# PVC in concrete slab



## Steve W (Dec 18, 2008)

Conduit must be Under no less than 2" concrete


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## aftershockews (Dec 22, 2012)

Look in 



> Table 300.5 Minimum Cover Requirements, 0 to 600 Volts, Nominal, Burial in Millimeters (Inches)


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## czars (Aug 20, 2008)

Thanks! I missed the note.


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## 220/221 (Sep 25, 2007)

What kind of conductors?

If Romex, be prepared to argue that the AB material under the slab isn't "earth".

Use UF or THWN and you will get no flak.


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## McClary’s Electrical (Feb 21, 2009)

Steve W said:


> Conduit must be Under no less than 2" concrete


Oh really?


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## hardworkingstiff (Jan 22, 2007)

czars said:


> I have a customer that wants several floor boxes installed in an existing concrete slab floor. I've never done this. I plan to cut a trench in the slab and run the conductors in PVC conduit and install metal Arlington Industries metal boxes. I can't find a code reference as to the required depth of the conduit. How deep must the conduit be installed??


If it were me, I'd look at a PVC floor box.


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## WantAndAble (Feb 19, 2015)

I would normally do core line in slab. But if you're going the pvc route I definitely think it makes more sense to just use pvc boxes.



> Conduit must be Under no less than 2" concrete


Now I'm Canadian and I know there are differences between NEC and CEC, but Ive done quite a bit of slab in Canada and buried core line and PVC of sizes ranging from 1/2" to 4" in 6 feet of Concrete. What is the difference between that and this? I'm curious. Where are you getting that rule? Is that NEC? Do you normally not use PVC in deep concrete work? If so, what do you use?


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## B-Nabs (Jun 4, 2014)

WantAndAble said:


> I would normally do core line in slab. But if you're going the pvc route I definitely think it makes more sense to just use pvc boxes.
> 
> 
> 
> Now I'm Canadian and I know there are differences between NEC and CEC, but Ive done quite a bit of slab in Canada and buried core line and PVC of sizes ranging from 1/2" to 4" in 6 feet of Concrete. What is the difference between that and this? I'm curious. Where are you getting that rule? Is that NEC? Do you normally not use PVC in deep concrete work? If so, what do you use?


The rule quoted says NO LESS THAN 2", so you could bury it in 6 feet of concrete all you want....


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## Southeast Power (Jan 18, 2009)

czars said:


> I have a customer that wants several floor boxes installed in an existing concrete slab floor. I've never done this. I plan to cut a trench in the slab and run the conductors in PVC conduit and install metal Arlington Industries metal boxes. I can't find a code reference as to the required depth of the conduit. How deep must the conduit be installed??


I don't know why this thread is bugging me so much but, you can embed PVC in concrete. I can't see why anyone would suggest that you need that much cover in an interior slab?
You don't get that much cover on a high rise slab.


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## Southeast Power (Jan 18, 2009)

czars said:


> I have a customer that wants several floor boxes installed in an existing concrete slab floor. I've never done this. I plan to cut a trench in the slab and run the conductors in PVC conduit and install metal Arlington Industries metal boxes. I can't find a code reference as to the required depth of the conduit. How deep must the conduit be installed??


Is there tile going over it?
I think the only limit would be on how the patch would react. It it will crack or look bad.


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## ampman (Apr 2, 2009)

Also check to see if the slab is prestressed with cables cut one of those and it s a bad day so I hear


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## Steve W (Dec 18, 2008)

Steve W said:


> Conduit must be Under no less than 2" concrete


Nevermind my mistake , under 2" is just considered outside of a building.


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## btharmy (Jan 17, 2009)

czars said:


> I have a customer that wants several floor boxes installed in an existing concrete slab floor. I've never done this. I plan to cut a trench in the slab and run the conductors in PVC conduit and install metal Arlington Industries metal boxes. I can't find a code reference as to the required depth of the conduit. How deep must the conduit be installed??


For power only, or do they want voice/data as well?


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## McClary’s Electrical (Feb 21, 2009)

B-Nabs said:


> The rule quoted says NO LESS THAN 2", so you could bury it in 6 feet of concrete all you want....


Oh really ?


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## B-Nabs (Jun 4, 2014)

mcclary's electrical said:


> Oh really ?



I sense sarcasm, but I'm not sure what you're getting at.


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## McClary’s Electrical (Feb 21, 2009)

czars said:


> I have a customer that wants several floor boxes installed in an existing concrete slab floor. I've never done this. I plan to cut a trench in the slab and run the conductors in PVC conduit and install metal Arlington Industries metal boxes. I can't find a code reference as to the required depth of the conduit. How deep must the conduit be installed??


It sounds like your inside the building so the answer is zero.


