Foundation depth

[Yankee Chronicler]

Frost depth for this entire state is set by the codes at 42 inches. If someone submits a set of drawings that shows the top of footings at 42 inches below grade, I'll approve it because it's better than code. But everything I see has the bottom of footing at 42 inches, which I regard as complying and which I have always approved.

You can always do better than what the code requires, but in the case of concrete that's buried beneath the building I consider it wasted money. Nobody ever sees it, nobody ever gets any benefit or enjoyment out of it -- so why do it?

 

[steveray]

A gawdawful way to measure something when the metric system exists and solves all those fractional foulups with a nice decimal solution.

Don’t get your metric system on me…Makes me itch and I’m still looking for the 10mm socket…

 

[steveray]

Shirley Prudence would demand satisfaction of the reason behind the intent. If such minute extensions were enough, the code should probably just ask that the footing start at the frost line and rise from there.

Have Faith and Hope that common sense prevails…Les not forget that Vladimir could be teaching a class and just wants the technically correct answer. Shirley no one would split hairs to the level of 42 vs. 42.00001 inches in the real world.

 

[Inspector Gadget]

Have Faith and Hope that common sense prevails…Les not forget that Vladimir could be teaching a class and just wants the technically correct answer. Shirley no one would split hairs to the level of 42 vs. 42.00001 inches in the real world.

This leads to an interesting question that has merit in the real world. At what point is a deviation from code a deviation that one enforces?
Let's say ... a guard. I think the US Codes and Canadian Codes are unified.... so commercial guards are 107cm/42 inches.
Is it a code violation if the guard is 41 7/8"? 41 3/4"? 41 1/2"?
Would it be written up by all of us the same way? If not, why?

 

[steveray]

This leads to an interesting question that has merit in the real world. At what point is a deviation from code a deviation that one enforces?
Let's say ... a guard. I think the US Codes and Canadian Codes are unified.... so commercial guards are 107cm/42 inches.
Is it a code violation if the guard is 41 7/8"? 41 3/4"? 41 1/2"?
Would it be written up by all of us the same way? If not, why?

In my day to day....a 42" guard has infinite construction tolerance.. Above 42"... A range is a range and max and min are max and min.....That being said, I don't pull out a tape measure all that often these days...

 

[Yikes]

You can always do better than what the code requires, but in the case of concrete that's buried beneath the building I consider it wasted money. Nobody ever sees it, nobody ever gets any benefit or enjoyment out of it -- so why do it?

Reminds me of the aphorisms I most appreciate about value engineering:

• Any idiot can build a bridge that stands, but it takes a great engineer to build a bridge that barely stands.

 

[ICE]

Any idiot can build a bridge that stands, but it takes a great engineer to build a bridge that barely stands.

You have mixed up the two.

 

[Yankee Chronicler]

• Any idiot can build a bridge that stands, but it takes a great engineer to build a bridge that barely stands.

You have mixed up the two.

Not at all. It's easy to engineer something and decide you're not sure, so you'll just add an extra 10% or an extra 25% "just to be safe." It's the experts who figure the design to a gnat's eyelash, so it just meets the code without using an ounce of extra material or costing a penny more than the bare minimum that's required.

 

[ICE]

Not at all. It's easy to engineer something and decide you're not sure, so you'll just add an extra 10% or an extra 25% "just to be safe." It's the experts who figure the design to a gnat's eyelash, so it just meets the code without using an ounce of extra material or costing a penny more than the bare minimum that's required.

They can be cut by their own knife’s edge.

 

[Yankee Chronicler]

As a former State Building Inspector used to remind us when we had live in-service training classes, 'The code is the least you can accept and the most you can require." It's more difficult to design right to the limits than it is to just throw a little extra in "to be safe." Code compliant is code compliant.

 

[bill1952]

Not at all. It's easy to engineer something and decide you're not sure, so you'll just add an extra 10% or an extra 25% "just to be safe." It's the experts who figure the design to a gnat's eyelash, so it just meets the code without using an ounce of extra material or costing a penny more than the bare minimum that's required.

Brinkmanship.

 

[Yikes]

They can be cut by their own knife’s edge.

Once you get past prescriptive code, all engineering is a determination of where the knife's edge is located, and a cost/benefit analysis regarding safety risk.
I know I've shared this several times before, but it bears repeating:

 

[bill1952]

Once you get past prescriptive code, all engineering is a determination of where the knife's edge is located, and a cost/benefit analysis regarding safety risk.
I know I've shared this several times before, but it bears repeating:

Where can I get the prescriptive code for bridges? Bills Bridge Builders LLC. Who needs those engineers.

 

[mark handler]

1809.5 Frost Protection
Except where otherwise protected from frost, foundations and other permanent supports of buildings and structures shall be protected from frost by one or more of the following methods:
1. Extending below the frost line of the locality

 

[Yankee Chronicler]

Brinkmanship.

