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AS 2870 vs NCC 1
- Thread starter LiamJS
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- #2
Retrograde
Structural
What are the actual disrepancies? Which tables in particular are you talking about?
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- Thread starter
- #5
Thank you for your answers.
For example :
Stiffened Raft Class S Articulated Full Masonry: AS2870 Figure 3.1=500mm vs NCC 2019 Table 3.2.5.4b = 400mm
Another example:
Stiffened Raft Class M Full Masonry: AS2870 Figure 3.1=950mm vs NCC 2019 Table 3.2.5.5a = 800mm
There are others but I gave two examples. Another thing is that the standard is in "Pending Revision" status, and this makes things more confusing.
For example :
Stiffened Raft Class S Articulated Full Masonry: AS2870 Figure 3.1=500mm vs NCC 2019 Table 3.2.5.4b = 400mm
Another example:
Stiffened Raft Class M Full Masonry: AS2870 Figure 3.1=950mm vs NCC 2019 Table 3.2.5.5a = 800mm
There are others but I gave two examples. Another thing is that the standard is in "Pending Revision" status, and this makes things more confusing.
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- #6
Retrograde
Structural
I confess that I had no idea those tables are in the NCC. I have always just used AS 2870.
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- #8
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1
- #9
The NCC and Australian Standards are written by different groups who have different opinions and different goals.
Regarding the tables, I remember the divergence started with AS2870-2011. If you look at the earlier versions of AS2870 then they should be the same. You would have to confirm this, but I remember there being some big drought in the eastern states which caused cracking of walls on clay sites and this led to AS2870 designs becoming heavier. I think the NCC may have disagreed with the change and left it as is.
Most companies I know kept the original design that they had been using for decades and didn't follow the upgrade.
Hope this helps.
Regarding the tables, I remember the divergence started with AS2870-2011. If you look at the earlier versions of AS2870 then they should be the same. You would have to confirm this, but I remember there being some big drought in the eastern states which caused cracking of walls on clay sites and this led to AS2870 designs becoming heavier. I think the NCC may have disagreed with the change and left it as is.
Most companies I know kept the original design that they had been using for decades and didn't follow the upgrade.
Both the NCC tables and AS2870 are deemed to comply. Therefore following those tables is not mandatory.
Hope this helps.
- Thread starter
- #10
Thank you for the background story. That explains the confusion. Existence of two deemed to comply solution is really messed up. Then one should do calculations to go below any of them.
Another point is about which one is binding legally. While engineering part is not clear, legal part will be more confusing. They should solve this as soon as possible.
Neither of them are legally binding since they are both deemed to satisfy solutions. Unfortunately the structure of the NCC and the law is not taught in university. I would recommend reading up on Part A2 of the NCC (including "expert judgement") as it will put you ahead of at least 90% of engineers
Not quite same but I take BPEQ case below to be requiring 2870 with no room for judgement. Recommendation treated as mandatory requirement. Sounds like footings had no actual problem.
bpeq.qld.gov.au
Board v A
An engineer is reprimanded for unsatisfactory professional conduct in preparing slab and footing designs
bpeq.qld.gov.au
The board says that his design was inadequate but the same design on the same soil profile built 5 years ago was adequate? Am I reading that correctly? Regardless, it probably comes down to details and the defense of the engineer. If the engineer's defense was that the design complied with AS2870 but it did not then that's one thing. But if the engineer designed based on first principles and expert judgement then the defense argument may be different.
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I do not know more than that webpage. Remember it from the monthly newsletter. You are right that it is missing details when it is supposed to be educating us but leaves more questions than answers. Maybe 5 year designs were AS2870 for E site and engineer thought overkill. Also not clear who complained and why but it is clear it was still performing okay for class E. So I take it as 2870 being minimum in QLD not just deemed to comply.
- Thread starter
- #15
The problem is that engineering is not respected enough even in the minds of people who live in those buildings. They see the time and money spend for a Structural Engineer is a waste. You are building something with a 50-year lifetime cycle and having the cheapest engineering is okay.
