Drilling concrete with rebar

[artrem]

So we moved into a new house with a 3-car garage and I'm poised to install my Maxjax. I drilled the holes and installed the anchors with no problems in my previous garage but that slab was reinforced with fiberglass. This garage slab is reinforced with rebar on approximately 12" centers. This is a good thing, but I'm hesitant to start drilling because I have no experience drilling through rebar.

I'm concerned that the bit might catch if it hits the edge of a rebar and mess up the hole. Just wondering if anyone with experience could tell me what to expect when I hit rebar. In anticipation, I bought a rebar cutter. How well do they work?

I also got a rebar finder, but it's not very precise and I don't think I can accurately locate all the rebar under the column mounting locations.

This garage is a bit small and I'm still on the fence about this. I may sell the Maxjax and get something else but once you get used to having a lift it's hard to go back.

 

[mike93lx]

Use epoxy anchors and you don't have to worry about the hole not being perfect

 

[Buckgnarly]

I hit rebar on my install, rebar cutter went through it like butter.

 

[dcg9381]

You can buy bits designed for rebar... I think you're doing it right - try to locate, try an anchor, but if those don't work, just go through it.

 

[nadogail]

Sometimes it will not be as easy as it looks in the movies.

 

[Copymutt]

I have wiped out carbide concrete bits hitting rebar. Now I locate the rebar w/ a cheap metal detector.

 

[ConCretin]

Well in the first place, odds are you won't hit rebar. If you are unlucky and happen to hit a bar, there are drill bits made for this purpose. Carry on and get your lift installed.

 

[DaveInHouston]

I’ve got #3 rebar on 16” centers in my slab. Got lucky with my lift and didn’t hit any.

 

[wssix99]

Well in the first place, odds are you won't hit rebar. If you are unlucky and happen to hit a bar, there are drill bits made for this purpose. Carry on and get your lift installed.

^ This.

This is what a rebar cutter looks like. They are not cheap...

You can buy one and have it on-hand in case you need it. (Start with a regular bit and then switch to this if you hit bar.)

^ Your local hardware store may not have a good supply of these, but Grainger will have them.

 

[Scoobis]

wow will be mounting an air compressor to the floor this week, i hope i don't hit rebar

 

[Retroman]

Drilled and set anchors in concrete for 30+ years, If you hit rebar chances are small it would damage your bit. Drill the holes if you hit rebar then get a rebar cutter and your good.

 

[like2wheel]

What about welded wire mesh?
Concrete guy used standard stuff, but I added a sheet of heavier (10 or 8 ga?) stuff at each post location.

Should I have a rebar cutter on hand when installing my lift, or will a regular bit go through that?

 

[DaveInHouston]

Depending upon your rebar layout the odds off hitting the rebar are pretty slim. Likely less than 3%. I installed air compressor and 2 post lift in my shop. Never hit anything. Like Retroman said, if you do, go get a rebar cutter.

 

[artrem]

Thanks guys for all the comments. I was just wondering if when the bit encounters rebar it just stops, or if there was danger of the bit catching and twisting the drill, messing up the hole and possibly my wrist. The bit I have was only used to drill the 10 holes in the previous install and the rebar cutter is brand new.


The photo shows the construction of the garage slab in a similar (not mine) house. Rebar is in an approximately 12-inch grid. Never figured out what those deep reinforced troughs are for...

 

[rbrtmchl]

I used a Bosch SDS drill bit made for drilling into masonry with rebar. Here is a link.

https://www.lowes.com/pd/Bosch-Bull...sonry-Drill-Bit-for-SDS-Plus-Drill/1001066524

 

[rlitman]

I used a Bosch SDS drill bit made for drilling into masonry with rebar. Here is a link.

https://www.lowes.com/pd/Bosch-Bull...sonry-Drill-Bit-for-SDS-Plus-Drill/1001066524

Yep. The 4 cutters don't get fazed by rebar. In smaller sizes, I've seen the bits made with a solid carbide tip.

 

[artrem]

I have a Dewalt carbide SDS concrete bit and a Bosch RC2144 rebar cutter (link below).


https://www.lowes.com/pd/Bosch-12-in-High-Speed-Steel-Masonry-Drill-Bit-for-SDS-Plus-Drill/50429570


Would a 4 cutter do both and be a better choice for drilling anchor holes?

 

[lakeroadster]

Use epoxy anchors and you don't have to worry about the hole not being perfect

Not at all true. Oversized holes decrease the load capacity of the anchor.

 

[mike93lx]

Not at all true. Oversized holes decrease the load capacity of the anchor.

