# Pre-cast core slab



## Black Dog (Oct 16, 2011)

ElectricalDude420 said:


> anybody know the best way to bust octagons in pre-cast core slable flooring? doing piece work trying to do it the most cost efficient way.
> 
> Thanks!


Do you mean remove them?


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## ponyboy (Nov 18, 2012)

Core deck? Octagons? Dafuq?


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## papaotis (Jun 8, 2013)

good questions!


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## CADPoint (Jul 5, 2007)

X-ray! If you need to get through it.

What the structure and the exact situation?

What are you doing that you have to bust it up?

I had to look up what a sable floor was.


Welcome to the forum! :thumbup:


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## telsa (May 22, 2015)

Sub it out to a coring company.


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## ElectricalDude420 (Oct 19, 2015)

core slab*** lol..... was thinking of tracing the box and drilling a buncha 1/4 inch holes then mini sledge and or chissel? anybody do this before?


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## macmikeman (Jan 23, 2007)

I just love the smell of fresh sprung tensioning wires in the morning.


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## ElectricalDude420 (Oct 19, 2015)

im looking for ideas how people installed octagons in core slab for lighting..


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## ponyboy (Nov 18, 2012)

ElectricalDude420 said:


> im looking for ideas how people installed octagons in core slab for lighting..



They put it in the form before the pour. Nobody cuts boxes and pipes into a concrete finish 


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## Bogart (Jul 20, 2015)

ponyboy said:


> They put it in the form before the pour. Nobody cuts boxes and pipes into a concrete finish
> 
> 
> Sent from my iPhone using Tapatalk


Speak for yourself...I went to Home Depot I got myself one of those Precast concrete box cutters and have never looked back...should have picked up a wire stretcher while I was there but forgot:whistling2:


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## ElectricalDude420 (Oct 19, 2015)

you guys dont know what ik talking about lol..... your talking poured slab.....yes we stretch out corline for that before hand... im talking sections of PRE CASTED hollow core floor that is placed on icf styrofoam forms filled with concrete and rebar..... they have bulk heads around alot of the perimetre of the condo units for vents and some wire runs but to maintaint a 9ft ceiling they have core slab painted finish so therefore need to fish ac90 through to a octogon..... mounting a coring drill upside down seems unsafe lol

thanks everyone for a reply im new to the forum


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## telsa (May 22, 2015)

ElectricalDude420 said:


> you guys dont know what ik talking about lol..... your talking poured slab.....yes we stretch out corline for that before hand... im talking sections of PRE CASTED hollow core floor that is placed on icf styrofoam forms filled with concrete and rebar..... they have bulk heads around alot of the perimetre of the condo units for vents and some wire runs but to maintaint a 9ft ceiling they have core slab painted finish so therefore need to fish ac90 through to a octogon..... mounting a coring drill upside down seems unsafe lol
> 
> thanks everyone for a reply im new to the forum


And what about pancakes ?

You're not telling me that the rough concrete surface is the actual finished ceiling. :no:

A deeper penetration (dry cored// wet cored) for fished in MC. 

( Use a blower and a balloon to establish a pull line.)

Use the snap to connect elbow nineties that have recently come out.

There are trick devices (Hilti, et. al.) that can spot the hollows within a pre-cast floor.

So, with such a gadget you mark for the center -- and punch upwards.

Hilti, et. al. have an entire suite of tools for this task. 

Time to contact a sales tech. :thumbsup:

And, lest you've missed it, these are light hand held tools entirely suitable for drilling straight up into concrete. :thumbup:


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## don_resqcapt19 (Jul 18, 2010)

telsa said:


> ...
> 
> You're not telling me that the rough concrete surface is the actual finished ceiling. :no:
> 
> ...


It is in a lot of hotels. Just some "popcorn" texture and paint


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## telsa (May 22, 2015)

don_resqcapt19 said:


> It is in a lot of hotels. Just some "popcorn" texture and paint



Never seen THAT.

But, ... perhaps the light fixtures used have enough of a cover// beauty trim that they can entirely cover a ( surface-mounted ) pancake ?

The trick might be some wedging anchor that can work very well when aligned with a core's tunnel.

http://www.toggler.com/products/snaptoggle/overview.php

Thickness range: 0.375" to 3.625 "

http://www.toggler.com/products/alligator/overview.php

Solid and hollow materials.

With these, there is no octagon box, a simple pancake will do fine.

One need only find the magic spot so that MC can be pulled through the hollow tunnel of the pre-cast element.

I would imagine some off-angle penetration is the trick that lets MC in, easy.

*http://www.aifittings.com/landing/90-degree-connectors*

*This Arlington MC connector would appear to have been specifically designed for this application.*


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## telsa (May 22, 2015)

http://www.fastcap.com/estore/pc/LJ3Pro-Laserjamb-3p18.htm

This is the magic tool that permits no end of grace and speed to alignments, paying for itself during the very first job.