This is the definition from the media release from WA government, if you search you can find it, here: "Expert Judgement involves the use of subjective judgement that may not necessarily be supported by any technical calculations. This judgement is based on the experience of an expert using reference material and documents to support a conclusion and is usually applied where the Performance Requirements are difficult to quantify." Yeah the most perfect expert here is the one guess it without spending any time or resource. But it is not someone who requires a soil report and model the soil by springs and consider the soil-structure interaction and decide the cracking level of above members. Nah not attractive. Let the provisions conflict each other. Let the lawyers have the job flow.
This is the definition from the media release from WA government, if you search you can find it, here: "Expert Judgement involves the use of subjective judgement that may not necessarily be supported by any technical calculations. This judgement is based on the experience of an expert using reference material and documents to support a conclusion and is usually applied where the Performance Requirements are difficult to quantify." Yeah the most perfect expert here is the one guess it without spending any time or resource. But it is not someone who requires a soil report and model the soil by springs and consider the soil-structure interaction and decide the cracking level of above members. Nah not attractive. Let the provisions conflict each other. Let the lawyers have the job flow.
Retrograde
Structural
I'm no lawyer, but my understanding is that in Queensland, the NCC is legally binding because it is referenced in and given effect by the Building Act 1975 and the Plumbing and Drainage Act. This is similar for other states and their legislation.
The Australian Standards then have legal standing because they are referenced in the NCC.
On that basis the NCC has precedence over Australian Standards.
The Australian Standards then have legal standing because they are referenced in the NCC.
On that basis the NCC has precedence over Australian Standards.
Just Some Nerd
Structural
This is the way I understood it here in NSW too. Not familiar with the section OP is asking about however, I mostly work on Class II projects
Yes, it is mandatory to comply with the NCC. I should clarify that I was only talking about the deemed to satisfy table that the OP was referencing. The mandatory part of the NCC is the performance requirements.
@LiamJS
I agree with you and I'm not saying to not follow the NCC footing table or AS2870. I do the same for footing designs. I'm just trying to explain the background of the argument to help you decide which option to choose. If someone asks why you followed the NCC table and not the AS2870 table and threaten to sue you what do you say?
- Thread starter
- #19
I did some reading and will write down the outcome here, showing the reasoning chain for the tables of AS 2870 to be considered a legal deemed-to-satisfy solution in seven quotes. After that, there will be a discussion section and a conclusion. Please provide your feedback. This has been a confusing topic, and I hope this will help interested readers as well.
Reasoning Chain Demonstrating that AS 2870 is Legally Binding and Providing Deemed-to-Satisfy Provisions:
Quote 1-) Document: Western Australia Building Act 2011 Building Regulations 2012
Building Regulations 2012 - [04-j0-01].pdf
“Building Code means the Building Code of Australia which is Volumes One and Two, as amended from time to time, of the National Construction Code series published by, or on behalf of, the Australian Building Codes Board”
Quote 2-) Document: NCC 2019-A1 – Part A2
“A2.0 Compliance
Compliance with the NCC is achieved by complying with—
(1) the Governing Requirements of the NCC; and
(2) the Performance Requirements.”
Quote 3-) Document: NCC 2019-A1 – Part A2
“A2.2 Performance Solution
(1) A Performance Solution is achieved by demonstrating—
(a) compliance with all relevant Performance Requirements; or
(b) the solution is at least equivalent to the Deemed-to-Satisfy Provisions.”
Quote 4-) Document: NCC 2019-A1 – Part A2
“Part A2 Compliance with the NCC
Introduction to this Part
This Part explains the possible methods of demonstrating compliance with the NCC.”
Quote 5-) Document: NCC 2019-A1 – Part A2
“A2.3 Deemed-to-Satisfy Solution
(1) A solution that complies with the Deemed-to-Satisfy Provisions is deemed to have met the Performance Requirements.
(2) A Deemed-to-Satisfy Solution can show compliance with the Deemed-to-Satisfy Provisions through one or more of the following Assessment Methods:
(a) Evidence of suitability in accordance with Part A5 that shows the use of a material, product, plumbing and drainage product, form of construction or design meets a Deemed-to-Satisfy Provision.
(b) Expert Judgement.”
