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Posted By: renosteinke Rebar Radar - 07/11/15 01:48 PM
I have it!

Yup.... Hand mr a roto-hammer, point me at a block wall, and I'll find the rebar, at least three tries out of four.

So ... here's the question ... anyone have any tricks for cutting rebar in the wall? My carbide core bits barely scratch it. There isn't room for a saws-it-all to get in there, and a cutting torch isn't part of my kit (maybe it needs to be!) Hole saws need a solid center for the pilot to guide the bit - and by the time I find the rebar, I've taken the center away.

Yesterday's project involved connecting an MCC to the gutter on the opposite side of the wall behind it. It's not like I could move the holes over an inch.
Posted By: gfretwell Re: Rebar Radar - 07/11/15 05:57 PM
Diamond tools will cut rebar but it is very hard on the tool.
Posted By: twh Re: Rebar Radar - 07/11/15 07:26 PM
Depending on the size of the hole and the distance between the re-bar in both vertical and horizontal directions, it's probably unlikely that you could drill a number of holes and not hit re-bar. Sorry, but it might not be a super power. Still, you can change your name to "Rebar" and everyone will understand.

When the hole location has to be exact, plan for failure and hire someone with one of those wet coring machines. They cut re-bar nicely. They also do a sweet job of cutting hidden conduit in the cement.

It seems to me that if you stick a torch in a hole that isn't all the way through, it doesn't work.

Posted By: electure Re: Rebar Radar - 07/12/15 05:53 PM
Some tool rental outfits rent core drills.

United Rentals is one of them. I see there is one in Blytheville.

Make sure to get the damage waiver (insurance).
Posted By: renosteinke Re: Rebar Radar - 07/12/15 10:12 PM
I see that $55 will get me a Bosch bit that is specifically designed for cutting rebar, and fits in the hammer drill:

Bosch RCSS2168

http://www.boschtools.com/Products/...tegory.aspx?catid=1099&subCatId=1613

The idea seems to be that you use the usual masonry bits until you hit steel, use these bits to cut the steel, then resume with your usual bits. Interesting.

Has anyone used them?

A 1-1/8 bit ought to fit neatly into the hole you're making for 3/4" pipe. Looks promising.

For larger holes - my current project involves 3" pipe - I bet you can make smaller holes to the side of the main hole, cut the rebar, then break it out. Maybe. If you're going to do that, you probably want to remember that most rebar you'll find in block walls is about 3/8" diameter; maybe a smaller bit is in order.

I don't object to renting tools - core drills, btw, are also rented by Home Depot - but there is a time penalty. This job is just outside Memphis, so rental access is no problem.
Posted By: HotLine1 Re: Rebar Radar - 07/13/15 01:22 AM
As twh said, the core drills from the guys that do core & cutting work real great.

Mark out the location(s), make the call, watch them work, & pay the fee.

Works really painless & great.
Posted By: gfretwell Re: Rebar Radar - 07/13/15 05:10 AM
I am not sure whee you see #3 rebar used for much of anything except the bottom and sidewall grid in a swimming pool. A doweled cell (block core poured solid) in Florida requires a #5 that hooks to the footer steel and the tie beam steel on top.
Posted By: brsele Re: Rebar Radar - 07/15/15 01:13 AM
If you're interested in a dry diamond core bit, I've received good service from this place: http://buydrillbits.com/.
But as Greg said, it is very hard on the drill. I'm pretty sure that I killed my Bosch.

Actually I have considered buying a proper water cooled Hilti core drill and offering my services. Anybody here know anything about that type of business?

Bruce
Posted By: Potseal Re: Rebar Radar - 07/15/15 06:38 AM
I used to work with a smaller construction outfit that tried doing their own core drilling. Eventually two things happened:

(1) depending on the location we first called in a guy to X-ray the wall or floor

(2) next we called in the guys who specialize in drilling cores

Worth every cent.
Posted By: gfretwell Re: Rebar Radar - 07/15/15 03:17 PM
Pot seal has a valid point with the X-ray. If that rebar was not part of the engineering of the building, the builder would not have put it there. That is particularly true in floors.
Posted By: HotLine1 Re: Rebar Radar - 07/16/15 12:00 AM
Now there are three votes to call a pro!!

Those expensive diamond core drills go thru anything in any wall I ever encountered.

Sawcutting slabs is a 'ditto'.
Posted By: twh Re: Rebar Radar - 07/16/15 12:21 AM
Originally Posted by Potseal


(1) depending on the location we first called in a guy to X-ray the wall or floor



Who does that?
Posted By: renosteinke Re: Rebar Radar - 07/16/15 01:27 AM
Let's not over-think this.

I mean ... X-ray? Really? We're not talking a pre-stressed concrete floor- we're talking about the typical block wall, where we make countless holes for 3/4" EMT daily.