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## Southeast Power (Jan 18, 2009)

I'm having this situation right now.
The GC had a deal with the plumbers for all the cutting, the suck and tried to have the laborers chip it our for us and they cut a shallow V with a chipping hammer and have been at it for 2 days.
I'm going to rent a street saw, make the cuts and have them remove the concrete.
This is a first floor, slab on grade. The depth varies from 4" to 8" or more as they didn't grade out the space very well before the pour.
I want to stay just above the steel to avoid any problems with the owner.
The floor has #4 rebar and a mat. 
I'm thinking of going down 3" and looking for 2" of cover as the finished concrete floor will be exposed.
I have six floor boxes going in and 3 stub up about 7' away from the closest wall.
Question. In 3" overkill for an interior in slab cut and patch job?


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## Southeast Power (Jan 18, 2009)

I think the word "embedded" is used for indoor conditions.
I'm not so sure I can make much of a case for the installation with the word "embedded" being somewhat up to interpretation by the AHJ.


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## telsa (May 22, 2015)

*This is Standard Drill in California TI work.*

1) Chipping out the slot is not permitted: it weakens the slab too much -- and boy does it waste labor.

2) These saw-cuts are ALWAYS farmed out to spe******ts -- who will pop in on almost no notice. 

Does this forum have something against sub-contractors?!!!?

Non-spe******ts don't have a chance in H of competing with the experts -- starting with the fact that they not only cut the slab -- they haul away the chunks.

3) It's REQUIRED practice out here for wedge anchors/ rebar (glued in place) to be drilled into the sides of the slab cut after the underslab work is finished and inspected. 

Viscreen is laid down -- taped to seal -- and rebar then tied across the gap -- anchor to anchor -- for a re-pour.

&&&

The picture of the crew chipping away with electric hammers -- :no::laughing::no::laughing:


&&&&

As for the raceway:

School #1 is PVC with PVC "mud boxes" Carlon, Arlington, ... you name it ... every NEMA player is selling them. Unless the job is Cost-Plus, PVC is the way to go.

UF is simply not permitted by the AHJ -- and is a CRAZY economic design. ALL of the money was spent in the trench -- NOT the wire -- NOT the raceway.

&&&&&

A data-com run is now an automatic design feature... both ENT and PVC are popular for data-com. You'll see spec's of 1.25" min for PVC/ENT all the time. For a small job that's overkill. 1" should do fine.

The 'mud boxes' (trade slang for you) come with factory hubs up to 1 1/4" -- and also come with reducers -- as a kit. They don't come with an "activation" i.e. the final trim out is a SEPARATE purchase.

PVC is so popular BECAUSE it's cut flush to the concrete AFTER the pour -- giving you a PERFECT fit for the "activation"/ trim out.

Bring your knee pads -- gloves -- and your curse word thesaurus. This task is the perfect opportunity to bone up on new utterances.:laughing:


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## btharmy (Jan 17, 2009)

I just did this a couple weeks ago. Sub out the cut, removal and clean up. Lay in the PVC, level the box, drill and pin the trench and mix/pour the concrete. Started at 6:00am and was done before lunch.














Just make sure when finishing the concrete, better too low than too high. Floor guys will happily slap down some quick dry filler rather than grind down high spots.


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## Jmiester (Apr 8, 2015)

telsa said:


> 1) Chipping out the slot is not permitted: it weakens the slab too much -- and boy does it waste labor.
> 
> 2) These saw-cuts are ALWAYS farmed out to spe******ts -- who will pop in on almost no notice.
> 
> ...


And... Exhale


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## Southeast Power (Jan 18, 2009)

200' of cuts in about 100' of trench we opened, 
It took 16 man hours and a rented 14" walk behind saw.
Saw rental was $150.
I spent an hour removing about 1/3 of the concrete. The plumbers laborer is going to finish it today.
I excluded trenching in my agreement but couldn't wait for them.
Next time it will be included in my work and subbed out.


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## Southeast Power (Jan 18, 2009)

btharmy said:


> I just did this a couple weeks ago. Sub out the cut, removal and clean up. Lay in the PVC, level the box, drill and pin the trench and mix/pour the concrete. Started at 6:00am and was done before lunch.
> View attachment 56649
> View attachment 56657
> 
> ...


What method are you going to use to come out of that box?


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## hardworkingstiff (Jan 22, 2007)

jrannis said:


> Next time it will be included in my work and subbed out.


That's the ticket. The more you control, the more control you have.


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## btharmy (Jan 17, 2009)

jrannis said:


> What method are you going to use to come out of that box?


What you see is a blank. It is a multi compartment box. Hubbell I think. There are 2 1-1/4" conduits. 1 for voice/data, 1 for AV. The 3/4" is for power. It actually is offset down and 90 up into the bottom. All of the devices and jacks mount inside the box. The box has a cover with small access doors for cords to pass through. It is going under a conference table.


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## sbrn33 (Mar 15, 2007)

btharmy said:


> I just did this a couple weeks ago. Sub out the cut, removal and clean up. Lay in the PVC, level the box, drill and pin the trench and mix/pour the concrete. Started at 6:00am and was done before lunch.
> View attachment 56649
> View attachment 56657
> 
> ...