I didn't mean to imply a 1/2" hole is the same as a 1/4", but seriously, if it gets a little out of round, is there a real, practical difference?

 

[ConCretin]

Thanks guys for all the comments. I was just wondering if when the bit encounters rebar it just stops, or if there was danger of the bit catching and twisting the drill, messing up the hole and possibly my wrist.

Actually it's more like the bit stops advancing. You'll be drilling along nicely with the bit advancing at a slow but steady rate. Your mind will wander with the shear boredom and pain of it all when it suddenly occurs to you that progress has stopped. The bit continues to turn but you aren't getting anywhere. You've hit rebar! It's not all that traumatic really.

Btw, A carbide drill bit requires a hammer drill while a rebar eater requires a standard drill. Use the former until you hit steel and then switch til you saw through it.

 

[Buckgnarly]

Actually it's more like the bit stops advancing. You'll be drilling along nicely with the bit advancing at a slow but steady rate. Your mind will wander with the shear boredom and pain of it all when it suddenly occurs to you that progress has stopped. The bit continues to turn but you aren't getting anywhere. You've hit rebar! It's not all that traumatic really.

Btw, A carbide drill bit requires a hammer drill while a rebar eater requires a standard drill. Use the former until you hit steel and then switch til you saw through it.

100% this and my experience.

The bit just stops, and when I pulled it up there metal flakes stuck to the bit. Confirmed with flashlight, ordered the rebar cutter from Amazon and 2 days and about 30 sec with my M!8 drill I was back in business.

 

[lakeroadster]

Use epoxy anchors and you don't have to worry about the hole not being perfect

Not at all true. Oversized holes decrease the load capacity of the anchor.

I didn't mean to imply a 1/2" hole is the same as a 1/4", but seriously, if it gets a little out of round, is there a real, practical difference?

It depends on what you define as "a little"...

Anchoring Systems General Instructions for the Installer

 

[Kev-o]

installed my maxjax not long ago and hit rebar. just buy a bosch bulldog extreme carbide tipped bit. this will drill all of your holes. i also purchased the bauer demo hammer/drill combo (the one that retails for $100). i only needed it to do this job and to rent one from home depot was $50 or so. if i want to move the lift the drill is paid for...LOL. It did the job so quick. when you hit rebar you make slower progress, but i would say 45sec to 1 min/ hole with rebar and 30-45sec without rebar down to their 5" deep that they want.

 

[artrem]

Actually it's more like the bit stops advancing. You'll be drilling along nicely with the bit advancing at a slow but steady rate. Your mind will wander with the shear boredom and pain of it all when it suddenly occurs to you that progress has stopped. The bit continues to turn but you aren't getting anywhere. You've hit rebar! It's not all that traumatic really.

Btw, A carbide drill bit requires a hammer drill while a rebar eater requires a standard drill. Use the former until you hit steel and then switch til you saw through it.

Thanks! This is exactly the kind of information I was looking for.

 

[MileHighRover]

installed my maxjax not long ago and hit rebar. just buy a bosch bulldog extreme carbide tipped bit. this will drill all of your holes. i also purchased the bauer demo hammer/drill combo (the one that retails for $100). i only needed it to do this job and to rent one from home depot was $50 or so. if i want to move the lift the drill is paid for...LOL. It did the job so quick. when you hit rebar you make slower progress, but i would say 45sec to 1 min/ hole with rebar and 30-45sec without rebar down to their 5" deep that they want.

That's the same setup I had. Even bought the same Bauer just for the job.

When I hit rebar I just switched the tool to drill, went through the rebar, then switched back to hammer drill and kept going.

 

[FTG-05]

^ This.


NVM. I missed it.

 

[Kevin54]

wow will be mounting an air compressor to the floor this week, i hope i don't hit rebar

Why mount it to the floor? Set it on rubber pads and it won't go anywhere. We set all sorts of machinery at work on rubber isolation pads and never bolted anything. My compressor has been sitting on rubber pads for years now and has never walked.

But if you are insistent on bolting it down.....put some sort of isolation pad between the feet and concrete.

 

[artrem]

Drilled and installed the anchors for one post yesterday. I had a more difficult time than my previous install. In three of the holes, the bit hit something causing it to bind. Fortunately my Dewalt hammer drill has a clutch. Not sure if it was rebar or aggregate. The rebar cutter took care of it but I later found that the masonry bit would power through if I backed off a bit. A little over 4-1/2 inches for most and a little over 5 inches for the first hole.

All the anchors set properly and after installing the column, tightening the bolts to 95 ft-lbs, I removed the post and inspected the anchors. All set at 1/8" or a little below, except the first one. That one set just at the top of the hole. The drill caught and wobbled to the side on that one and it must have made the hole a bit out of round.

