Rebar detector

[bluedog225]

With all the modern wonders available these days, I was wondering if there is an affordable way to detect rebar in concrete prior to drilling? I need a 2 3/8” hole in a 10” concrete wall to run a piece of rigid metal conduit. The 5/8” rebar is on 12” centers horizontally and vertically.

E.g., I see the MetalliScanner MT 7 metal detector at home depot.

It would be great to avoid the steel. I’m tempted to try a rotarry hammer core bit with my bosch bulldog instead of a big stationary core drill. Would be a lot cheaper than the rental of the stationary unit.

Does anyone have experience with something like this?

Thanks

 

[strutaeng]

Not really affordable. Ground penetrating radar (GPR) is best, but there are other means and instruments to locate rebar. We have a GPR little handheld, and a Hilti (can't remember the model). The Hilti is pretty much a glorified stud finder. Those are really limited on how deep the rebar is. Is this a wall, beam or a slab?

There's a company called GPRS that I've used before. They are all over the state. Not sure what a trip charge is these days.

 

[mike93lx]

In my experience, if I tried to hit the rebar, I'd miss it, so maybe try that approach?

 

[RPH]

We used induction heating coils that were flexible. They would be wrapped around columns or laid out on the floor. They would heat the steel and thermographic photo solved the location. Worked great on the historical restorations in Europe.

 

[nolimits76]

Several years back we had a supplier drop off one of the radar machines for us to sample. Their intent was we’d fall in love and order a few. Cost was pretty substantial and feedback wasn’t great so we never bought one. I’m sure technology has improved but we still don’t have one.

As mentioned GPRS is a firm that travels around and scans your concrete. They have a green box guarantee that if you core/cut in their defined limits they guarantee no obstructions or they pay for the damage.

I’m relatively certain you won’t like their quote but it’s worth a call to check prices. They do advertise doing residential work. Personally I’d be more inclined to use something like this when you have a costly or dangerous element involved such as post tension cables, electrical conduit banks, etc.

Utility Locating, CCTV Pipe Inspection, Concrete & Laser Scanning

GPRS provides nationwide infrastructure visualization and data management via ground penetrating radar (GPR), Utility Locating, Concrete Scanning & Imaging, Video Pipe Inspection, 3D Laser Scanning, Leak Detection, and SiteMap® GIS data services.

www.gp-radar.com

 

[nolimits76]

In my experience, if I tried to hit the rebar, I'd miss it, so maybe try that approach?

LOL that’s about my luck too!

 

[mike93lx]

Several years back we had a supplier drop off one of the radar machines for us to sample. Their intent was we’d fall in love and order a few. Cost was pretty substantial and feedback wasn’t great so we never bought one. I’m sure technology has improved but we still don’t have one.

As mentioned GPRS is a firm that travels around and scans your concrete. They have a green box guarantee that if you core/cut in their defined limits they guarantee no obstructions or they pay for the damage.

I’m relatively certain you won’t like their quote but it’s worth a call to check prices. They do advertise doing residential work. Personally I’d be more inclined to use something like this when you have a costly or dangerous element involved such as post tension cables, electrical conduit banks, etc.

Utility Locating, CCTV Pipe Inspection, Concrete & Laser Scanning

GPRS provides nationwide infrastructure visualization and data management via ground penetrating radar (GPR), Utility Locating, Concrete Scanning & Imaging, Video Pipe Inspection, 3D Laser Scanning, Leak Detection, and SiteMap® GIS data services.

www.gp-radar.com

Hitting a piece of rebar for a single core is inconsequential. I can't imagine paying for radar in this case

 

[bluedog225]

This thing might be worth a shot. The rebar is roughly halfway in the middle of a 10” wall.

 

[Garcky]

That Zircon finder downthread will probably be adequate for most needs, I think. I rely on my stud-finder version, which also detects wiring in typical home walls. I've had it for years, and it has never failed me. Cheap insurance, either way.

 

[bluedog225]

Hitting a piece of rebar for a single core is inconsequential. I can't imagine paying for radar in this case

Agreed. But so much easier a job to miss it. I hate grinding away at a piece of rebar knowing I’m destroying my new bit.

 

[duneslider]

I have never seen anything diy friendly that worked well. We regularly have to hire a company to come in and map floors for us to locate electrical conduit or other metal in floors. Not sure what technology they are using but isn't DIY cheap and they are always booked out.

