Is engineer's involvement required where the code states "unless calculation are provided" or "capacities are shown"

[sunyaer]

These are from Ontario building code Division B part 9:
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9.23.9.9. Cantilevered Floor Joists
(1) Floor joists supporting roof loads shall not be cantilevered more than 400 mm beyond their supports where 38 mm
by 184 mm joists are used and not more than 600 mm beyond their supports where 38 mm by 235 mm or larger joists are
used.
(2) The cantilevered portions referred to in Sentence (1) shall not support floor loads from other storeys unless
calculations are provided to show that the design resistances of the cantilevered joists are not exceeded
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9.17.3. Steel Columns
9.17.3.1. Size and Thickness
(1) Except as permitted by Sentence (2), steel pipe columns shall have an outside diameter of not less than 73 mm and a
wall thickness of not less than 4.76 mm.
(2) Columns of sizes other than as specified in Sentence (1) are permitted to be used where the loadbearing capacities
are shown to be adequate.
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Question:

Is engineer's involvement required to meet 9.23.9.9.(2) or 9.17.3.1.(2), or a designer who is qualified to design part 9 building is permitted to do the calculation?

 

[Mark K]

From a practical perspective it way be appropriate to hire an engineer. Does the individual "qualified" to design part 9 buildings have the engineering knowledge to perform the calculations?

 

[bill1952]

I agree with Mark . If you are not sticking to the prescriptive requirements, you need a registered design professional. I'm sure that many builders have done the calculations and building officials have accepted the design. Just can't count on it.

 

[tmurray]

The short answer is no. If the intention of the code was to refer the design process to a registered design professional, it would not include these clauses as we can always design components of the building to Part 4.

The question is would the AHJ accept something calculated by anyone but an engineer?

 

[tmurray]

From a practical perspective it way be appropriate to hire an engineer. Does the individual "qualified" to design part 9 buildings have the engineering knowledge to perform the calculations?

The way the Canadian code is structured, Part 9 is a prescriptive option, but always allows the builder to defer to Part 4, which would involve an engineer. Because the authors included this language specifically on these clauses, I would have to come to the conclusion that the code intended to include an option that these calculations to be completed by someone other than an engineer.

However, in practice I've only seen these types of calculations coming from engineers.

Not saying it is a good idea. This is just what the code says.

 

[Mark K]

If we recognize that only engineers have the knowledge to prepare these calculations, does it not follow that the building department individual checking these calculations should have this knowledge.

 

[tmurray]

If we recognize that only engineers have the knowledge to prepare these calculations, does it not follow that the building department individual checking these calculations should have this knowledge.

Well, this is a standard of care question that is answerable through case law. To summarize everything, and to give everyone's favorite answer: it depends. Ultimately it relies on the size of the jurisdiction, how often it would be expected to encounter something along these lines, and the ultimate risk to life safety.

The issue is that if we believe an engineer or architect is required to perform reviews, I now need one for structural, fire and life safety, plumbing, electrical, geotechnical....and my jurisdiction is now bankrupt.

It has been accepted that smaller jurisdictions can largely rely on registered design professionals for the design and inspection process.
It has also been accepted that jurisdictions can largely rely on registered design professionals for the design and inspection process for rare projects (think of a medium size jurisdiction getting a once in a lifetime development).
Where these situations are not true, jurisdictions would be expected to staff up engineers based on a life-safety risk associated with each discipline.

Ultimately, our court system has attempted to balance to advantage of the inspection regime with the costs to society. If it costs too much to perform the service, the jurisdictions will simply not provide the service and society does not receive any benefit. We've accepted that some benefit is better than none, avoiding the "nirvana" logical fallacy.

To directly answer your question, yes. It would be an expectation (and is actually the case in my direct experience) in Canada that larger jurisdictions would have engineers on staff capable of reviewing structural design, among other disciplines.

 

[Mark K]

If this is a standard of care issue I do not see why it should be different for small jurisdictions. Is a small design firm held to a lower standard than a large firm?

The critical point is that the individual who performs the review or who supervises the individual performing the review needs to be qualified.

Some jurisdictions have arrangements with firms that can perform reviews on a contract basis. Thus they only pay for what they need.

 

[tmurray]

If this is a standard of care issue I do not see why it should be different for small jurisdictions. Is a small design firm held to a lower standard than a large firm?

The critical point is that the individual who performs the review or who supervises the individual performing the review needs to be qualified.

Some jurisdictions have arrangements with firms that can perform reviews on a contract basis. Thus they only pay for what they need.

