Direct contact with the earth

[tkb]

250.52(A)(3) Concrete-Encased Electrode. An electrode encased by at least 50 mm (2 in.) of concrete, located within and near the bottom of a concrete foundation or footing that is in direct contact with the earth,........

When a vapor barrier is under the footing, the footing is not in direct contact with the earth.

How about when they dig out for the footing and then compact crushed stone for a base under the footing?
Is this in direct contact or do they mean virgin soil?
What if the footing is directly on ledge? Will it make a good concrete encased electrode?

[ August 02, 2005, 05:53 AM: Message edited by: tkb ]

 

[charlie tuna]

Re: Direct contact with the earth

tkb,
when you consider the actual function of the average driven ground rod will not clear a 15 amp breaker even if driven 50 feet down into the earth with 45 feet of it in contact with water, is the vapor barrier an issue? they say the concrete encased electrode is a better ground -- it doesn't have to be much to be better. considering that the reinforcement steel is tied throughout the foundation there is plenty of surface in contact with the soil!!! my $.02!

 

[physis]

Re: Direct contact with the earth

Earth isn't an insulator, plastic is. contact with earth is pretty vague but I would consider it to mean electrical contact and agregate to be near the same conductivity so my assumtion would be that rocks and plastic would be comletely different with regard to contact.

But is that how the code is written?

 

[tom baker]

Re: Direct contact with the earth

Just cut out the plastic for 20ft under the footing and you will be in conformance.

 

[be4jc]

Re: Direct contact with the earth

Can I ask why you put a moisture barrier under your footings? is this an adopted local ordinance because of high moisture content?
I have done Inspections on the Sacramento CA. River delta where elevation was below sea level and this was not required
B.E. Building Inspector II

 

[jimwalker]

Re: Direct contact with the earth

"Just cut out the plastic for 20ft under the footing and you will be in conformance."

fast way to flunk the slab inspection here.
Something to think about is the plastic is just under the footer.After it is poored and form taken away it will have a min.of 6 inches of dirt on the outside edge.
Is this really a good way to handle lightning ? Send it the footer and blow it up ?

 

[ryan_618]

Re: Direct contact with the earth

Everybody seems to glaze over the part that says footng or foundation. If the foundation gets backfilled, it seems like it would be in contact with the earth.

 

[jimwalker]

Re: Direct contact with the earth

exactly,i have never seen anyplace that allowed you to build on a slab just poored on top of the ground.They will always have some fill around them

 

[tom baker]

Re: Direct contact with the earth

In my area (Puget Sound) there is no frost depth and a footing is not required for a simple slab.

Just cut out the plastic for a twenty foot length at the footing and you will be compliant.

 

[jimwalker]

Re: Direct contact with the earth

Do they not worry about floods washing the dirt away from under it ?