Normally, I'd drive it out through the bottom and get an epoxy anchor. Unfortunately, this is the only hole I didn't drill all the way through. So I thought I'd try to pull it out by setting the sacrificial bolt through a 1-1/8" socket over the anchor and torquing the bolt. I tightened the bolt to 100 ft-lbs and the anchor didn't budge. So now I'm trying to decide if it's worth the effort to try and punch it out through probably 1/4" or less of concrete at the bottom, or just use it as-is since it seems to be set.

 

[Copymutt]

Thanks guys for all the comments. I was just wondering if when the bit encounters rebar it just stops, or if there was danger of the bit catching and twisting the drill, messing up the hole and possibly my wrist. The bit I have was only used to drill the 10 holes in the previous install and the rebar cutter is brand new.


The photo shows the construction of the garage slab in a similar (not mine) house. Rebar is in an approximately 12-inch grid. Never figured out what those deep reinforced troughs are for...

The thick pours are used instead of a complete footer where a load bearing wall is scheduled.
Jim

 

[artrem]

The thick pours are used instead of a complete footer where a load bearing wall is scheduled.
Jim

Jim- That makes good sense. But there are no load bearing walls or supports inside the garage, nor are there any on the builder's option sheet. I found a photo of my 3-car garage under construction and you can see the same two troughs in the pour. I'm guessing they are there for added support of the slab?

Drilled the next 5 holes for the other post. Tough going. This time I hit rebar in two of the holes, as well as hard areas, maybe aggregate. The rebar cutter did the trick but it took a good 5 minutes of drilling to cut through the rebar. But holes are done. This time I drilled all the way through the slab, but they have rock underneath so I don't think I can drive the anchors out through the bottom anyway. Procrastinating on bolting the second column; trying to decide if I want to go epoxy or trust the wedge anchors. I've used the Wej-it anhors before with no issues but with all the trouble I had drilling these holes, I worry that the tolerances aren't as close as they could be.

 

[wssix99]

I found a photo of my 3-car garage under construction and you can see the same two troughs in the pour. I'm guessing they are there for added support of the slab?

They wouldn't be there for the slab. Was there any additional steel inside them? Are there beams above them in the ceiling? They could be there to act as grade beams or tie backs to "hold back" the foundation wall on the right from bulging out into your basement to the side of the garage.

 

[artrem]

They wouldn't be there for the slab. Was there any additional steel inside them? Are there beams above them in the ceiling? They could be there to act as grade beams or tie backs to "hold back" the foundation wall on the right from bulging out into your basement to the side of the garage.

There is extra rebar in those troughs. There are no walls or other load bearing structures on the slab. When they build these houses they first dig the basement which includes the garage space. They then put the concrete forms around the perimeter of the pit and on all 4 sides of the space where the garage will be built. Once the forms are removed, they fill in the garage space and pour the slab. Seems an odd way to build a house, but it does provide 9-ft of support to the edges of the garage floor. So this is why I wondered if those troughs are there to add support to the garage slab which is poured over fill dirt.


FWIW, I posed this question to the construction supervisor here. If I get an answer I'll post it.

 

[wssix99]

FWIW, I posed this question to the construction supervisor here. If I get an answer I'll post it.

Maybe it would describe what they are on the plans.

There is extra rebar in those troughs.

Do you have a picture of that?

Seems an odd way to build a house, but it does provide 9-ft of support to the edges of the garage floor. So this is why I wondered if those troughs are there to add support to the garage slab which is poured over fill dirt.

It's not there for the floor. The dirt below and sub-base supports the floor. It's likely there to tie back the foundation walls at the ends of those grade beams or its there to add structure for what is above. (Sometimes, there will be a beam above, the grade beam under the slab, and then two columns at the end; making a structural rectangle, which in this case cars could drive through.)

 

[artrem]

Maybe it would describe what they are on the plans.

Do you have a picture of that?

It's not there for the floor. The dirt below and sub-base supports the floor. It's likely there to tie back the foundation walls at the ends of those grade beams or its there to add structure for what is above. (Sometimes, there will be a beam above, the grade beam under the slab, and then two columns at the end; making a structural rectangle, which in this case cars could drive through.)

You're right, see cropped portion of plan. These troughs are referred to as "reinforced grade beams", whatever that is.

Getting back to the Maxjax install, all the anchors went in well although one on each column set close to the top of the holes. However, I haven't tested them because unfortunately, it seems that the seals have failed in one of the hydraulic cylinders. I was able to pre-order a replacement from BendPak but it won't ship until sometime in August