Using the literal definition of "brinkmanship" -- taking something to the brink -- that's correct. And yet it can be argued that an engineer who DOESN'T do that isn't being responsible to his/her clients. After all, the codes are based on accepted engineering standards, and accepted engineering standard supposedly have adequate safety factors built into them. And the building codes are supposed to establish a reasonable balance between safety and economy/affordability.

Example: When I graduated from architecture school, I landed a job as a drafter in a firm that did a lot of factories. On the very first project I was assigned to draw up, the client was a corporation that had recently built essentially the same building we were doing but in another state. The structural engineer my boss used on the project showed diagonal bracing members in the plane of the roof structure. The client's representative objected that they had not done that in the other building, and he didn't want to spend money on something that wasn't necessary.

The boss called the engineer in. The engineer admitted that the roof deck welded to the structure provided all the lateral bracing needed in the roof plane, but he had added the bracing members because he thought it was "better."

The client was not impressed. He said they weren't buying "better," they were buying code compliance. So the boss had to give the engineer a choice -- either remove the extra bracing members, or be removed from the project. The engineer grumbled, but he removed the bracing members. The building was built, and 50-plus years later, having been through a couple of hurricanes, it's still standing.

It's easy to add an extra X percent when it's not your money you're spending, but is it responsible? As long as a design meets code, calling for more than what the code requires is (IMHO) irresponsible unless the client knows you're going beyond the code and either agrees with that approach or has specifically requested that approach.

 

[redeyedfly]

I dont want to argue. This is a discussion board, and that little nuance is at the heart of my question

There's no nuance here. The design frost depth is what is stated in the code. You need to bear below it. This isn't rocket science.

Sorry you had a nonsense take and have wasted your client's money designing foundations that are 10-12" deeper than they need to be for any rational or code reason.

There are loads of gray areas in the code that bear discussion, this is not one of them.

 

[Yikes]

They can be cut by their own knife’s edge.

To your point, here’s China a few hours ago, on the other side of the knife’s edge.
(In fairness, preliminary reports indicate it wasn’t the bridge itself that was unstable, but rather the the mountain on which it was bearing was unstable.

 

[ICE]

When the dust settles they will have it back up in a month or two. Only half of it went down.

 

[Yankee Chronicler]

To your point, here’s China a few hours ago, on the other side of the knife’s edge.
(In fairness, preliminary reports indicate it wasn’t the bridge itself that was unstable, but rather the the mountain on which it was bearing was unstable.

The IBC requires a geotechnical report as part of the required documentation for a new building. It's mind-blowing how many owners and architects argue that they shouldn't have to do that.

 

[Yankee Chronicler]

To your point, here’s China a few hours ago, on the other side of the knife’s edge.
(In fairness, preliminary reports indicate it wasn’t the bridge itself that was unstable, but rather the the mountain on which it was bearing was unstable.

If you look at 4:08 of the video, you can see what appears to be a couple of railroad tunnels on the far side of the river. My guess is that if there was a railroad there, it's now in the past tense.

 

[bill1952]

calling for more than what the code requires is (IMHO) irresponsible

Code is not always right. Code compliance is a necessary condition but often not sufficient. I think of structured floors that meet code but.deflect so much they are discomforting. Minimum widths for comfortable circulation. In my work - designing assembly seating - code minimums guarantee complaints. I could go on but designing to code minimums is not good design.

 

[Yankee Chronicler]

Codes are a consensus about what a group has agreed represents a minimum standard for an acceptable level of safety. That's ALL codes are. Nobody ever said designing to code minimums will result in great architecture. An owner (and an owner's designers) always has the option to exceed code. My point is that, absent an understanding that the owner wants or agrees to exceed code minimums, it is irresponsible for a designer to exceed code requirements just because it's easier or because he/she (the designer) isn't comfortable in their ability to design to the razor's edge of compliance. That's spending the owner's money on something the owner may not want his/her money spent on.

 

[bill1952]

minimum standard for an acceptable level of safety.

First the IBC says "reasonable" level of safety. Relying on AI: "Reasonable" implies something is fair, sensible, and based on good judgment, while "acceptable" means it meets minimum requirements or is simply satisfactory. Reasonable is a higher standard that suggests appropriateness and rationality under the circumstances, whereas acceptable can be just good enough or barely adequate."

Second, that says nothing about function. I can design a building that complies with all codes but is totally disfunctional and does not meet the needs of the owner. Buildings are about more than being safe.

Third, and owner selected me for my expertise and understanding of their needs, which beside cost and code compliance, involve function and comfort and perhaps greater safety than the code minimum. From energy efficiency to stair geometry to structural strength to aesthetics, code minimums are rarely the best design.

 

[ICE]

There is a half of a span that is now cantilevered. That presents a hazard that will be difficult to overcome without bring the rest of the construction down.