# Edge Distance for Drilling into Concrete



## JetMech642 (Aug 5, 2011)

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?


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## sixeightten (Feb 10, 2009)

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


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## AGWhitehouse (Jul 1, 2011)

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".


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## TrapperL (Jul 23, 2011)

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.


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## Mr Chips (Mar 23, 2008)

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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