Nor are we likely to contract THOSE holes out. Yet, just 'brushing' against rebar is enough to ruin a good hole.

I haven't put a ruler on the rebar used in block walls, especially for the "bond beam." Heck, it might be 1/2" some of the time .... but it sure isn't 5/8"! That's a pretty hefty rebar, something I only rarely see, and then in substantial foundation pours. That discussion, misses the point: rebar is sure to be a fraction the size of the hole you're trying to make.

This thread was inspired by a series of holes I needed to make for 3" pipe. Invariably, I'd catch the rebar along the edge of the hole. It's a real puzzler when the holes for pipes #1, #2, and #4 sail clear through ... yet hole #3 manages to catch steel along one edge. You can't move that hole, and even a small 'adjustment' is difficult with the bulk of the hole already made.

So far, I don't think anyone has tried that Bosch 'rebar cutter' bit, in any size. Pity. I suppose I'll have to front the $55 and find out firsthand. If I do, I'll be sure to make a report.
Posted By: brsele Re: Rebar Radar - 07/16/15 02:47 AM
Originally Posted by renosteinke
we're talking about the typical block wall,

Actually, I've never seen a block wall with rebar.
However, around here, the flavor of the day is ICF, which has a lot of 1/2" rebar. And the building inspectors have no problem with making a hole through where there's rebar.
Posted By: HotLine1 Re: Rebar Radar - 07/16/15 03:22 AM
reno:

OK, time for me to clarify what I said above.....

3" and up holes in concrete (poured) walls (all w/rebar), are what I called the pros for. Also, any saw cutting slabs was left to the pros. (Think a critical hole or cut)

I favored Bosch 'Bulldog' hammer drills, w/SDS bits for holes up to 1". Black & Decker Macho hammer drills for core up to 2". Yes, when the occasional rebar was found, the hole was adjusted as needed, These were not critical holes, so no big deal.

BTW, as Greg said, rebar is common in block walls here; mostly #4 or #5. (1/2"-5/8") Some poured walls have #7, and many spec slabs have #8.

Posted By: gfretwell Re: Rebar Radar - 07/16/15 08:10 AM
In Florida the tie beam need 4 #5s, there is one in each doweled cell (corners, both sides of any window or door and every 4' on a running wall) and 2 in the footer. These are all wire tied together to make a matrix.
If the beam is load bearing, you may have four #7s and two #5s. Every one of them is part of the engineered assembly and cutting one is about like cutting truss chords.


[Linked Image from gfretwell.com]
Posted By: HotLine1 Re: Rebar Radar - 07/17/15 01:34 AM
Greg:
Is this a residential, or commercial??

Looks real heavy duty.
Posted By: gfretwell Re: Rebar Radar - 07/17/15 05:57 PM
My house. Florida has a tough building code ... hurricanes.
I imagine the steel in that beam is probably what the engineer would spec anywhere tho. This is carrying the corner of the roof from a column 5' away. I have a 9x9 corner slider there.
A regular tie beam that is only there for uplift will have four #5s.
Posted By: Potseal Re: Rebar Radar - 07/18/15 07:21 AM
Like someone already mentioned "rebar in block wall?".

That's new to me, too. I really thought that the OP meant poured concrete with rebar.

Any block wall that I've drilled into there was only one concern and that was hitting conduit or other. Otherwise, draw a circle and use the longest 1/4" bit you can find and drill as many holes as possible. Then knock it out with a hammer.

But if rebar is involved then I can't offer anything since I have yet to encounter block walls with rebar.
Posted By: gfretwell Re: Rebar Radar - 07/18/15 08:51 AM
This is a typical block wall in Florida. The pictures were taken to show the UFER connection but you can see all the "hooks" that will form the rebar matrix when the the hooks are dropped in from above and tied to the bottom hooks.
They paint the Ufer green so that cell doesn't get poured solid like the rest

[Linked Image from gfretwell.com]
Posted By: HotLine1 Re: Rebar Radar - 07/18/15 04:17 PM
Greg:
Thanks for the nice detail pics.
Pics say a 1000 words.
The 'green' rebar is the ufer, and that is green spray paint, correct.

Green rebar up here is epoxy coated to slow corrosion.
Posted By: renosteinke Re: Rebar Radar - 07/18/15 04:41 PM
Those are some interesting pics. Greg. I've never seen a block wall made in quite that manner.

I wasn't so clear about block vs. concrete. I haven't seen many concrete walls.

The 'block wall' I am most familiar with - a style seen in Illinois, Nevada, and Arkansas, so forgive me for thinking it was the common method - starts with a concrete slab. Or, at least, a concrete footer.

There will be rather short bits of rebar either poking out of this concrete in select locations.. These pieces are likely to be either 3/4" or 1/2" rebar; 5/8" just isn't commonly used. You usually START with a copper wire set in this concrete for the Ufer.

