The infamous and elusive UFER

[infinity]

Short version of what I said, thanks.

Yes you did I was simply agreeing with what you said.

 

[jaggedben]

Note that even this local amendment does not require the creation of a CEE where the design calls for a membrane between the foundation/footing and the substrate. It does not matter one way or the other is a membrane is installed only under the slab portion of the foundation. ...

You read it differently than me, then. I read it as requiring a CEE to be installed, full stop. Thus, if a membrane would disqualify a CEE, then this section prohibits the membrane. I don't know from experience if the question has actually come up in SF.

 

[zbang]

That interpretation may be at odds with building codes that would require a barrier as well as local "good practice" designs.

Here's a part of the Calif. building code

R406.2 Concrete and Masonry Foundation Waterproofing
In areas where a high water table or other severe soil-water conditions are known to exist, exterior foundation walls that retain earth and enclose interior spaces and floors below grade shall be waterproofed from the higher of (a) the top of the footing or (b) 6 inches (152 mm) below the top of the basement floor, to the finished grade.

And from the SF amendments-
1805A.2.1 Floors
Dampproofing materials for floors shall be installed between the floor and the base course required by Section 1805A.4.1, except where a separate floor is provided above a concrete slab.
Where installed beneath the slab, dampproofing shall consist of not less than 6-mil (0.006 inch; 0.152 mm) polyethylene with joints lapped not less than 6 inches (152 mm), or other approved methods or materials. [...]

(I'm not going to chase this further.)

 

[jaggedben]

I don't see a conflict, as nothing in those citations requires a barrier beneath a footing. Of course if there was a conflict, that would be ... a conflict, and something would have to win out.

 

[GoldDigger]

You read it differently than me, then. I read it as requiring a CEE to be installed, full stop. Thus, if a membrane would disqualify a CEE, then this section prohibits the membrane. I don't know from experience if the question has actually come up in SF.

"... when a new or replacement foundation or footing with a perimeter length of 6.0 m (20 ft.) or more is installed in direct contact with the earth."

That sure looks like an exception to me.

 

[jaggedben]

"... when a new or replacement foundation or footing with a perimeter length of 6.0 m (20 ft.) or more is installed in direct contact with the earth."

That sure looks like an exception to me.

I see. Maybe so.

 

[wwhitney]

"... when a new or replacement foundation or footing with a perimeter length of 6.0 m (20 ft.) or more is installed in direct contact with the earth."

Right, but that only applies to existing buildings; the language requiring a CEE for new buildings has no such exception.

So for new building, if you are required to create a CEE, but you want or need a vapor barrier under your footing, then you just need to cast a sufficiently large extra chunk of concrete directly against the earth, alongside your footing but outside your vapor barrier. No conflict.

Cheers, Wayne

 

[jaggedben]

Right, but that only applies to existing buildings; the language requiring a CEE for new buildings has no such exception.

So for new building, if you are required to create a CEE, but you want or need a vapor barrier under your footing, then you just need to cast a sufficiently large extra chunk of concrete directly against the earth, alongside your footing but outside your vapor barrier. No conflict.

Cheers, Wayne

[Deleted previous comment.]

That's really weird how they wrote it, now I read carefully. Unless it's a punctuation error. But very par for the course with SF DBI and code writing in general.

Take out the comma and it makes more sense.

 

[Seven-Delta-FortyOne]

I pour a lot of concrete foundations.

On a stem wall with wood frame, or a slab inside, like in a lot of shop type buildings, the CEE is there and used.

On virtually all slab on grade, where the building is going to be heated, the vapor barrier is required, and here in California, the latest Code requires it to be a 10 mil. It is wrapped under the footing, as that is the only way to run it.

On every one that I have poured, due to the vapor barrier being present, the CEE is determined “not to be present” by the AHJ, and they want the standard two ground rods.

 

[Elect117]

Pardon my ignorance here, but shouldn't that detail be present on the plans that are run through plan check?

I feel like that can be planned/accounted for prior to start of construction.

 

[Npstewart]

ALL, OP Here.

Just a little update. They went ahead and installed a UFER Ground because they have to pour concrete in an additional area of the home.

HOWEVER, the inspector is asking for a TEST on the UFER to prove there is MORE THAN 25 ohms. Does this make sense? There is only 1 area in the NEC that requires a ground test, but that test requires 25 Ohms or LESS and off memory, that only applies to ground rods to avoid a supplemental ground.

Why would someone ask for a test showing MORE THAN 25 Ohms for a UFER?

 

[Joe.B]

Why would someone ask for a test showing MORE THAN 25 Ohms for a UFER?

Because they're being an idiot?

 

[rc/retired]

ALL, OP Here.

Just a little update. They went ahead and installed a UFER Ground because they have to pour concrete in an additional area of the home.

HOWEVER, the inspector is asking for a TEST on the UFER to prove there is MORE THAN 25 ohms. Does this make sense? There is only 1 area in the NEC that requires a ground test, but that test requires 25 Ohms or LESS and off memory, that only applies to ground rods to avoid a supplemental ground.

Why would someone ask for a test showing MORE THAN 25 Ohms for a UFER?

Your inspector is way off on this! A CEE Does not require a 25 Ohms OR LESS resistance test.
You are correct with the ground rod requirement but not more than 2 ground rods are required regardless of how many Ohms there are.
Good luck!

Ron

 

[Seven-Delta-FortyOne]

Because he has numbers and Codes rattling around in his head like cue balls in a hard-sided suitcase, and he can’t make heads or tails of it all, so he spits out randomness like the little machine that ejects balls at the lottery drawing? Just my guess.

 

[Npstewart]

Because he has numbers and Codes rattling around in his head like cue balls in a hard-sided suitcase, and he can’t make heads or tails of it all, so he spits out randomness like the little machine that ejects balls at the lottery drawing? Just my guess.

What a coincidence. I had the IDENTICAL theory. LMAO

 

[roger]

Why would someone ask for a test showing MORE THAN 25 Ohms for a UFER?

Did he have a red nose and big black shoes on?

 

[Npstewart]

This is a screen shot of the email by the way. This is from the inspector.

 

[Npstewart]

Did he have a red nose and big black shoes on?

HA. Yes, and rides around on an undersized bicycle.

I just posted the email from the inspector..

 

[hornetd]

What if it’s slab on grade with a vapor barrier?


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I have never seen a slab on grade floor without the trenches for the footer at the edges. Is there such a thing as a slab on grade with no footer under the outside walls?

 

[hornetd]

I haven’t updated my profile in 15 years. Also, somehow made it to post #13 prior to a code citation being mentioned.

I spoke with the building official and he agreed. Half of his inspectors were fine with 2 rods and the other half weren’t. Not sure why this 1 house this 1 time was an issue, but it was.


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Perhaps it is because the inspector knows their J O B and sees their job as actually enforcing the NEC as written.

I recall one inspector, about 10 years ago, saying "Oh you missed the concrete encased electrode? Well that's OK I'll except a ground ring in it's place." I don't think that GC is likely to forget the CCE again. A 30 inch deep trench all the way around the building with bare #2 copper in every inch of it? I would think that would cost more than the GEC and the rebar clamp would have what with bringing the backhoe out to the site again. Maybe he should have had the concrete foreman dig the trench by hand. The CCE would never get forgotten again.

I have no sympathy with the apologists for careless work. A CCE, properly executed, is the cheapest and most effective electrode a home could have except in the areas served by water utilities that require copper pipe for the service lateral and connect it metallically to the water main. 1008 square miles of looped and gridded metal and metal reinforced concrete pipe make one hell of a Grounding Electrode.