Quote 6-) Document: NCC 2019-A1 – Part A5
“A5.2 Evidence of suitability — Volumes One and Two
…
(2)Evidence to support that a calculation method complies with an ABCB protocol may be in the form of any one, or any combination of the following:
(a) A certificate from a professional engineer or other appropriately qualified person that—
(i) certifies that the calculation method complies with a relevant ABCB protocol; and
(ii) sets out the basis on which it is given and the extent to which relevant standards, specifications, rules, codes of practice and other publications have been relied upon.
(b) Another form of documentary evidence that correctly describes how the calculation method complies with a relevant ABCB protocol.”
Quote 7-) Document: NCC 2019-A1 – Part H1
“Deemed-to-Satisfy Provisions
H1D4 Footings and slabs
(1)Performance Requirement H1P1 is satisfied for the design and construction of footings and slabs if they comply with either (a) or (b):
(a) One of the following:
AS 2870.
AS 3600.
(b) Subject to (2), Section 4 of the ABCB Housing Provisions.”
DISCUSSION:
(i) Interestingly, the NCC tables under H1P1 (Quote 7) do not reference their own tables as Deemed-to-Satisfy provisions. However, Quote 2 states: “Compliance with the NCC is achieved by complying with (1) the Governing Requirements of the NCC; and (2) the Performance Requirements.”
So, what happens if there are discrepancies between the tables in AS 2870 and those in the NCC? For example, the stiffened raft height on a Class S site for articulated full masonry is listed as 500 mm in AS 2870 (Figure 3.1), while 400 mm is given in the NCC (Table 3.2.5.4b).
If we refer to the note at the beginning of Part 3.2.5 Footing and Slab Construction, it states: “The footings included in this Part reflect the requirements of AS 2870.” This clearly indicates that the NCC tables are derived from AS 2870. Therefore, in the event of a conflict, the original reference, AS 2870, should take precedence.
On the other hand, if for the cases if NCC more conservative than AS 2870 and since NCC is also legally binding NCC values should be used. This is the case for slab reinforcements.
(ii) Can an expert override a Deemed-to-Satisfy provision? According to NCC A2.3(2)(b) (Quote 5), an expert can demonstrate that a solution meets a Deemed-to-Satisfy provision using expert judgement. However, it is important to distinguish that while an expert can demonstrate compliance with a Deemed-to-Satisfy provision using alternative methods, they cannot override or change the provisions themselves.
To use footing heights smaller than those given in AS 2870, one must adopt a Performance Solution and this doesn’t have to be done by an expert. But it should definitely be carried out by a qualified professional.
(iii) Strictly speaking, AS 2870 is a legally binding Deemed-to-Satisfy provision, as it is listed under the Deemed-to-Satisfy Provisions section of the NCC. However, since it also includes guidance for design by engineering calculations, it is more accurate to say that AS 2870 is legally binding and provides Deemed-to-Satisfy provisions.
CONCLUSIONS:
(i) AS 2870 is legally binding and provides Deemed-to-Satisfy provisions.
(ii) In case of conflicting information between NCC and AS 2870, the one with the more conservative values should be used.
(iii) An expert is not allowed to override a Deemed-to-Satisfy provision.
(iv) An engineer can apply a Performance Solution and use different values than those given in AS 2870 and NCC. It should be carried out by a qualified professional.
Reasoning Chain Demonstrating that AS 2870 is Legally Binding and Providing Deemed-to-Satisfy Provisions:
Quote 1-) Document: Western Australia Building Act 2011 Building Regulations 2012
Building Regulations 2012 - [04-j0-01].pdf
“Building Code means the Building Code of Australia which is Volumes One and Two, as amended from time to time, of the National Construction Code series published by, or on behalf of, the Australian Building Codes Board”
Quote 2-) Document: NCC 2019-A1 – Part A2
“A2.0 Compliance
Compliance with the NCC is achieved by complying with—
(1) the Governing Requirements of the NCC; and
(2) the Performance Requirements.”
Quote 3-) Document: NCC 2019-A1 – Part A2
“A2.2 Performance Solution
(1) A Performance Solution is achieved by demonstrating—
(a) compliance with all relevant Performance Requirements; or
(b) the solution is at least equivalent to the Deemed-to-Satisfy Provisions.”
Quote 4-) Document: NCC 2019-A1 – Part A2
“Part A2 Compliance with the NCC
Introduction to this Part
This Part explains the possible methods of demonstrating compliance with the NCC.”
