What do you guys do?

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copper123

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Just wondering about this. Hypothetical question. You are doing some remodel work in old commercial buildings. Your scope of work calls for core drilling some holes for data, power, ect. through 6" concrete floors. Would it be prudent or standard to put in your scope of work that if you hit any old conduits as you core drill that they would be the owners responsibility and not your own to fix the damage? We are doing some work right now and we need to drill 4 holes for 4 - 4" data conduits. The ceiling is pretty high and I just noticed a core hole in the corner. Somebody a very long time ago hit a run of 3 conduits and cut right though them. They obviously re pulled them and now there are just wires free aired in the core gap. That must have been a major bummer. First to hit them, and then to find where they went to and re pull them! Anyhow, If you guys hit something, would it not be your baby to fix it?
Just throwing it out there. Very interested to hear the response.
 
Re: What do you guys do?

just a bit from experience: you can always find what you are cutting into as the wetting solution will be dripping from the lowest points immediately adjacent to the coring. Given this it will be easy to figure the repiping. What may not be so easy to refigure are any sensitive systems that may be powered by any of these circuits.

It would probably be best to put that any problems would be an extra, but requiring someone else to do the repair might generate thinking along these lines: if x won't repair and "A" will, why don't I just hire "A" in the first place. I would assume thatwithout it being stated that there was an assumption of responsibility.

I don't think open conduit is quite code.

paul
 
Re: What do you guys do?

If you pay close attention to the water flow you can tell if you run into a conduit.

Use as little water as possible and if you penetrate a conduit you should notice the water is 'disappearing' as it fills the conduit.

I agree with Paul it would be nice to pass this off but if I was the customer I would hesitate to hire you.

And yes fixing cut conduits is a big time PITA. :(
 
Re: What do you guys do?

It's always been my experience that if we cut them - we fix them. It is usually written in the contract that it would be an " extra " . Just be prepared to chip out more concrete around the cut conduits then make some "slip" couplings
 
Re: What do you guys do?

The best method in highly sensitive areas would be to lay out the cores and then have the concrete x-rayed. Some high profile customers require this before any penetrations can be made.
 
Re: What do you guys do?

thanks,
On my first post I guess I was a little misleading. I think it would be my responsibility to fix them, it just would be for an extra cost. So it sounds like you guys feel the same? If you can't get Asbuilts and the building is old, how can you be responsible??Right now, its a crap shoot. Anybody have any other ideas on how to find conduits encased in concrete without Asbuilts. Can you use some sort of cable locater even if you don't know what ckt would be running through the area. How about some sort of locator that would induce a signal on the entire power distrbution system! Something like one of the X-10 modules! You would just wiggle your little locater in the area where you were going to drill and it would tell you if something was in the area. Just kidding, I am sure they don't make anything that advanced.
 
Re: What do you guys do?

Have any of you tried one of the metal senors that is supposed to find metal in concrete up to 6" deep? I've never tried one, but would really like to find out if they work reliably. They would be a real boon to locating rebar or conduit in concrete before you drill holes.

Zircon makes one that they claim would work:
http://www.zircon.com/SellPages/ScanAndSensor/MT6/MT6.html

If I had several large core holes to drill, I'd order one from someone with a 30-day return policy and try one out.
 
Re: What do you guys do?

Have any of you tried one of the metal senors that is supposed to find metal in concrete up to 6" deep? I've never tried one, but would really like to find out if they work reliably. They would be a real boon to locating rebar or conduit in concrete before you drill holes
Click to expand...
This sounds good but can they differentiate between conduit and rebar? I've seen some decks where you couldn't core a 6" hole without hitting some rebar.
 
Re: What do you guys do?

What I do is drill small test holes with a r/h drill~3/8th bit first.
The time spent is less then repair of one hit pipe!
When drilling the 4"er run the wet vac to pick up the xtra water and have your bucket below for the core water.
I did this on a 9 story dorm not too long ago; PM for the co. thought it was a waste of time untill I showed him the pipe or 2 we would have hit per floor!
my 3 4"risers jumped back and forth depending what hole had pipe; we had big pull box on the wall each floor so you couldn't tell from floor to floor in a closet.
 
Re: What do you guys do?

Originally posted by infinity:
This sounds good but can they differentiate between conduit and rebar? I've seen some decks where you couldn't core a 6" hole without hitting some rebar.
Click to expand...
I don't know - they say they can tell the difference between copper pipe and steel pipe. Maybe the tester will also indicate a difference in the density of solid rebar and hollow conduit? Of maybe with practice you can tell the difference in the diameters?

And rebar should be spaced fairly evenly -- you should be able to spot a conduit on a spacing that isn't likely to be rebar?

