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Old 06-18-2009, 11:39 PM   #1
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Drilling cinder block?


I want to add a 16" "wrought iron" fence to the top of a low cinder block wall along my driveway. The wall is filled and topped with red brick.

I could just use anchor bolts of some kind, but I know this fence will be leaned on etc. by neighbor kids, so I would like to sink the 'posts' through the brick cap and into the top of the wall several inches.

How can I drill a hole 1-1/2" or 2" in diameter into the top of this wall? Because it's not a 'through' hole I'm guessing there's no way to use a coring bit? I do have a small SDS rotary hammer, but even if a 1-1/2" bit is available it seems like too big a job for that.

I'm sure this is done every day by pros with the right tools, but how should I approach it?

Thanks...

Gary

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Old 06-19-2009, 12:00 AM   #2
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Drilling cinder block?


You can use a core bit,the center part will come out in one chunk.
Then shop vac the rest out of the hole.

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Old 06-19-2009, 04:23 PM   #3
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Drilling cinder block?


Quote:
Originally Posted by garyoutwest View Post
I want to add a 16" "wrought iron" fence to the top of a low cinder block wall....
How can I drill a hole 1-1/2" or 2" in diameter into the top of this wall? ........
That is really BIG wrought iron. Can you smaller material, like " ?



Quote:
Originally Posted by cincy plumber View Post
You can use a core bit,the center part will come out in one chunk.....
I don't see that, He wants to drill down into the top of the wall.
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Old 06-20-2009, 07:31 AM   #4
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Drilling cinder block?


What width is the cinder block? Guessing it's narrow if it's capped with brick? As CP says you can use a core bit, from above but you want to be dead centre front to back.

BUT also remember there are vertical ribs within the cinderblock reinforcing it so locate your hole accordingly. Narrow bricks often have two ribs in the middle section and one on each end, wider blocks generally have a center rib and one on each end

The other problem you will encounter from above is that this ribbing will be offset with each new row of block due to the staggered block pattern as you proceed down from above.

I would opt for a rod anchored right through to the ground on this one , otherwise the fence cap you are building will become a lever to dislodge the top of your short wall. Mark your cross ribbing on each block with a piece of tape and see if you can actually drill clean through from above in any area
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Old 06-20-2009, 10:42 AM   #5
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Drilling cinder block?


Hmm, you have a block wall capped with brick. Without pictures I have to imagine how this looks. If the bricks were laid perpendicular to the run of the block that would look fairly good. Now you are wanting to drill a hole through the brick, and in to the block, which you say "the block is filled". Does this mean with concrete? Let's just think this way for now. To core drill through the brick and on into the filled concrete will not be that hard with the proper equipment. For someone who has never used a good core drill with 1 1/2"--2" core dril-that's another story. Core drills are not monster, but they are like any specialty tool, they require a skilled operator and patience. I have, you can, core drill through the brick, on into the concrete block that has been back-filled. The core drill will go through the webs of the block. IF you get to the depth you want and you have not gone completely through the concrete-take a good size hammer, say at least a 2# and hit the cored part smack dab on top and center of the core drilled section. I have done this many times and the cored section will break loose at the bottom. Then comes the fun, getting the cored piece out. Drill into the cored piece, insert a Tapcon screw or something like that and pull it out. We have actuall done twelve inch (12") cores by twelve inches (12") deep this way. Insert your fence post, grout accordingly and keep the kids away, Good Luck, David
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Old 06-20-2009, 01:33 PM   #6
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Drilling cinder block?


Quote:
Originally Posted by garyoutwest View Post
I want to add a 16" "wrought iron" fence to the top of a low cinder block wall
One thing that no one has brought up yet is to ask how do you know that this is cinder block vs concrete block? There is a big difference in strength
http://www.us-concrete.com/products/masonry.asp

Another thing is how High is the block wall?

Another important thing that has already been asked is how wide is the Block? It is most likely 4, 6, or 8" block. This is an important question. . If its 4 block then it may be impractical.

When you say:
Quote:
Originally Posted by garyoutwest View Post
....The wall is filled and topped with red brick...
I infer that that the open cells in the block have been filled with grout. If that is correct, how do you know this because the wall is topped with red brick?

If the brick topping was added after the block was laid the grout IMO only has a 50-50 chance of extending down to the base. A common technique was to wad up some newspaper and jam it down in the top row of block then just trowel it off or add a row of bricks or some type of precast wall cap or stone.

A big consideration is whether or not the wall was built with a descent footing and vertical and horizontal Rebar
If the wall is 4 H or less, I would guess that you have <50-50 chance on the foundation/rebar issue.

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  • Driil a few test holes down about about halfway down the top row of block to check for grout filled cells. To make sure you are not just drilling into the block webbing, space some holes a couple of inches horizontaly.
You can buy a coring bit that has a centering drill
http://www.toolsforless.com/product/...entering_Drill
.:


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Last edited by PaliBob; 06-20-2009 at 01:40 PM. Reason: sp
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