drilling into concrete - 2 layers?

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benevo
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drilling into concrete - 2 layers?

Post by benevo » Wed Jan 02, 2019 3:22 pm

Hello Bogleheads, and Happy New Year!!

We have an older (early 40s) home. In our unfinished basement, we use it for laundry and a home gym. I was looking to hang a TV on the concrete wall, and have the right screws and anchors. Upon drilling the holes, however, which are probably about 3" deep, the drill once it gets to about 1-1.5" in, suddenly goes straight in. I freak out a little, at first thinking how could this wall (the other side is the garage) be so thin? I look around in the garage though and the hole didn't go through. Upon closer inspection, it seems like there are 2 layers of concrete/brick with a gap in-between. Is this normal? A few people I asked had never heard of this, but granted they aren't pros in this area either!

Basically, 2 questions:
1. What's the purpose of this?
2. How can I hang an anchor/screw/TV if the anchor will now go into the open gap/not work the right way? Am I out of luck, or is there some sort of fix that would allow me to still use the anchors/screws and hang the TV?

For reference, here's a very poor example of what I think it looks like - note, the gap in-between the two layers is probably an inch, maybe 2 if that? Hard to tell, since I'm looking in the hole of a 1/2" drill. :)

Image

THANKS for any advice!
-be

Shallowpockets
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Re: drilling into concrete - 2 layers?

Post by Shallowpockets » Wed Jan 02, 2019 3:42 pm

If you had had a depth stop on your drill you would not have punched through. Then you would have used the anchors anyway. Now you know there is a space back there, no matter. I would use the anchors you bought.

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mhadden1
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Re: drilling into concrete - 2 layers?

Post by mhadden1 » Wed Jan 02, 2019 3:54 pm

An anchor in 1.5 inches of concrete should be fine for holding things like non-CRT televisions.
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Topic Author
benevo
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Re: drilling into concrete - 2 layers?

Post by benevo » Wed Jan 02, 2019 3:56 pm

mhadden1 wrote:
Wed Jan 02, 2019 3:54 pm
An anchor in 1.5 inches of concrete should be fine for holding things like non-CRT televisions.
Thanks! Even if it's sitting in front of the gap/if it were pushed back would fall into the gap?

craimund
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Re: drilling into concrete - 2 layers?

Post by craimund » Wed Jan 02, 2019 3:56 pm

You should be able to anchor sufficiently in the inner layer to hold up a TV. Try to get anchors of about the same depth as the thickness of this layer.

I would be surprised if the layer was only 1-1.5 inches thick. Bricks are thicker than that (2.5"). Are you sure you're not in the void of a cinder block? That would make more sense.
"When you ain't got nothing, you got nothing to lose"-Bob Dylan 1965. "When you think that you've lost everything, you find out you can always lose a little more"-Dylan 1997

euroswiss
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Re: drilling into concrete - 2 layers?

Post by euroswiss » Wed Jan 02, 2019 4:02 pm

You may be dealing with a cinder block wall. If so, you can use a short concrete anchor (for example: https://m.youtube.com/watch?v=5006AqQ9Slw ), or even a drywall type anchor (like so: https://www.amazon.com/gp/product/B072J ... 6HEFFXK4PX ), that reaches into the hollow space.

barnaclebob
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Re: drilling into concrete - 2 layers?

Post by barnaclebob » Wed Jan 02, 2019 4:39 pm

I'm betting its a cinder block wall.

If so, I'd probably go the toggle bolt route. However, if you haven't drilled all the holes, its possible not all of your holes will hit a hollow space on the wall if it is cinder blocks.
Last edited by barnaclebob on Wed Jan 02, 2019 4:41 pm, edited 1 time in total.

researcher
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Re: drilling into concrete - 2 layers?

Post by researcher » Wed Jan 02, 2019 4:41 pm

benevo wrote:
Wed Jan 02, 2019 3:22 pm
I was looking to hang a TV on the concrete wall, and have the right screws and anchors. Upon drilling the holes, however, which are probably about 3" deep, the drill once it gets to about 1-1.5" in, suddenly goes straight in.
Upon closer inspection, it seems like there are 2 layers of concrete/brick with a gap in-between.

Basically, 2 questions:
1. What's the purpose of this?
2. How can I hang an anchor/screw/TV if the anchor will now go into the open gap/not work the right way? Am I out of luck, or is there some sort of fix that would allow me to still use the anchors/screws and hang the TV?
Do you have a solid monolithic concrete wall? Or do you have concrete block/cinder block wall?
As a previous poster mentioned, it sounds like you have a concrete block wall.

What type of screws/anchors do you have?
Most should be good for both solid concrete walls and concrete block walls.

Topic Author
benevo
Posts: 127
Joined: Wed Apr 05, 2017 7:21 am

Re: drilling into concrete - 2 layers?

Post by benevo » Wed Jan 02, 2019 4:47 pm

Thanks, all! All great info and responses - sounds like toggle bolts will solve this issue. As always, Bogleheads are my go-to for all sorts of knowledge! :)

adamthesmythe
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Re: drilling into concrete - 2 layers?

Post by adamthesmythe » Wed Jan 02, 2019 7:35 pm

barnaclebob wrote:
Wed Jan 02, 2019 4:39 pm
I'm betting its a cinder block wall.
You mean concrete block. The 1.5 inch thickness is about right.

If it was me, I would drill all the way through and use expansion-type anchors.

TVs don't weigh much these days and the forces applied to the wall will mostly be in the vertical direction, not tending to pull the anchor out of the wall. Unless you plan to cantilever out a considerable distance.

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