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For fixing a 2 inch screw on concrete wall, how should I drill for good strength and no damage to the wall. I tried a 2 inch screw and drilled for 1 1/2 inch and later tried to screw it into the hole. But the problem I faced is that after the end of the screwing step, a circular portion came out of the wall wall and it became a very big hole.

Now how to fix this?

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How big is the very big hole? –  sharptooth May 29 '13 at 14:50
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2 Answers 2

You should drill the hole at least 1/4" deeper then the screw depth. Also make sure to blow out all of the dust from the hole once you are done drilling.

If you use a concrete screw like a Tapcon you don't need to deal with plugs or expansion bolts.

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I'm not sure I can agree about the 1/4" minimum, but clearly the hole should be at least slightly deeper than the screw length, otherwise the screw will simply not go any deeper than the hole bottom. –  sharptooth May 29 '13 at 14:50
    
1/4 is recommended by manufacturer. Very hard concrete screws are very brittle, also. This class of screws will over torque and BREAK if they bottom out. –  HerrBag May 29 '13 at 16:21
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A lot of variables there to make a proper answer:

Basic tenet of concrete use: Compression = good, tension = bad

  • Wall thickness

    Drilling to half the wall depth for a threaded fastener (with extra room as Steven suggests) is the safest for embedding fasteners without stressing the wall itself.
    The screw point greatly magnifies the force at the tip, causing tension outward (bad). Sometimes a through hole, with threaded rod, thrust washers and nuts, is a better solution (puts concrete in compression (good)).

  • Age of concrete, quality of concrete

    The older concrete gets, the stronger it gets (if allowed exposure to moisture). Poorly formed concrete (too much water, too little water, too low a percentage of Portland cement) will mean spalling (surface chipping), cracking.

  • Fastener weight bearing requirement

    This question addressed the weight range of various fasteners.

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