Or...

You can measure off of a seam.


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## johnny_a (Sep 22, 2013)

we have a stand for our roto-hammer that does the job pretty good. its heavy as hell, and makes a ton of noise and dust. ive never had to use it, always had an apprentice/labourer do it. they dont seem to enjoy it much


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## Bad Electrician (May 20, 2014)

If this is cellular precast slabs with a chase in them for designed weight and structural and allowed by the AHJ for wiring, we use to use a hammer and knock out a hole and use a pancake 8-B (3-1/2" x 1/2") round. This was for ceiling work only, never installed floor boxes. But it seems if they are to not be flush with the floor this would work, or use a core drill for flush mount as long as that big a hole does not affect the structural integrity of the slab..


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## ElectricalDude420 (Oct 19, 2015)

I appreicate everyones input!!

i also was thinking pancake boxes but what about the rooms with a cieling fan is a pancake ok to install cieling fan? 

good idea with the balloon and blower....

as far as the rotary hammer stand never heard of it but would be sweet if you could use a stand with 4 inch coring bit!

hope i dont lose money on this job haha


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## Bad Electrician (May 20, 2014)

ElectricalDude420 said:


> I appreicate everyones input!!
> 
> i also was thinking pancake boxes but what about the rooms with a cieling fan is a pancake ok to install cieling fan?
> 
> ...


Supplemental support for the fan boxes would be an anchor in the ceiling.


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## stuiec (Sep 25, 2010)

We did a pipe job in a building with this type of tensioned slab, and were forbidden to penetrate any of the hollow voids. I'd cover my ass if I were you.


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## telsa (May 22, 2015)

ElectricalDude420 said:


> I appreicate everyones input!!
> 
> i also was thinking pancake boxes but what about the rooms with a cieling fan is a pancake ok to install cieling fan?
> 
> ...


I have NEVER seen a ceiling fan that didn't have a beauty cover that would hide a pancake.

HIlti -- and others -- have simply no end of trick fasteners that fill your requirements.

Get a sales tech on the phone. They LIVE for this stuff.

Hilti is never the low ball supplier, but their stuff is state of the art. 

So you get your payoff by way of labor efficiency. :thumbsup:

ITW// Ramset also has some great 'toys.'

http://www.ramset.com/Products/Tools/ToolsbyApplication/MetalFraming/T3MAG.aspx

The T3 is slick -- and avoids the OSHA hassles of powder actuated tools. 

These tools pay for themselves -- during your first commercial job. (of decent size)


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## telsa (May 22, 2015)

http://www.oldcastleprecast.com/products/Documents/AboutElematicHollowcorePlank.pdf

*Old Castle Precast*

3.04 Attachments and Small Holes

A. Subject to approval of the Architect/Engineer, hollow-core plank units may be drilled or “shot” provided no contact is made with the prestressing steel. *Round holes and those less than 8 inches on any side shall be drilled or cut by the respective trades*. Should spalling
occur, it shall be repaired by the trade doing the drilling, shooting or cutting.

If you are bidding // planning -- you need to read this pdf.

I would NOT use a roto-hammer. A diamond drill wet or dry is the way to go.

See, Hilti, et. al.

There are a number of outfits that sell diamond tipped drills -- all of whom get their diamonds from General Electric's synthetic diamond factory.

Google around for them.

Diamond drills produce clean bores. JUST DON'T MISS.

See the pdf for the pattern of tunnels. Then build a jig to locate them -- perfectly. Test your troops on scrap.


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## Bad Electrician (May 20, 2014)

It is fairly easy to determine the center of a core in the project I worked on (43 years ago) simple tapping with a hammer one can find the dead center of the core.

We were instructed by the GC on maximum size of acceptable holes and were told to utilize a hammer to make the hole. Though few contractors had hammer drills in the early 70's, so a hammer was it.


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## telsa (May 22, 2015)

http://www.dynatech.com/diamond-core-bits/

For this application, roto-hammers are not as nifty as a dry diamond bit.

These puppies are slicker than snot.

You don't have any blow out... which is important since one is going to be setting an anchor very close by ... to hold a ceiling fan or some such.

The work goes smooth and fast.

These bits can be mounted to the common angle grinder. Hence, they are lighter.

Did I say that they go QUICK ?

With a jig, you could make an angled bore with perfect repetition.

Dynatech is but one of the players in the market.

These drills are the cat's pajamas for cinder block bores.

You can perform the work -- in-house -- with virtually no training -- as they are simple Simon.






A different jig -- which holds the bit at an angle -- could be cobbled up in short order.

Test every thing on a mock-up. Then shazzam !


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