We also regularly cut through rebar in concrete with wet saw hole saws, the diamond blades don't much care about rebar. We also use Rebar Eater/Rebar cutter bits in the hammer drills all the time too. We don't ever use dry core saws. We have to follow so many rules with the dust its easier to do bigger holes with water and all the smaller bits are the hollow bits hooked to the hepa.

 

[mike93lx]

Agreed. But so much easier a job to miss it. I hate grinding away at a piece of rebar knowing I’m destroying my new bit.

No argument there

 

[ipgenie]

I don't have any suggestions regarding the rebar detection.

I used a 2" bit like that to cut a few holes in a floor for conduit to come up into a wall cavity. It worked great but I sure don't envy your wall bore. I was really glad to have gravity in my favor so I could just lean into it a bit and let it chug its way through. Holding it up in the air and pushing it through the wall will be a good workout. Be sure to eat your Wheaties.

 

[Augus7us]

My recommendation:

I've used both a rotary SDS Maxx and a core drill.

Rent the core drill. No comparison between the two in my experience. Cut out a 3" hole like it was butter. Quick and smooth.

The only caveat is I've never used one on a vertical wall. They are designed to be mounted to the wall but they are heavy, get a friend to help you out.

Edit: Forgot to mention you can forget about rebar with the core drill. If you hit any you will not know it.

 

[mike93lx]

My recommendation:

I've used both a rotary SDS Maxx and a core drill.

Rent the core drill. No comparison between the two in my experience. Cut out a 3" hole like it was butter. Quick and smooth.

The only caveat is I've never used one on a vertical wall. They are designed to be mounted to the wall but they are heavy, get a friend to help you out.

Edit: Forgot to mention you can forget about rebar with the core drill. If you hit any you will not know it.

I think a core drill vs a sds is similar to the sds vs hammer drill comparison. Amazing the difference between them for their intended purposes

 

[Jeff Ivers]

Has anyone tried a treasure hunting type metal detector? I use a Garrett AT Max and frequently get hits when I approach or scan over sidewalks and driveways.

 

[wssix99]

Do you have any other penetrations in the wall? You could just measure 12" increments off of that and bank on the other penetration avoiding the grid.

 

[bluedog225]

I was thinking no other penetrations. But your comment got me thinking and I had to dig up photos from years ago. I want to go out the wall on the left, but no head on shot of that. Darnit. But the wall on the right, I might be able to pick a good spot based on the slab and the wall ties. Thanks!

 

[Imatk]

GPRS scanned my floor, was only a couple hundred bucks I think... completely worth it (and for me necessary)

 

[PugetDude]

I can find a piece of #4 rebar with a 3/16" bit just about every time I drill into concrete. If I was closer I'd come over and mark the walls so you'd know to drill elsewhere.

 

[kbs2244]

I would not worry about hitting rebar

years ago I put two 5 inch hole through a 10 inch concrete block wall that had the voids filled with rebar and concrete

I bought the hole blade and rented the 3/4 inch drill from Home Depot

it was an interior wall and I did not know that it was filled

the hole blade went through the rebar without my knowing it was there until I removed the cores and saw the cut metal ends in them

a 2 3/ 8 inch hole would be easy

 

[wssix99]

But the wall on the right, I might be able to pick a good spot based on the slab and the wall ties.

If you have an unused sample of the rebar, you can count the ridges on the bar to figure out the measurements. (Each mill can have a different pattern and I can't see any of the mill marks in your picures.)

I have ICF walls and needed to do similar methods to find some of my ties. If you measure distances off from the corner of the building, keep in mind that the rebar is in the middle of the wall, so your first bar will be less than 12" from the corner on your inside measurement and then more than 12" from the corner on the outside measurement.

 

[rayra]

Agreed. But so much easier a job to miss it. I hate grinding away at a piece of rebar knowing I’m destroying my new bit.

Bits are a consumable.

 

[no704]

Can the bar be available on the exterior? Run a current thru it and look for heat?
Or get a stupid powerful neo magnet and you could get a good enough guess. I had one that would stick a 16” tool box to anything with 5” of foam around it.

 

[bluedog225]

Interesting thought. I’ve got a 3” neo. I’ll give it a try.

 

[nadogail]

For overhead core drilling I suggest you put an anchor into the ceiling and support your dril from that. I am sure you will find it easier than trying to push your core drill up. I see concrete cutting services using anchor bolts when sawing walls and drilling overhead. The biggest problem will be water control.

 

[MBfreak]

I use a super strong magnet and drag it across the surface. With a bit of practice, quite accurate.
A good source of magnets is the PM in a scrapped hard-disc.

Ola