Core drilling question - minimum distance


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Old 10-23-20, 05:58 PM
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Core drilling question - minimum distance

I need to make a 3" diameter hole in my outbuilding's foundation. It's 10" thick, poured concrete with rebar reinforcement. Concrete is about 5 years old. I've recently wet cored through a 30 year old poured foundation for a water line, and the process went well.

What is the rule of thumb for minimum distance to the top edge of the foundation? I've been searching the web for calculations, or general best practice.

Thanks!
 
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Old 10-23-20, 08:04 PM
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I don't think there is a formula or rule of thumb.
I would think at least 3-4" from the top of the foundation would be ok.
Core drilling is non impact unlike hammer drilling which can crack if too close to the edge.
 
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Old 10-23-20, 08:59 PM
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Thanks. I was thinking at least a diameter of the bit away from the edge. This isnít a high-stress portion of the wall - nothing is bearing down on it directly from above where Iím drilling.

Unfortunately I expect to hit rebar on this core. I recall when the wall was poured he had a framework of rebar between the forms, would have to go back to my pics to see what it looked like. Iím hoping it cuts through it easily enough - I just need this second hole and the bit/drill will have paid for itself a second time around.
 
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Old 10-26-20, 07:13 AM
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I know Hilti makes a roto hammer bit that claims to cut rebar, Contact your banker for a loan before you get a price.

Most wet coring will cut rebar, just puts a lot of wear on the bit. Go slow and be careful to keep the bit wet.

Rebar is usually centered at 1/4 from the top and 1/4 from the bottom unless of course the plans state differently.
This is an approximation of what I have seen in my area. Your area could be way different.
 
 

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