specification 5 for particular elements — car-park concessions, timber mid-rise Class 2 and 3, residential-care concessions — that are written on the basis that Specification 17 sprinklers are present.
- Smoke-hazard management options that assume a sprinkled fire is a smaller fire.
- Atrium and some opening-protection rules that become workable only with sprinklers.
These are not a free upgrade. They are the Code saying the design fire is now the sprinkled fire. If you then omit heads in a concealed space or a loaded balcony that the Standard or Specification 17 wanted covered, you have also omitted the reason the FRL was reduced.
What sprinklers do not automatically buy
- A hydrant-free commercial building. Sprinklers, hydrants and hose reels remain separate E1 systems. AS 2419.1 does not retire because AS 2118.1 arrived.
- A hose-reel holiday in every class. Some pathways relax occupant firefighting equipment; many do not.
- A performance-solution holiday. Concessions are DTS. The moment you want a travel distance, an open stair or a timber detail that is still outside the concession, you are in fire engineering.
- A weaker water supply. Concessions assume the sprinkler system works. They are not compensation for an unproved town main.
How much are those concessions worth?
Worth, here, means construction cost avoided, not a moral argument about safety. The ABCB already made the safety argument when it mandated mid-rise sprinklers.
On the Board’s six-storey hotel test case, FPAA101D plus concessions undercut the unsprinklered NCC 2016 DTS building by about 1.7 per cent of project cost. FPAA101H was about 3.2 per cent dearer. AS 2118.1 or AS 2118.4 about 4.6 per cent dearer. Donald Cant Watts Corke’s supporting cost work for the Board described many Class 2 and 3 examples as near cost-neutral once offsets were traded — often inside plus or minus one per cent of project value.
Those offsets are not mysterious. They are, in ordinary Australian tender language:
- Fewer or slimmer fire walls and shafts, because FRLs dropped or compartments grew.
- A more efficient floor plate, because 12 m and 30 m and 60 m are real metres on a narrow site.
- One less stair in some layouts, or a stair that no longer eats the middle of the plate.
- Cheaper doors and penetrations where –/45/45 or –/30/30 is legal.
- Less hydrant pipe, fewer in-building hydrant cupboards, no wet riser — but only on the Specification 18 path that actually allows it.
- Timber mid-rise becoming a DTS conversation rather than a one-off alternative solution.
They are also easy to lose. The classic ways to lose them:
- Fixing the core and the stairs before the sprinkler standard is chosen.
- Assuming Specification 18 applies to a mixed-use building.
- Banking a hydrant omission the fire service will not support.
- Forgetting that care buildings and early childhood have their own, tighter rules.
- Counting a concession twice — once in the feasibility spreadsheet and once in a later performance solution that the surveyor never accepted.
If you need a single working rule: price the sprinkler standard and the concessions as one fire strategy. Pricing the heads against last year’s unsprinklered building, then discovering you still need the old stairs, is how 101D becomes dearer than AS 2118.1.
When do you still need a performance solution?
DTS concessions are a closed list. A fire engineer still appears when the building wants something the list does not give.
Typical cases:
- travel distances beyond even the sprinkled figures
- an open or scissor stair the DTS tables will not wear
- a mixed-use building that wants Specification 18 concessions FRNSW and the Code do not give it
- a heritage or existing building where you cannot install the system Specification 17 describes
- a warehouse layout that needs compartment sizes or smoke measures beyond the sprinkled tables
- any attempt to reduce sprinkler coverage below the nominated standard and still keep the concessions
A performance solution is a report, a set of acceptance criteria, and a certifier who is prepared to accept it. It is not a sentence in a meeting. If the concessions you need are already in Specification 18 or Specification 5, spend the fee on a proper AS 2118 or FPAA design instead of an alternative solution that re-argues the Code.
Why water authority capacity can undo the cost case
Every cheerful ABCB percentage assumes water comes out of the street at the rate the chosen specification needs. That is the fragile assumption.
FPAA101D needs a domestic service that can still run the remote sprinkler area when people are home. FPAA101H and AS 2118.1 need a fire service, which may be the same main or a dedicated tank. Water authorities are not a party to your concession spreadsheet. They will say no, or they will say yes with a pressure that only works at 11 p.m., or they will require on-site storage that brings back the pump room you thought you had designed out.
The order of operations that keeps projects honest is:
- Classify the building and pick the legal sprinkler standards, not the preferred one.
- Ask the water authority for written flow-and-pressure information at the proposed connection, for the duration the standard wants.
- Only then draw the stairs, the FRLs and the hydrant omission.
- Hold a contingency for a tank and pump until that letter exists. A 20,000 or 50,000 litre tank, an electric pump and a diesel spare will erase a 1.7 per cent saving without raising its voice.
- Do not let a planning report tell purchasers the building is “sprinklered with DTS concessions” before step 2.
Concessions are worth money. They are not worth a redesign in week forty. The cheaper sprinkler standard is the one whose water supply and whose concession set both survive contact with the street main, the fire service and the building that is actually being built.