Stupid Mistake 109: Concrete is Hard!

Pete Nolan Jul 3, 2008

  1. Pete Nolan

    Pete Nolan TrainBoard Supporter

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    Yesterday I started a project that required me to to anchor a 2 x 6 base plate to the concrete floor of my porch. I still had the .22 powered nail gun from splitting the garage in 2002, nails, and the highest powered cartridges, something akin to a .22 long rifle.

    I remembered splitting a garage in 1972 for my first model railroad and woodworking shop. I drove the stout fluted nails through a 2 x 4 with a small sledge hammer. It took a lot of patience, and once I hit a nail one times too many, which sprung the nail completely loose. By the way, N-scale model railroading and woodworking shops do not mix well.

    I remembered splitting a garage in 1982, again with stout nails and that same small sledge. This time I built the wall first, applied a thick coating of Liquid Nails to a chalk line on the floor, wedged the wall into place, and started banging patiently. No sweat!

    Then I remembered splitting the garage in 2002, for my current train room. Yep, I built the wall first, applied a monstrous bead of glue, and wedged the wall in place. It was quite a proud construction feat, as this floor sloped four inches along its 24 feet. Again, I took my trusty little sledge and started banging.

    I took my trusty sledge and hit the first nail much harder.

    I took my trusty sledge and hit that dang nail as hard as I could!

    Nothing. Despite the tack of the glue, I could still move the base plate. The nail hadn't penetrated one iota of concrete. Maybe I was trying to drive into a rock?

    I tried a second nail a few inches away. After a dozen increasingly forceful blows, the nail still hadn't pierced the concrete. Another rock? I wondered.

    No, stupid! The day you poured the slab it was cold, remember? It was going to freeze overnight. You specified a 6000-pound/inch mixture instead of the regular 3000-pound mixture!

    OK, down to Lowe's for a .22 caliber nail gun. And not the green loads, nor the yellow loads, but the red loads. Nail guns, like printers, are cheap; but the loads and nails will get you. So I bought a dozen.

    OK, eye protection on. Load the gun, lean on it, and pull the trigger.

    WHAM!

    Ouch! Despite my weight, the gun instantly and violently jumped at least six inches, throwing me harshly up and backwards.

    What's that you say about ear protection? I can't hear you!

    The 2 inch nail penetrated perhaps a quarter inch into the concrete through the 1 1/2 inch plate, as it still stuck up 1/4 inch.

    Maybe I should lean on it harder? And why are the church bells ringing?

    I found some earplugs, and put my full weight on the second shot.

    WHAM!

    Holy moly! The gun still jumped at least three inches, and there was the nail, still penetrating only a quarter inch, but this time bent at a weird angle.

    OK, let's stop and figure this out. How many nails do I really need? Won't the glue hold it well enough? Maybe the ends will hold it? OK, one more . . .

    WHAM!

    And the whole base plate is loose again! The third shot didn't penetrate at all, and loosened the other two!

    WHAM! WHAM! WHAM! Six shots later I had it more or less anchored, hoping the glue would not only keep out ants, which was its primary purpose, but hold the wall.

    Back to yesterday. I know enough that I have to stand on the plate. Eye and ear protection OK. Load and fire.

    WHAM!

    No bounce at all from the gun. The nail goes completely through the plate! Huh? Oh yeah, I poured the porch later. It's regular concrete. I went down and bought the green loads.
     
  2. HemiAdda2d

    HemiAdda2d Staff Member TrainBoard Supporter

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    Good grief--this almost sounds like an episode of Home Improvement, with Tim Allen's typical antics on the Tool Time show...
    Thanks for the laugh....:D:D
     
  3. Siskiyou

    Siskiyou In Memoriam

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    Pete, obviously, you didn't have the right supervision. ("Shouldn't you ask someone how to do that?" "Are you sure you're holding that right?" "Shouldn't you be drilling holes first?" "Are you using the right ones?" "I said, 'shouldn't you be using ear protection?'")
     
  4. David R

    David R TrainBoard Member

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    Wouldn't it be better/easier to drill a hole and use a sleeve anchor or dynabolt (not sure what you guys call them over there, but one of these things) than trying to hammer/fire nails into the concrete??
    I've worked as a builder, and for a company that sells fastenings, and been a driver for a building supplies company, so I've been around construction a fair bit and I've never seen a frame being nailed to a concrete slab before. Is that a standard practise in the US??

