Drilling Holes Through Concrete

 
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Old 03-09-2011, 05:33 PM   #1
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Drilling Holes Through Concrete


I'm starting a job soon in a commercial setting. I have 4" concrete slab poured over the corregated metal sheathing. I'm looking to use a core drill to drill about 12 holes 2-1/2". My question is, can a core drill, drill through the metal corregated sheathing or do I need other tools? Thank you in advance for the help.
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Old 03-09-2011, 06:21 PM   #2
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Re: Drilling Holes Through Concrete


The answer isn't so much "can", but "should you".

Yes, the diamond bit can go through the metal, but chances are your going to tear the teeth up.

The other question is why would you? If you know the slab's thickness, core out the concrete, vac the hole, and use a bi-metal hole saw the diameter of the core to cut the decking.

The last thing, and really important is knowing if its PT. If your not certain, have you x-rayed the slab? If you hit one of those cables, your in for a world of trouble. Core machines will go through rebar, conduit, etc..easily.

You need to make sure you know what's in and under the slab first.

Good Luck.

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Old 03-09-2011, 08:04 PM   #3
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Re: Drilling Holes Through Concrete


We know for a fact there is rebar and corregated decking being used. Haven't used an xray though. We have building plans. Would it say in it weather there is PT cabling involved? The corregated decking is spanning across the room perpendicular to this space being used for this resturaunt. Kind of a long rectangular space. Basement is underneath the decking. The span from wall to wall is about 15-20ft wide x 75' length. Under the decking there is space between the decking and finished drywall ceiling. With signs of rebar, decking spanning perpendicular to length of space would there still be PT cabling inside this slab? I appreciate the chime in

This work is being done on a mini mall type of setting with businesses on each side of the space being worked on.

Last edited by RocknTJ; 03-09-2011 at 08:21 PM. Reason: forgot to add some detail
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Old 03-09-2011, 08:42 PM   #4
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Re: Drilling Holes Through Concrete


Do you have access to the original funnies?
Do you have an engineer involved?
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Old 03-09-2011, 09:14 PM   #5
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Re: Drilling Holes Through Concrete


I'm just the laborer/tech on this job. Helping out a plumber. But I try to make sure this plumber knows what he's getting into so we don't get into some serious poo poo. I've studied construction management in school and currently hold a class C HIC license but working towards getting my master's plumber license soon along with moving up to the class B or A. I'm not sure if an engineer approved the plans? I'd hate to loose any of my appendages due to ignorance.
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Old 03-09-2011, 09:17 PM   #6
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Re: Drilling Holes Through Concrete


We recently framed a commercial building for a florist and the GC called in a company to do all the drilling. They had a trailer mounted generator with electric coring drills. I would looking into something like that.
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Old 03-09-2011, 09:31 PM   #7
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Re: Drilling Holes Through Concrete


We would be electric core drilling but this is not the issue I'm seeing here at the moment. It's knowing weather there are PT cables embeded in the concrete? Do they even put PT cables in 4" slabs?
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Old 03-09-2011, 10:23 PM   #8
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Re: Drilling Holes Through Concrete


I've done thousands of cores. It is exceedingly rare for pan decking to contain PT cables, but certainly not impossible. PT slabs are thick, most often with a substantial clear span. Pan decking is used with thinner slabs, on columnand beam steel construction, with clear spans generally 12 to 22 feet.

As far as the core driller penetrating the pan decking, it has been done millions of times. Disregard anyone who states otherwise.
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Old 03-10-2011, 12:21 AM   #9
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Re: Drilling Holes Through Concrete


Yup, disregard it.

Just make sure you put in all that extra money for replacement bits.

As I said before, it can be done, but shouldn't for the sake of excessive wear and tear. Especially when it's just as simple to have a guy come behind you with a hole saw to finish the job. It's not adding any significant labor costs (corrugated decking? what, 45 seconds total?) , and your preserving the bit for what it's meant to do..core concrete.

Also don't forget that mother can bind up in the hands of an inexperienced operator.

Wingnut is absolutely correct about the PT cables though. there used in thick slabs and long, clear spans.
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Old 03-10-2011, 12:38 AM   #10
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Re: Drilling Holes Through Concrete


I've drilled several hundred cores thru pan deck, caught about a thousand, vacuumed up the water from about two thousand cores, and have been the superintendent for about three thousand cores. Our drillers have no concern about drilling thru pan. Also, I have found that using a hole saw to finish out a core thru pan is a sure way to ruin a hole saw, because of grit and concrete remnents. I suggest you ask a reputable core driller about this. Seems like Mud Master and I are on complete different sides about this, but since I've been doing this since I dropped out of grad school in 1985, my money is on me
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Old 03-10-2011, 01:31 AM   #11
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Re: Drilling Holes Through Concrete


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Originally Posted by Anti-wingnut View Post
I've drilled several hundred cores thru pan deck, caught about a thousand, vacuumed up the water from about two thousand cores, and have been the superintendent for about three thousand cores. Our drillers have no concern about drilling thru pan. Also, I have found that using a hole saw to finish out a core thru pan is a sure way to ruin a hole saw, because of grit and concrete remnents. I suggest you ask a reputable core driller about this. Seems like Mud Master and I are on complete different sides about this, but since I've been doing this since I dropped out of grad school in 1985, my money is on me
It's your money, do with it as you please.

