Running conduit below a footing

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Desert Spark

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Hello all, new member and have gotten a lot info from the forum so Thank you. Just wanted to get some input on a current situation I’m dealing with. I’m running some underground for parking lot lighting and am meeting some obstacles, I need to cross two footings that will be supporting two small walls that follow a handicap ramp down to an existing sidewalk. The existing sidewalk and roadway limit my ability to trench from one pole light to another. The footings/walls will be poured soon and I’m wondering if I can run sch40 pvc the length of the footing trench, about 30’ to get to the next pole base. I’m concerned about settlement and all and am trying to figure out if this is a viable option or if I need to try and figure something out. I did a rough drawing, hopefully will make things more clear. Just wanted input from the forum as up until know I haven’t considered something like this. Thanks in advance for any insight.
Having trouble uploading images from phone. Will try soon from my computer.
 
I don't believe PVC is an issue running in the footing. I do know that plumbers have to sleeve their pipe with a larger pipe when going under a footing but I have never heard that about electrical conduit
 
Below the footing is just sitting on the earth so it shouldn't be an issue, in the footing someone might argue that it changes the integrity of the footing but even that would be a stretch.
 
Desert Spark said:
Hello all, new member and have gotten a lot info from the forum so Thank you. Just wanted to get some input on a current situation I’m dealing with. I’m running some underground for parking lot lighting and am meeting some obstacles, I need to cross two footings that will be supporting two small walls that follow a handicap ramp down to an existing sidewalk. The existing sidewalk and roadway limit my ability to trench from one pole light to another. The footings/walls will be poured soon and I’m wondering if I can run sch40 pvc the length of the footing trench, about 30’ to get to the next pole base. I’m concerned about settlement and all and am trying to figure out if this is a viable option or if I need to try and figure something out. I did a rough drawing, hopefully will make things more clear. Just wanted input from the forum as up until know I haven’t considered something like this. Thanks in advance for any insight.
Having trouble uploading images from phone. Will try soon from my computer.
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well, the only person who will have a problem with it is your inspector.

worse comes to worse, spin three lenghths or GRC togeather, throw it in
the ground, use FA's on each end to convert to pvc, and move on.
 
Dennis Alwon said:
I don't believe PVC is an issue running in the footing. I do know that plumbers have to sleeve their pipe with a larger pipe when going under a footing but I have never heard that about electrical conduit
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i've had to sleeve stuff as well. i just cut up a 4" pvc into 2' nipples, and toss them across the footing taped up before pouring,
if i have to run afterwards. if i'm running at the time, i toss it over the pipe, and duct tape it to keep a void.
 
Footing is supposed to be deep enough to be below maximum frost depth for the area as well as deep enough to be into undisturbed soil or at least on good mechanically compacted soil if fill has been brought in. This all to prevent settling or frost heave. If you have settling or frost heave because the footing wasn't done correctly your conduit for lot lighting will be of the least concern for the building owner when this is discovered.
 
Just ran into that with a 2in pvc.. They just wanted it wrapped with Styrofoam through the footing to it can move on it's own. But yes, the AHJ makes the final call.
 
Andy Delle said:
Just ran into that with a 2in pvc.. They just wanted it wrapped with Styrofoam through the footing to it can move on it's own. But yes, the AHJ makes the final call.
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My question is where is it going to go?

Temp is probably consistent enough that expansion isn't too much of an issue.

If settling is a potential issue, that little bit of styrofoam isn't going to save anything.
 
Wait for the footer to be placed, then put the conduit on top of the footer. That way, the conduit will be buried in soil, not in concrete. If you put the conduit in the trench before the footer's placed, there will be a 2.4-inch hole (more at the couplings) where the structural engineer planned on having concrete.

Or tell the structural engineer what you want to do and request a suggestion.
 
drcampbell said:
Wait for the footer to be placed, then put the conduit on top of the footer. That way, the conduit will be buried in soil, not in concrete. If you put the conduit in the trench before the footer's placed, there will be a 2.4-inch hole (more at the couplings) where the structural engineer planned on having concrete.

Or tell the structural engineer what you want to do and request a suggestion.
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For most smaller structures that footing has no problem bridging over a 2.4 inch void, or even bridging over a shovel width section that later was dug out to place a water, sewer, or electric line under an existing footing. Want to do that on a high rise or other large structure or something with unique load bearing characteristics? Maybe not a bad idea to consult the structural engineer. In those instances they had better already have plans on how you are to install what you need to install.
 
I go through a fair amount of footings.

Standard procedure for us is to sleeve it in something larger. But not so large the concrete contractor or GC question the integrity of the footing.

I don't even know if there'd be an issue without the sleeve, but it makes me feel warm and fuzzy when I sleeve it, so I'll continue to do so....
 
kwired said:
My question is where is it going to go?

Temp is probably consistent enough that expansion isn't too much of an issue.

If settling is a potential issue, that little bit of styrofoam isn't going to save anything.
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This is Los Angeles. Earthquakes, shear? They are real big on shear out here. All kinds of requirements the rest of the country doesn't have to genrally deal with.
 
Andy Delle said:
This is Los Angeles. Earthquakes, shear? They are real big on shear out here. All kinds of requirements the rest of the country doesn't have to genrally deal with.
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Ok good point. But I know nothing about footing design in such a place either. Get enough movement in that footing and an electrical conduit through that footing may be low on of my list of concerns at that time.

Here a footing is not designed to have any movement at all for the most part, I don't know how many thousandths of an inch might be considered acceptable though.
 
I was here in 1994 for the Northridge quake. Actually I have been here since 1983 after growing up in the north east and have felt many prior quakes. I too said "what's the big deal" People that went through the 1971 Sylmar quake told me I just don't get it.

Well I get it now. I learned what is really meant by "the finger of God". Those footings can move quite a bit more than a few thousandths of an inch. Try several inches to over a foot!
 
Andy Delle said:
I was here in 1994 for the Northridge quake. Actually I have been here since 1983 after growing up in the north east and have felt many prior quakes. I too said "what's the big deal" People that went through the 1971 Sylmar quake told me I just don't get it.

Well I get it now. I learned what is really meant by "the finger of God". Those footings can move quite a bit more than a few thousandths of an inch. Try several inches to over a foot!
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Are footings designed to move several inches to over a foot without the need to redo things after that happens where you are? thousandths of an inch may be a little exaggeration on my part for what to expect here, but anything over maybe 1/4 inch of movement would be considered a lot of movement here I would think.
 
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