No doubt that you will encounter slabs with rebar on 6" spacing (or even double mats), but that would be the exception, not the normal. Most slabs have single-layer rebar spaced between 12" and 24" OC.

Anyway, for under $200 the instrument may be able to help you miss any steel object in the concrete, whether it's rebar or conduit. That would seem worth the price if it works.

I'm sure there will be slabs that it just won't help on, but if it helps on even 50% of them it would be worth the price.

Also, I didn't address some of the other points that copper123 asked in his original post:

I would definitely have a clause in your contract or scope of work that if you cut or damage anything in the slab, then the owner is responsible for the costs of repair (if repair is required). If the owner wants to make you responsible, then you should include the costs of having the slab X-Rayed in your bid price (maybe as an add alternate?) or in your rebillable costs if you are working T&M. Present it so that he has to make the choice -- pay for X-Rays or take the risks himself.

And I wouldn't trust any as-built drawings. If the owner gives some to you to use, the accuracy of the drawings is his responsibility. How would you know if they are accurate? It only has to be off a half-inch.

I'd mark the proposed drilling locations and have him agree with them (sign off) before you drill. I'd make sure it was clear that if you hit anything, it will be his responsibility to pay for the repairs.

I agree that you should make the repairs to any electrical work that is damaged, but it should be at the owner's expense, not out of your pocket.

You better make sure they don't have any in-floor slab heating systems -- that would probably be a real pain to repair.
 
Re: What do you guys do?

Thanks guys for all your replies. I have never heard of the x-ray issue. I will try and look into it a little more. Its a hard choice, if you put it into your S.O.W. document, you might not get the job. But what is the job worth if you hit something??? Tough question. So really what does the 3/8 bit do for you? I am thinking that you are saying you go really slow and be very vigilant, correct? You just keep sucking out the dust and looking and listing for the sounds and signs of conduit?? Also, as a side note, the hole that I saw drilled through, it was all PVC! Does Zircon have a plastic detector?? Just kidding.
Anyhow, thanks a bunch. I think we will drill some small holes first, look and listen and then hope for the best!
 
Re: What do you guys do?

once you hit the pipe, does it matter much if you only cut part way through? It has to be assumed that once the pipe is breached that at least one to several conductors are impaired.

I was inspecting for the Coast guard when it was becoming Homeland Security. An old building with theoretically no live conduit in the floors to be cored. But they xrayed, and almost fried a bunch of equipment as they assumed the xrays were correct. They also ruined some equipment when the pipe filled with water and spilled it on some equipment, missed the really expensive stuff. the ceiling surface piping system was also utilizing the buried piping system such that a cursory examination would lead one to think that the piping on the ceiling was all there was. No money and no time (at the time) to shut the building down to look at every thing.

paul
 
Re: What do you guys do?

Originally posted by copper123:
Also, as a side note, the hole that I saw drilled through, it was all PVC! Does Zircon have a plastic detector??
Click to expand...
Look in the panels and some of the boxes to see if PVC has been used. If PVC was used in the slabs, then a good circuit tracer will probably put out enough signal for you to pick it up. You just have to find the wiring that runs through that area so you can put a signal on it.

And if the Zircon detector will locate copper pipe in a slab, it may also locate copper wire?

I'd give one a try.

If it's PVC in the slab, even drilling just a 1/4" hole, you'll probably drill into the conduit before you can stop, which will probably damage the wire in the conduit.

Using a small (1/4") masonry drill to locate conduit works fine (though it's slow) if the conduit is steel -- the drill bit will stop when it hits steel. I'm sure all of us were assuming that you were talking about steel conduit in the slab.

[ July 14, 2005, 03:23 AM: Message edited by: tx2step ]
 
Re: What do you guys do?

Originally posted by apauling:
But they xrayed, and almost fried a bunch of equipment as they assumed the xrays were correct.
Click to expand...
How in the world did they miss steel conduits in the slabs with x-rays? Even PVC conduits should have been obvious. :confused:

All the x-rays that I've seen gave a very clear picture. Was there something unusual about it?
 
Re: What do you guys do?

I didn't see the xrays, only was told that the core areas were clear. It is possible that not being thetre the day that they "said" that they were going to xray was a mistake.

They had won a "war" claiming to my PM thatI was overzealous, with my PM located two states away. This created a situation where I had to decide to save credibility for big issues. Unfortunately this is a common situation with new minority contractors in gov't contracting.

The officer present indicated that although he did not witness what was done, "something" was, so I had no actual peek at the stuff and had no reason to suspect that they wanted to shoot themselves in the foot, if in fact, that is what they did.

paul
 
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