I as well have been a foreman, superintendent, project manager and president of many many large and small builds & renovations. As an employee, I ran projects in the multi-millions. As the owner of a division 09 corporation I as well ran projects in the hundred thousands and millions. I have now merged my corporation with my fathers 30 year commercial contracting firm(that I came up with), as president and now choose to run projects in the thousands to hundred thousands.

I as well have cored thousands of holes, for bollards, dining room tables, fence posts, speed rails, structural columns, the list goes on. So, please don't think your credentials exceed mine. I've logged enough hours on my machine that I had to retire it and purchase another.

And your correct, it does wear out the hole saw, but the hole saw is a hell of a lot cheaper than the core bit.

Your also correct that we won't see eye to eye on this. I never once said it wouldn't do it, I said there's a better alternative, and I'll stand by that.

Your incorrect in your thinking that you are the only knowledgeable commercial contractor on this board. I'm sure you are very knowledgeable, and I won't dispute that...but I'm overly positive that I will stand toe to toe with you on any trade, code, regulation or specification you can think of. Please don't insult what I've spent decades learning and perfecting.
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Last edited by Mud Master; 03-10-2011 at 02:02 AM.
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Old 03-11-2011, 08:16 AM   #12
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Re: Drilling Holes Through Concrete


So I cored 6 holes yesterday with no issues except it took longer than expected. Now I need to find a good hole saw to cut decking with. Thanks for posting MM & WN. I found both posts helpful.
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Old 03-11-2011, 11:54 AM   #13
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Re: Drilling Holes Through Concrete


Really? You think that a diamond bit is going to wear out that much faster?

I don't see the logic in this. It's a DIAMOND bit, thats lubricated with water! Minimal wear. Whats the trade off for the extra labor to use the other saw, and prep the hole to use a bimetal saw? I put money on Not worth the time and effort.

Next you'll me telling me not to use my concrete chainsaw because I may hit rebar. Absolutely ridiculous man. Come on now has common sense gone out the window?
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Old 03-11-2011, 10:44 PM   #14
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Re: Drilling Holes Through Concrete


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Really? You think that a diamond bit is going to wear out that much faster?

I don't see the logic in this. It's a DIAMOND bit, thats lubricated with water! Minimal wear. Whats the trade off for the extra labor to use the other saw, and prep the hole to use a bimetal saw? I put money on Not worth the time and effort.

Next you'll me telling me not to use my concrete chainsaw because I may hit rebar. Absolutely ridiculous man. Come on now has common sense gone out the window?
It comes down to personal worth.

Someone that cores everyday and figures a new set of bits every 4-6 months will care less than someone that cores on projects 2-3 times a year and doesn't want to have to replace those expensive bits. If you take good care of them they will last a long time.

I have 40+ diamond blades for my hand held dry saws and walk behind wet saws, and I have learned if you don't take care of them they will dull out quickly and your left at the counter buying more.

Need vs. Want.

And actually the machine will go through rebar fairly easily, but your gonna feel it for sure.

You also made my point about using the core vs a hole saw in your second paragraph. It's minimal labor to have a helper, who would probably be standing there whisking water away anyway, take a few seconds to cut the decking out. I'd rather have my mechanic moving on to the next hole.

This is a good argument though. Certainly shows how different guys go about things.
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Old 03-12-2011, 12:02 AM   #15
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Re: Drilling Holes Through Concrete


Yeah very true people do things differently. I wouldn't want to have 2 guys drilling cotes. Plus your hosed I'd you hit the part of the decking where there its an elevation change.

But there is more than one way to skin a cat. If you get it done and make money, that is the name of the game.
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Old 06-12-2011, 07:36 AM   #16
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Re: Drilling Holes Through Concrete


Core bits are designed to cut thru concrete and rebar, a little bit of pan deck is a piece of cake.
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Old 06-15-2011, 11:01 AM   #17
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Re: Drilling Holes Through Concrete


FWIW I'll second anything that follows using the right tool (bit) for the job. It's one thing if you only do a few jobs per year, but if you're on it daily, then you're just going to cost yourself a lot more money. In this case, I'd cut out the concrete and use a hole saw that matches the original hole to cut through the decking.
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Old 06-15-2011, 02:30 PM   #18
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Re: Drilling Holes Through Concrete


I have core drilled in Out of the ordinary locations, mostly manholes and concrete sewer structures. The thin metal from the room is not going to phase the diamond core bit. What might happen would be is that you would get a shard of metal break off and bind the bit. I have had that happen a few times. But I was drilling an old sanitary manhole structure and got into old cast iron that was imbedded in concrete. I also cores a 12" hole through a concrete structure that took nearly 3 hours to core through because the bit hit a piece of rebar on end. The metal will not hurt the bit but it might bind the bit if a piece comes off

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