The proverbial wise man bldng on a rock
My concrete contractor just bailed on me! Took one look at my site conditions and made a graceful exit. I can’t blame him honestly but since, quite possibly, I am going to be forming my slab on my own now, I need some info.
The main concern is that I’m on a rocky site. By rocky I mean a solid slab of limestone several feet thick under about 6″ to 8″ of loose, flat boulders and dirt. I had a backhoe operator dig my grade beams and he snapped a tooth on his bucket first pull. This is some pretty hard stuff.
I can’t see digging out rock and replacing it with softer concrete so there is no real need to go deeper than the top of the slab rock. I’ve swept some of the bottoms of my grade beam trenches with a broom and the slab is virtually seamless. My engineer has assured me that my slab design will be far more than adequate in these conditions. Even with just 6″ to 8″ grade beams.
Here is the problem. How do I secure my forms? I bought a bunch of 18″x 3/4″ steel pins to set my batter boards but I was bending them trying to drive them into the rock. I bought a long chisel for my air hammer and made some progress by pre-punching the holes but it’s slow going. I am considering pre-drilling with a rotary hammer and a long 5/8″ diamond core bit then driving the pins into the holes but I would think it would be hard to fudge them back and forth as I’m tweaking the forms into alignment. (shims maybe?) Not to mention expensive on my rent-a-tool budget since I will be doing this little by little on evenings and weekends. At any rate, my limited forming experience using 2×4 support stakes ain’t gonna help me here.
I’m really stumped on this one. I’ve never had to deal with site conditions quite this rough before. At least the view is worth it- I think. I appreciate any suggestions.
“The hard stuff we do right away- the impossible just takes a little longer” -Sign above the counter at a custom fab shop-