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Community and Q&A

Using a powder actuated fastener in concrete block wall

NCJeff | Posted in General Questions on

I’m installing 2.5″ rigid EPS (BoraFoam brand) to the inside of my crawlspace walls which are concrete blocks.  I call them cinder block out of habit, but I guess the term is actually CMU.  Bought a Hilti DX460 Powder Actuated gun to drive the Hilti EPS fasteners into the blocks.  I’ve never used one of these guns before but was experimenting today trying to ensure I’m getting the correct penetration depth on the nail and have the power setting correct.  I’m using the yellow charges and 1st try set at setting 1, the nail didn’t fully penetrate and pulled right out.  2nd try the half of the block I was shooting into broke into many pieces, power at 3.  I backed it down to 2 and 3rd time seemed to be a charm with full penetration of the fastener into the block, but it also blew a big chip of the inside of the block into the cavity where the nail came through.  If I were in the crawlspace, I’d probably never know that was happening because it would be inside the wall.  Is that OK?  Am I supposed to be avoiding the cavity of the block and trying to hit the solid edges or even the mortar?  There’s not a lot of good instruction on this, even in the Hilti videos on youtube.  Any advice or experience is appreciated.

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  1. NCJeff | | #1

    Pictures of the nail damage inside and showing test pc of EPS attached to block from the front.

  2. Expert Member
    BILL WICHERS | | #2

    That's how it goes with these fasteners, and it's why I don't like them. I've installed thousands of them back when I was a datacomm installer. They're great in that they're fast, and they can go into concrete and even steel. They're not so great when someone calls the police thinking there is a shooter (yeah, that happened on a job once), but that's a different problem.

    You need to keep the gun perfectly perpindicular to the wall when driving the fastener. ANY angle and you're likely to have a blowout, or a ricochet. Over penetration is pretty common, since the charges aren't all perfectly identical, and neither is the composition of the wall you're shooting into. Blowouts on the backside are an unavoidable problem with block. You can minimize this issue by shooting into the block over the web between holes so that the block is more solid-like from the perspective of the fastener, but you still aren't guaranteed to avoid blowouts. I've had blocks fracture too, and end up with big, open hole I had to patch.

    Many years ago an electrician showed me tapcons and I've never gone back to powder actuated fasteners. Tapcons have their issues too, but in general they are far more predictable.


  3. GBA Editor
    Martin Holladay | | #3

    You probably want to read this article: "Fasteners for Concrete and Brick."

  4. ohioandy | | #4

    Wrong tool for the job. Go with a hammer drill and a box of Plasti-Grips (made by Rodenhouse, available at big box or online.) These plastic anchors are not cheap, but they work like a charm; you only need a few per sheet depending on conditions. Tapcons work too, are cheaper but more fuss.

  5. user-5946022 | | #5

    Don't damage your block like that.

  6. firutaarnold | | #6

    Judging by the photos, everything is not going smoothly there. Perhaps you can contact specialists from I think these experts on laying stone foundations and other construction issues will be able to help you get rid of your problem. I don't understand the construction and laying of concrete or stones, so I never do it myself. I'm surprised at how many people try to cope with this themselves. Maybe you'll make even more mistakes than before when you try to do all this using guides from the Internet. It's better to trust those who make fasteners better than yours. It's just my personal opinion. Good luck.

    1. Expert Member
      BILL WICHERS | | #7

      Seems to be quite the uptick in spam as of late.


      1. DC_Contrarian_ | | #8

        I was hoping that forcing everyone to re-register would slow it but no such luck.

        1. kbentley57 | | #9

          Does it seem like those are written by a person rather than an AI? I’m not sure whether to be impressed or worried.

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