So you went thru all the work to mix and pour why not just do the easy part? What did it cost to sub the demo out?


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## hardworkingstiff (Jan 22, 2007)

sbrn33 said:


> So you went thru all the work to mix and pour why not just do the easy part?


It could be timing. Sub make take a day or two to get it done and he could finish it right after the prep. It really isn't that hard.

Besides, quality control is much better if you just get it done.


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## sbrn33 (Mar 15, 2007)

hardworkingstiff said:


> It could be timing. Sub make take a day or two to get it done and he could finish it right after the prep. It really isn't that hard.
> 
> Besides, quality control is much better if you just get it done.


That is what I mean. Why not just do the demo also.


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## telsa (May 22, 2015)

*Wet cutting concrete...*

You'll start losing your crew or your back.

More generally, you just can't get decent equipment utilization. 

Every time you turn around, you soon find out that you need yet ANOTHER trick piece of diamond tooling. You can't rent the bits.

FURTHER, it's drastically easier to have ONE sub cut the slab for the plumber and yourself -- and have the tab ENTIRELY picked up by the GC.

It's not a task for the gals, the seniors, or the light-of-frame. 

Further, the slab crew carries their own 'goof' insurance... and there are PLENTY of goofs cut into every day of the year.

&&&&&

I have my own Hilti wet cutting drill. I stay entirely within my zone: branch penetrations for lighting. 

Even with top rated, second hand, equipment my utilization is poor. I own it because of prior experiences being hung up over 'trivial' penetrations through rebar ruining my entire day. 

As for using rental equipment? That stuff is totally TRASHED by the "other guys."

In my area, wet-cutters are on call -- and so ready to hand -- that every EC uses them.

&&&&

As for the rest of my calculations: I schedule other tasks for the 'dead time' that it takes for the cutting crew to do their thing.:whistling2:


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## hardworkingstiff (Jan 22, 2007)

sbrn33 said:


> That is what I mean. Why not just do the demo also.


Since I had been in the P&T business, I was used to saw cutting and pouring concrete so, I would also have done the demo.


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## zach92r (Jun 4, 2015)

Recently had something like this but plumbers were running new lines. (YWCA ie womens ymca) Plumbers core drilling through about 12" of rockcrete (old building) hit 3 electrical pipes took nearly 16hrs of labor to repair. Sometimes you just can't get around doing it by hand....


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## hardworkingstiff (Jan 22, 2007)

zach92r said:


> Recently had something like this but plumbers were running new lines. (YWCA ie womens ymca) Plumbers core drilling through about 12" of rockcrete (old building) hit 3 electrical pipes took nearly 16hrs of labor to repair. Sometimes you just can't get around doing it by hand....


Seems like GPR would have been a reasonable thing to pay for, a lot less expensive than those repairs.


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## btharmy (Jan 17, 2009)

sbrn33 said:


> So you went thru all the work to mix and pour why not just do the easy part? What did it cost to sub the demo out?


It was Friday. Floor prep and carpet Monday. Besides I'm 40+ and am done "humping" concrete to the truck. It was an occupied building and slabs had to be removed. After figuring the labor, cost and liability of the cuts and removal it just makes more sense to sub it out most of the time. I'm a one man crew and would require some cheap help to even consider it.


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## zach92r (Jun 4, 2015)

hardworkingstiff said:


> Seems like GPR would have been a reasonable thing to pay for, a lot less expensive than those repairs.


That's the plumbers i dealt with, they didn't seem all up there either.


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## Theriot (Aug 27, 2011)

Before cutting slab make sure it's not post tension. Cut a cable and watch a cable come flying out the slab breaking everything in its path.


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## ponyboy (Nov 18, 2012)

Theriot said:


> Before cutting slab make sure it's not post tension. Cut a cable and watch a cable come flying out the slab breaking everything in its path.



I've seen tons of cables cut in my time and have yet to see anything as awesome as you just described. It's pretty uneventful really


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## Theriot (Aug 27, 2011)

ponyboy said:


> I've seen tons of cables cut in my time and have yet to see anything as awesome as you just described. It's pretty uneventful really
> 
> 
> Sent from my iPhone using Tapatalk



I have seen one cut about three feet off the outer wall that flew out and knocked over a water fountain. I have always heard stories of these things doing worse. Maybe it's just old BS however. Never wanted to find out. Lol


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## btharmy (Jan 17, 2009)

jrannis said:


> What method are you going to use to come out of that box?


The (almost) finished product.


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## Duane20 (Jun 21, 2021)

aftershockews said:


> Look in


if you place a plastic barrier in the bottom of your Trench run your pvc then run your rear on top and tie every 12 to 24 inchs to prevent floating of pipes


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## Quickservice (Apr 23, 2020)

mcclary's electrical said:


> Oh really?


Good question and how does an inspector ever enforce that?


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## readydave8 (Sep 20, 2009)

Disorienting seeing replies to Aftershock and McClary


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## Wardenclyffe (Jan 11, 2019)

You have insufficient privileges to reply here


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