NCC 2025 Corrigendum 1: What the ABCB Corrected (October 2026)
On 29 October 2026 the ABCB issued Corrigendum 1 to NCC 2025. Most corrections are editorial, but several change a result: Class 8 joins the solar PV tables, a sign error in the Volume Three pipe sizing method is gone, and the Housing Provisions steel, Class 10b and glazing provisions are corrected. Every correction, clause by clause.
On 29 October 2026 the Australian Building Codes Board issued Corrigendum 1 to NCC 2025. The ABCB calls the corrections editorial, and most are: a wrong cross-reference here, a mislabelled row there. A few still change the answer you would get, so here is every correction, what it fixes and who should check their work.
In one minute
Solar PV: Tables J9D5a and J9D5b now include Class 8. The figures did not change.
Plumbing: the B1V1 method for sizing cold-water pipes in Class 2 and 3 buildings had a sign error in two exponents. As published, the chance of a shower running at peak rose with the number of apartments. Corrected, it falls.
Houses: corrosion protection on its own is no longer listed as a way for structural steel to comply, and strutting beams now sit within the Part 6.3 limits. The AS 1657 option for platforms and ladders is limited to a mast, antenna, tower or the like. A frame factor row in Table 13.3.2ae is relabelled ≤ 0.40.
The rest are cross-references and notes: Class 1b holiday dwellings, smoke protection for exits in atrium buildings, two rows of the referenced documents schedule, and B2V1.
NCC 2022 Amendment 2 has its own corrigendum, issued the same day.
Every correction at a glance
| Provision | What the correction does |
|---|---|
| A6G2, explanatory note (all volumes) | Compares the two kinds of Class 1b building. It had compared Class 1b with Class 1a. |
| Schedule 2, AS 3600 | Lists Housing Provisions 2.2.4 among the provisions that call up AS 3600. |
| Schedule 2, AS 4654 Part 2 | No longer lists F1D5, which calls up AS 3600 for concrete. |
| Volume One S31C21 | Required fire-isolated exits in a building containing an atrium are protected from smoke under Part E2. It had pointed to E2D3, which covers air-handling systems. |
| Volume One J9D5 | Adds Class 8 to Tables J9D5a and J9D5b. |
| Volume Two H1D6(5) | Makes Part 6.3 (strength) and 6.3.9 (corrosion protection) one option. 6.3.9 had been listed as an option on its own. |
| Housing Provisions 2.2.4(1)(d) | Concrete construction: H1D4 or AS 3600 as applicable. It had named H1D4 only. |
| Housing Provisions 6.3.1(1) | The clause outside the H1D6(6) limits is 6.3.9, corrosion protection. It had said 6.3.4, strutting beams. |
| Housing Provisions 11.2.7 | The AS 1657 option covers a Class 10b mast, antenna, tower or the like. It had covered any Class 10b structure. |
| Housing Provisions Table 13.3.2ae | The first frame factor row is for a solar absorptance of ≤ 0.40. It had repeated the > 0.40 to < 0.68 label. |
| Volume Three B1V1(6) and (8) | Removes the minus sign from the exponents c2 and c4. |
| Volume Three B2V1 | Verifies compliance with B2P7. It had said B2P6. |
NCC 2025 Corrigendum 1 (ABCB, version 1.0, 29 October 2026), read against the published NCC 2025 text. The Housing Provisions' list of amendments is corrected to match 11.2.7.
What changed in the solar PV requirements?
J9D5(2) requires a building to have an on-site solar PV system. It can cover 100% of the roof, less the areas J9D5(2) excludes, or reach a minimum peak output per m² of conditioned space from Table J9D5a. Where gas is used for building services, Table J9D5b adds further output (J9D5(3)).
Both tables listed Class 5, 6 and 7, and Class 3 and 9. Class 8 was missing, so a factory, workshop or laboratory had no figure for the output route. The corrigendum puts Class 8 in the first row. The numbers are unchanged:
| Building class | Climate zone 1 | Zones 2 to 7 | Zone 8 |
|---|---|---|---|
| Class 5, 6, 7 and 8 | 95 | 65 | 55 |
| Class 3 and 9 | 70 | 40 | 35 |
Table J9D5a as corrected: minimum installed peak output, in W per m² of conditioned space, for a building without gas. In Table J9D5b, Class 8 joins the same row: 0, 0, 1, 1.7 and 4.7 W/m² across its five climate zone columns.
If you prepared a Section J report for a Class 8 building on the output route, check which figure it used.
What was wrong with the Volume Three pipe sizing formula?
B1V1 is a Verification Method for sizing the cold-water service of a Class 2 or Class 3 building. It works out a 99th percentile flow rate from the probability that each kind of fixture is running at peak. That probability depends on how many apartments, and how many occupants, draw water downstream of the pipe (B1V1(5) to (8)).
As published, B1V1(6) raised the number of apartments to the power of −c2, and B1V1(8) to −c4. In Table B1V1 every c4 and every non-zero c2 is already negative (c2 is −0.475 for a shower), so the two minus signs cancelled. The probability of use then grew with the building, when the method intends the reverse: in a bigger building, any one shower is less likely to be running at the peak. The corrigendum removes the minus signs.
