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JetMech642 09-22-2011 12:40 PM

Edge Distance for Drilling into Concrete
I will be installing four vinyl porch posts on an existing concrete slab that is 4" thick. The tapcon concrete screws I will be using are 1/4" x 2 1/4". How close can I get to the edge of the concrete without worrying about cracking the concrete?

sixeightten 09-22-2011 12:53 PM

I would tr yto stay at least 4 inches away. Only drill as deep as you need to. They make tapcons that are shorter.

AGWhitehouse 09-22-2011 01:10 PM

I agree with 4". We have gone as close as 3" with some designs, but unless you can ensure the concrete mix is strong enough I'd stick with 4".

TrapperL 09-22-2011 06:00 PM

We drill these things weekly and the installation calls for the post to be at the edge of the slab. We drill at 1 1/4" away from the edge. I've never had a slab break in the last decade or so.

Mr Chips 09-22-2011 07:50 PM

With Concrete Screws you want to maintain an edge distance of at least 6 anchor diameters, but keep in mind your tension and shear values are greatly reduced when you are this close. You need to be at least 12d from an edge to get full tension and shear

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