Standard of care in this context is part of the Anns test. The first part of the Anns test is whether a duty of care existed (i.e.: should the individual have had the injured party in mind when they undertook their action). The standard of care is if the agency limited their standard of care based on a bonafide restriction of resources (typically money). Ultimately, this is used because the duty of care is so wide, building inspection departments would be found at fault for almost any violation. The standard of care is to allow the jurisdiction to limit it's review and inspection services at a reasonable level. Because building officials in Canada do not benefit from any statutory immunities, without such a test one could easily see how quickly a building official would become what the court calls an insurer of construction, being liable for all construction errors.

Ultimately this is all settled law here in Canada, having been ruled on by our supreme court.

 

[Mark K]

While the specifics vary among the states in general government employees and governmental entities have immunity when they perform their job.

I suggest that in the US what standard of care would not be used in the context of the building department.

 

[Paul Sweet]

Manufacturer's load tables are usually prepared by an engineer. They just might not be registered in the same state (or province) as the project.

 

[sunyaer]

Manufacturer's load tables are usually prepared by an engineer. They just might not be registered in the same state (or province) as the project.

Unless the engineer stamps the drawing for the project, manufactuer's load tables are for reference ONLY.

 

[Inspector Gadget]

My view is that as soon as "unless calculations" clauses come into play, you're into an engineer's opinion.

I always work backward from "what am I gonna tell the judge?"
I may be able to look at a 4' cantilevered deck constructed of PT 16' 2x10's at 16" OC, all nailed and glued to interior joists and say, "gosh, I have a gut feeling that will work," but a court is not going to accept a gut feeling. Neither will our insurance company.

On the other hand, take a deck with 2x10 PT joists, 16" OC cantilevered 16" past a beam. I can look a judge in the eye and state for the record, "I approved that because it met the requirement of NBC clause 9.23.9.9(1)."

Part 9 or Part 4. Book or engineer. It's pretty clear-cut, IMHO.

 

[sunyaer]

My view is that as soon as "unless calculations" clauses come into play, you're into an engineer's opinion.

I always work backward from "what am I gonna tell the judge?"
I may be able to look at a 4' cantilevered deck constructed of PT 16' 2x10's at 16" OC, all nailed and glued to interior joists and say, "gosh, I have a gut feeling that will work," but a court is not going to accept a gut feeling. Neither will our insurance company.

On the other hand, take a deck with 2x10 PT joists, 16" OC cantilevered 16" past a beam. I can look a judge in the eye and state for the record, "I approved that because it met the requirement of NBC clause 9.23.9.9(1)."

Part 9 or Part 4. Book or engineer. It's pretty clear-cut, IMHO.

4' cantilevered is huge different from cantilevered 16" past a beam, isn't it?

 

[Inspector Gadget]

4' cantilevered is huge different from cantilevered 16" past a beam, isn't it?

Yes. However, I have seen exactly this on a jobsite, so it serves as a good example. Eng signed off on it. Would have ordered it removed otherwise.

 

[sunyaer]

Yes. However, I have seen exactly this on a jobsite, so it serves as a good example. Eng signed off on it. Would have ordered it removed otherwise.

The code and legislations do not work the way that "you" saw "exactly this on a jobsite". Even for the same enginner, "you" can not say I used it on a previous project and I can use it everwhere. Once the framing and loading conditions, you shall verify.

This is from OBC regarding cantilevered joist for reference:
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9.23.9.9. Cantilevered Floor Joists
(1) Floor joists supporting roof loads shall not be cantilevered more than 400 mm beyond their supports where 38 mm
by 184 mm joists are used and not more than 600 mm beyond their supports where 38 mm by 235 mm or larger joists are
used.
(2) The cantilevered portions referred to in Sentence (1) shall not support floor loads from other storeys unless
calculations are provided to show that the design resistances of the cantilevered joists are not exceeded.
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[sunyaer]

Typos: "and I can use it everywhere. Once the framing and loading conditions changed, you shall verify.

 

[Inspector Gadget]

The code and legislations do not work the way that "you" saw "exactly this on a jobsite". Even for the same enginner, "you" can not say I used it on a previous project and I can use it everwhere. Once the framing and loading conditions, you shall verify.

You seem to have totally misunderstood what I was stating.

Allow me to rephrase.
Contractor wanted a four-foot cantilever for a deck. I observed this. It was constructed contrary to approved plans. The contractor was provided three paths to compliance:
1) reduce the cantilever to acceptable part 9 requirements;
2) provide documents from a structural engineer stating the construction was acceptable under part 4
3) remove the construction.

 

[sunyaer]

...

Allow me to rephrase.
Contractor wanted a four-foot cantilever for a deck. I observed this. It was constructed contrary to approved plans. The contractor was provided three paths to compliance:
1) reduce the cantilever to acceptable part 9 requirements;
2) provide documents from a structural engineer stating the construction was acceptable under part 4
3) remove the construction.

This sounds correct.