AS 2870 vs NCC 1

[LiamJS]

There are discrepancies between AS 2870 and NCC for the footing heights provided in tables. Why is the reason?

 

[Euler07]

I think you would need to clarify some of the statements. Some of your conclusion contradicts the quotes from the NCC, or needs further clarification to support the conclusions.

(i) AS 2870 is legally binding and provides Deemed-to-Satisfy provisions.

What does "legally binding Deemed-to-Satisfy" mean? The deemed-to-satisfy options are not legally binding unless I'm missing something.

Only the performance requirements are mandatory. There are multiple ways of demonstrating compliance with the performance requirements, one of which is AS2870 in the deemed-to-satisfy provisions. This does not mean that AS2870 is the only method of demonstrating compliance.

(ii) In case of conflicting information between NCC and AS 2870, the one with the more conservative values should be used.

Is there a direct quote from the NCC that says this?

(iii) An expert is not allowed to override a Deemed-to-Satisfy provision.

Can you clarify what this means? An expert can show that a solution "is at least equivalent to the Deemed-to-Satisfy Provisions." The expert would not need to override anything.

 

[human909]

This general discussion is a really interesting discussing. Unfortunately most Australian engineers (myself included) have quite limited idea on how exactly the law applies to them and I doubt that most involved in the whole approval process have a good understanding either. It likely isn't until you get into the court room or in front of a disciplinary board that you start dealing with those who have a proper understanding.

In my (somewhat naive understanding), us engineers can get away with almost anything we want if we we can back it up from a performance perspective. Though when it comes to residential design, things are often so prescriptive that engineers could get trapped by a design that performs perfectly adequately for all relevant loads, but doesn't perform in the same manner as the prescribed design.

I do plenty of work where there exists no appropriate Australian standards or where the relevant structural standard has been withdrawn and not replaced. So I'm used to playing in the wild west of engineering. But in some ways it is easier as structural performance is what matters rather than following "THE" rule book.

 

[rowingengineer]

Lots of interesting statements, and so many different ways for you to be reviewed (in Qld, qbbc, rpeq, small claims, courts to name a few).

I do hope in Queensland that everyone who is designing footing for houses is using as2870 or a higher order analysis as referenced in the code, as the qbbc insurance starts here. In qld the building code is a seperate area to the qbcc code so is very grey area as to which one is more appropriate, so expert opinion will hold heavy sway, around expected performance.

Technically every builder should ensure that the engineer uses this standard, but I think you could argue that the engineer should know it is standard practice in Qld for class 1a buildings..... However since when do engineers make good lawyers.

 

[LiamJS]

I think you would need to clarify some of the statements. Some of your conclusion contradicts the quotes from the NCC, or needs further clarification to support the conclusions.

(i) AS 2870 is legally binding and provides Deemed-to-Satisfy provisions.

What does "legally binding Deemed-to-Satisfy" mean? The deemed-to-satisfy options are not legally binding unless I'm missing something.

Only the performance requirements are mandatory. There are multiple ways of demonstrating compliance with the performance requirements, one of which is AS2870 in the deemed-to-satisfy provisions. This does not mean that AS2870 is the only method of demonstrating compliance.

I didn't say "legally binding Deemed-to-Satisfy". Building act 2012 makes NCC legal document and NCC makes AS 2870 a legal document to satisfy Deemed-To-Comply-Provision. (There are other ways such as expert opinion but I am focused on Deemed-To-Comply and "AS 2870 vs NCC" here).

(ii) In case of conflicting information between NCC and AS 2870, the one with the more conservative values should be used.

Is there a direct quote from the NCC that says this?

No, kind of, this is why I am posting here. If you look at my Quote-2 above, here:

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.”

Performance requirements can be complied by Deemed-To-Satisfy Solution, so AS 2870. Hence, to comply with NCC we have to comply with (a) the Governing Requirements of the NCC; and (b) AS 2870 (If we choose to use Deemed-To-Satisfy provisions). What happens if they conflict? They shouldn't, this is the annoying part. However, they do. What will we do? This part is my interpretation. I say that we should comply with both of them.

(iii) An expert is not allowed to override a Deemed-to-Satisfy provision.

Can you clarify what this means? An expert can show that a solution "is at least equivalent to the Deemed-to-Satisfy Provisions." The expert would not need to override anything.

An expert can show that a solution "is at least equivalent to the Deemed-to-Satisfy Provisions." and that expert can also go below it but the only way to do this is to provide a performance solution. For example, an expert can do a performance solution and can use smaller depths for the footings than those given in AS 2870 as Deemed to Satisfy Solution.

However, that expert cannot say "I am an expert and feel that AS 2870 conditions are too much for this case and I will use smaller ones". No mate you have to use some engineering, please. Unfortunately, as I understand from the media release of WA Government, an expert doesn't have to provide any calculation for a performance solution if it is hard to do so! How about that expert does not provide any solution at all if it is hard to do so?!