Quote 5-) Document: NCC 2019-A1 – Part A2
“A2.3 Deemed-to-Satisfy Solution
(1) A solution that complies with the Deemed-to-Satisfy Provisions is deemed to have met the Performance Requirements.
(2) A Deemed-to-Satisfy Solution can show compliance with the Deemed-to-Satisfy Provisions through one or more of the following Assessment Methods:
(a) Evidence of suitability in accordance with Part A5 that shows the use of a material, product, plumbing and drainage product, form of construction or design meets a Deemed-to-Satisfy Provision.
(b) Expert Judgement.”
Quote 6-) Document: NCC 2019-A1 – Part A5
“A5.2 Evidence of suitability — Volumes One and Two
…
(2)Evidence to support that a calculation method complies with an ABCB protocol may be in the form of any one, or any combination of the following:
(a) A certificate from a professional engineer or other appropriately qualified person that—
(i) certifies that the calculation method complies with a relevant ABCB protocol; and
(ii) sets out the basis on which it is given and the extent to which relevant standards, specifications, rules, codes of practice and other publications have been relied upon.
(b) Another form of documentary evidence that correctly describes how the calculation method complies with a relevant ABCB protocol.”
Quote 7-) Document: NCC 2019-A1 – Part H1
“Deemed-to-Satisfy Provisions
H1D4 Footings and slabs
(1)Performance Requirement H1P1 is satisfied for the design and construction of footings and slabs if they comply with either (a) or (b):
(a) One of the following:
AS 2870.
AS 3600.
(b) Subject to (2), Section 4 of the ABCB Housing Provisions.”
DISCUSSION:
(i) Interestingly, the NCC tables under H1P1 (Quote 7) do not reference their own tables as Deemed-to-Satisfy provisions. However, Quote 2 states: “Compliance with the NCC is achieved by complying with (1) the Governing Requirements of the NCC; and (2) the Performance Requirements.”
So, what happens if there are discrepancies between the tables in AS 2870 and those in the NCC? For example, the stiffened raft height on a Class S site for articulated full masonry is listed as 500 mm in AS 2870 (Figure 3.1), while 400 mm is given in the NCC (Table 3.2.5.4b).
If we refer to the note at the beginning of Part 3.2.5 Footing and Slab Construction, it states: “The footings included in this Part reflect the requirements of AS 2870.” This clearly indicates that the NCC tables are derived from AS 2870. Therefore, in the event of a conflict, the original reference, AS 2870, should take precedence.
On the other hand, if for the cases if NCC more conservative than AS 2870 and since NCC is also legally binding NCC values should be used. This is the case for slab reinforcements.
(ii) Can an expert override a Deemed-to-Satisfy provision? According to NCC A2.3(2)(b) (Quote 5), an expert can demonstrate that a solution meets a Deemed-to-Satisfy provision using expert judgement. However, it is important to distinguish that while an expert can demonstrate compliance with a Deemed-to-Satisfy provision using alternative methods, they cannot override or change the provisions themselves.
To use footing heights smaller than those given in AS 2870, one must adopt a Performance Solution and this doesn’t have to be done by an expert. But it should definitely be carried out by a qualified professional.
(iii) Strictly speaking, AS 2870 is a legally binding Deemed-to-Satisfy provision, as it is listed under the Deemed-to-Satisfy Provisions section of the NCC. However, since it also includes guidance for design by engineering calculations, it is more accurate to say that AS 2870 is legally binding and provides Deemed-to-Satisfy provisions.
CONCLUSIONS:
(i) AS 2870 is legally binding and provides Deemed-to-Satisfy provisions.
(ii) In case of conflicting information between NCC and AS 2870, the one with the more conservative values should be used.
(iii) An expert is not allowed to override a Deemed-to-Satisfy provision.
(iv) An engineer can apply a Performance Solution and use different values than those given in AS 2870 and NCC. It should be carried out by a qualified professional.
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- Thread starter
- #20
Thank you for the info for the background argument; it is very helpful.
Let’s avoid being in that position. I will use the one provides more conservative values either AS 2870 or NCC because both of them are legally binding. If I decide to use smaller footing heights, I will need a reliable geotechnical report and solid, well supported calculations and a performance solution. To be honest, this is unlikely to be required for a typical residential design.
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