The rebar is run vertically in only a few select locations, usually near corners and doors. Most often, the block is not the primary structure; there's proper steel for that. Block only fills the spaces between the columns.

Usually there are only a few courses of block where rebar is run horizontally. Bottom, top, and one somewhere above the half-way mark seems to be the practice. This rebar is a lot smaller, perhaps 1/2". It's pretty much just laid in a groove that is manufactured into the blocks, tied to the verticals and each other, and buried in mortar.

Windows and doors have a piece of steel- often angle iron- used as a header. (Not always; I've seen 8-ft. garage door spans made without anything but filled block, not even rebar to tie it all together).

That brings up another relevant point: TIME. Whatever is being done today, you can't expect that to have been the way they did it even last year ... let alone during our childhood. There have been major changes. The excuse varies (hurricanes, earthquakes, whatever), but the result is the same .... there's no telling what you'll find.

The rebar generally doesn't sit plumb and level within the block - especially where pieces overlap. It's often bent or tilted. The result is that you can miss the rebar completely in your first three holes, then run into it on the fourth. You need not run into it by much ... just 1/8" of contact is enough to catch your bit or stop your core drill.

(That's right ... I generally use core drills for everything larger than 1/2")

So, punching a hole in block is a crapshoot ... you either have the hole made in a heartbeat .... or it takes half a day. The difference? Rebar. That's why I'm looking for a better way to deal with rebar.
Posted By: LarryC Re: Rebar Radar - 07/19/15 02:40 AM
I don't work in the field. A friend who worked in broadcast radio made the comment about a building he worked in, that had a high power FM transmitter in the building. He stated he could follow ANY piece of metal pipe in the building by using a little transistor radio.

I wonder if that effect could be used to trace rebar in a wall by hooking a little 15 W transmitter to the accessible rebar and tracing the metal. Something similar to a pair finder tracer.

Larry
Posted By: gfretwell Re: Rebar Radar - 07/19/15 08:10 AM
There are 2 styles of wall here. One uses a "U" shaped lentil block over doors and windows that gets 2 #5s and then a course of block with the "U" cut out at the top for the second pair of #5s. These 2 courses are poured solid along with the doweled cells.
The other method starts with the block built up to the top of the windows and doors and the whole top 16" is one solid pour.
"hooks" #5s with a 1' bend at the top are tied to the tie beam steel and go down in the doweled cell where it gets tied to the ones coming up.
That is the way this one was done.

[Linked Image from gfretwell.com]

[Linked Image from gfretwell.com]

John, yes the green one is the Ufer. a #4 copper wire tends to be gone before they get ready to set the panel. There is always a fight about whether it is legal since it is not "encased" in concrete. If they really insist, that core gets poured solid after the acorn and #4 goes on.
The paint is marking paint and the rain will wash it off before they finish the wall most of the time. If not, they wash it off.
Posted By: geoff in UK Re: Rebar Radar - 07/19/15 10:28 AM
Its interesting to see the different building techniques used in various places. There is a huge variation between North and South of Europe, reflecting climate differences, and in some places earthquake risks. I am sure the same must apply across the States.

The last two pictures resemble to me methods I've seen in the South of France in a relative's new house. Single hollow block walls with some re-bar and a poured concrete "top" which I was told was an earthquake safeguard. In UK the norm is double,(i.e. cavity) walls with insulation between the layers, making an outside wall 12 inches thick
Posted By: gfretwell Re: Rebar Radar - 07/19/15 05:30 PM
Florida leads the world in hurricane resistant construction and Miami Dade is the leader here. The problem with (hurricane) Andrew was not that the code was weak. It was that the inspections were weak to non existent out in the unincorporated county. There was a big shakeup in Dade county, merging it with Miami but the biggest difference was a change in the whole building code system in Florida. We now have a uniform building code state wide and state licensed building code officials. They also beef up the code just about every cycle. One thing you don't see here is houses knocked off the foundation and floating away. You also do not see the roof coming off. You might lose the shingles but the structure will still be there.
Our latest wind code map has most of the southern peninsula with a 140MPH or above rating and it is 180 down in the keys.

[Linked Image from gfretwell.com]
Posted By: HotLine1 Re: Rebar Radar - 07/20/15 02:06 PM
Greg:
Thanks for all the info.
I've only seen one (1) SFD that was built similar to what is in your pics. It has been 2-1/2 years in 'progress'.

Posted By: gfretwell Re: Rebar Radar - 07/20/15 08:57 PM
My wife was banging them out, 2000-3500 sq/ft, in 12 to 16 weeks. The cycle time was 16 weeks but if the bonus was right she could shorten up that time frame wink
The 12 week house netted her a $8k bonus.
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