    [not being critical or anything, just curious!]
     
  5. r_i_straw

    r_i_straw Mostly N Scale Staff Member

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    I have been told that nailing wall plates into concrete works better if the slab is relatively new and has not totally cured. When we built my parents house we used "L" bolts cast into the slab for the outer walls. Drilled holes in the plate to slide over the bolts and secured with washers and nuts. For interior walls we used the 22 caliber nail gun. Never tried it on "old" concrete before. Have used drill and anchors at times though.
     
  6. Cleggie

    Cleggie TrainBoard Member

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    :giggle7yc:LOL, That's funny Pete.

    Now, I'm going to send the occupational health and safety people around to your house, OK? Who knows what other dodgy practices they may find.:tb-wink:
     
  7. Hytec

    Hytec TrainBoard Member

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    Uh Pete, have you considered using a 3/8" or 1/2" hammer drill? Drill holes through the sill and into the concrete. Insert expansion anchors through sill into the holes in concrete and either a) strike with hammer to set sill tightly against floor, or b) tighten nut on expansion stud drawing sill tightly against floor. In either case you will have anchored the wall to the concrete with enough rigidity to withstand a Category III hurricane....assuming you have installed a sufficient quantity of anchors, say one every 12-16 inches

    Trust me, expansion anchors work remarkably well, well enough so that the full might of Hurricane Katrina was unable to dislodge a 12' diameter 8' high roofed redwood gazebo secured to a concrete pool deck with sixteen 1/4" expansion anchors. And I didn't even work a sweat drilling the sixteen holes...:tb-biggrin:
     
  8. jeffrey-wimberly

    jeffrey-wimberly TrainBoard Member

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    Thanks for the laugh Pete. You reminded me of the kind of hard work my father and I put in on the bunkhouse over at the cow pasture. We didn't have nail guns back then, just the sledge hammer.
     
  9. Phil Olmsted

    Phil Olmsted TrainBoard Member

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    Ken, please don't sic OSHA on Pete. We may never hear from him again. I'm not sure the federal prison system allows internet access.
     
  10. porkypine52

    porkypine52 TrainBoard Member

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    YUP! Had about the same deal with a powered nailer several years ago. Was trying to put bottom floor plates on basement floor for several dividing walls. *#@+# nails kept twisting, bouncing and bending. Went and got larger loads, with the same results. Finally went to the dealer that sold the power nail gun to get the BIG LOADS. Dealer said he could not sell me the high power loads because you now have to have a LICENSE to use the high powered/big loads. Just too many accidents with untrained/unlicensed users. Dealer asked me to describe exactly what I wanted the big loads for. I told him the story and he stated that the concrete in our basement most likely had reached it's hardest set. NOTHING I could buy/use would be able to penetrate the hardened concrete. House was built in the mid-1950's. Dealer said to either HIRE a contractor to lay the bottom plates($$$ YIKES!!) or get an impact/hammer drill and use anchors. Went an borrowed a BOSCH Bulldog hammer drill and got the job done. The Bulldog drills through concrete like a regular drill goes through pine!
     
  11. HemiAdda2d

    HemiAdda2d Staff Member TrainBoard Supporter

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    Those hammer drills are sweet, aren't they? We have one at work. I had to drill a 3/4" hole, and that thing drilled so fast that the depth stop halted me what seemed like 5 seconds after I started!
     
  12. Mike Sheridan

    Mike Sheridan TrainBoard Member

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    About 25 years ago I hired one to put anchors in concrete. I then went and bought my own (a professional grade 'pneumatic hammer' job - they didn't make consumer ones back then).
    I still have it (used it a few days ago) and it it is still one of the best buys I've ever made :)


    Takes about 28 days for normal concrete to reach most of it's full strength (varies with temperature) and it needs to be kept damp throughout that time.
     
  13. Malta Guy

    Malta Guy TrainBoard Member

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    You didn't have supervision..!
     
  14. Pete Nolan

    Pete Nolan TrainBoard Supporter

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    Yep, probably should have gotten a hammer drill. I'll have to borrow one and see how it drills through this 6000-lb stuff. We use that strength concrete at work to simulate granite.
     

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