A higher probability means a higher design flow and a larger pipe. If you used B1V1 for a Class 2 or 3 cold-water service, run the calculation again.
What changed for houses and the Housing Provisions?
Structural steel (H1D6(5) and 6.3.1). H1D6(5) lists the ways structural steel sections satisfy H1P1: AS 4100, AS/NZS 4600, or the Housing Provisions. It had also listed 6.3.9 (corrosion protection) as a separate item, as if corrosion protection alone satisfied H1P1. Part 6.3 (strength) and 6.3.9 are now one option with two parts, H1D6(5)(c). In 6.3.1(1), the clause free of the H1D6(6) limits (wind class N3 or less, even loads, no snow loads and the rest) is now 6.3.9. It had named 6.3.4, so strutting beams now sit within those limits like the rest of Part 6.3.
Concrete (2.2.4(1)(d)). Concrete construction now reads "H1D4 or AS 3600 as applicable", and the referenced documents schedule lists 2.2.4 against AS 3600.
Class 10b platforms and ladders (11.2.7). 11.2.7, which lets a fixed platform, walkway, stair or ladder be built to AS 1657, now applies only to one serving a Class 10b mast, antenna, tower or the like. It had covered any Class 10b structure, a class that also takes in fences, retaining walls and swimming pools (A6G11).
Glazing in climate zone 6 (Table 13.3.2ae). The winter solar heat gain table listed the frame factor for a solar absorptance of > 0.40 to < 0.68 twice, with different values. The first row, 0.93 for a floor on the ground and 0.83 for a suspended floor, is for frames of ≤ 0.40. A mid-coloured frame takes 0.96.
Does the corrigendum change Class 1b holiday accommodation?
No. It corrects the explanatory note under A6G2, not the provision. The note now contrasts the two kinds of Class 1b. A boarding house, guest house or hostel is Class 1b only up to 12 people and 300 m² (A6G2(2)(b)(i)). Four or more single dwellings on one allotment used for short-term holiday accommodation are Class 1b whatever their floor area (A6G2(2)(b)(ii)). The note had set Class 1b against Class 1a.
The other corrected references in the table above (S31C21, Schedule 2 and B2V1) now point to the right place. A specification or report that copied an old reference should be updated.
Is there a corrigendum for NCC 2022?
Yes. The ABCB issued NCC 2022 Amendment 2 Corrigendum 1 the same day, because some of the corrected provisions appear in both editions. It carries the corrections common to both: the Class 1b note, the AS 3600 row, S31C21, H1D6, Housing Provisions 2.2.4 and 6.3.1, and the glazing row. The solar PV, Class 10b, AS 4654 Part 2 and Volume Three corrections are in the NCC 2025 corrigendum only.
What should you do now?
Keep the corrigendum with your copy of NCC 2025, or check that the copy you work from already carries the corrections.
Re-check work that relied on the corrected text: J9D5 for a Class 8 building, B1V1 pipe sizing, the Housing Provisions route for structural steel, and frame factors from Table 13.3.2ae.
Update templates and specifications that cite E2D3 for exits in an atrium building, or list AS 4654.2 against F1D5.
Sources: ABCB, Updated NCC publications now available (29 October 2026); NCC 2025 Corrigendum 1 and NCC 2022 Amendment 2 Corrigendum 1, version 1.0; NCC 2025 Volumes One, Two and Three and the ABCB Housing Provisions.
Questions this guide answers
What is NCC 2025 Corrigendum 1?
A correction document the Australian Building Codes Board issued on 29 October 2026. It fixes errors found in NCC 2025 since publication, across Volumes One, Two and Three and the ABCB Housing Provisions. The ABCB describes the corrections as editorial, although several of them change a result.
Does the corrigendum change the solar PV requirements in J9D5?
It adds Class 8 to Tables J9D5a and J9D5b, which listed only Class 5, 6 and 7, and Class 3 and 9. A Class 8 building without gas now reads 95, 65 or 55 W of peak output per m² of conditioned space in climate zone 1, zones 2 to 7 and zone 8. The figures themselves did not change.
What was wrong with the B1V1 pipe sizing formula in Volume Three?
B1V1(6) and B1V1(8) raised the number of apartments to the power of minus c2 and minus c4. In Table B1V1 every c4 and every non-zero c2 is already negative, so the probability of fixture use rose with the size of the building instead of falling. The corrigendum removes the minus signs. For a shower downstream of 20 apartments, the published formula gave about 17 times the corrected probability.
Does the corrigendum change how Class 1b buildings are classified?
No. It corrects the explanatory note under A6G2. A boarding house, guest house or hostel is Class 1b only up to 12 people and 300 m², while four or more single dwellings on one allotment used for short-term holiday accommodation are Class 1b whatever their floor area. The provision itself is unchanged.
Is there a corrigendum for NCC 2022?
Yes. The ABCB issued NCC 2022 Amendment 2 Corrigendum 1 on the same day, with the corrections common to both editions. The solar PV, Class 10b, AS 4654 Part 2 and Volume Three corrections are in the NCC 2025 corrigendum only.
