#6 rebar and engineering

The big heavy pieces are #6 rebar.  That is what I asked for after I decided to upgrade exterior to brick.  And that is what the engineer specified also, with a very nice box beam design.  Each beam has 4 pieces of #6 rebar running through it in a box configuration.  The ends are tied to the bent corner pieces of #6 shown.

In standard residential construction, #4 is said to be the heaviest used.  So that makes #6 industrial grade. I need that for 9 foot brick walls and the highly expansive clay soil (must be about the worst) that cracks foundations all over my neighborhood, and tosses the 5 foot deep 2 foot diameter concrete foundations of my Fencecrete fence around like matchsticks.

But I had also specified a 6" slab with #5 rebar.  The engineer decided on 4 inches with #3 rebar.  I'm not sure if Ronnie even gave the engineer my original specifications.  Now that the engineer has decided on #3 rebar for the slab, I really can't change that.  I'm not that kind of engineer.  I think it might have been better had I been talking to the engineer directly.  I could have asked for what I wanted, and he could have explained to me why, in this case, smaller might have been better.  Or he might have been willing to upgrade to #4 or #5 rebar for the slab "if I was willing to pay for it."  Which I was.

I complained to Ronnie about the 4 inch thickness, though, and he first agreed to up it to 5 inches.  Then I did some research which suggested that #3 rebar is commonly used even with 6 inch thick slabs.  So I asked Ronnie about that, and he said he had set the forms to allow a slab thickness of 5 1/2 to 6 inches since he was using 2x6's for the forms.

I found very interesting link that said that you needed to have a "control joint" every 2-3 feet for each one inch of slab thickness.  So 4 inches would necessitate a control joint in 8-12 feet.  For 5 inches it would be 10-15 feet.  For 6, 12-18 feet.  That is why I requested 6 inch thickness originally, so that no control joint would be needed comfortably in 15 feet.  It was also why I was strongly inclined not to go beyond 15 feet, and why I was also inclined to roll it back slightly to 14 feet 10 inches.

Now the forms have been moved away from the easement.  As yet only one 2x6 perimeter board is in place.  More about that later.

Maybe in future I'll see if I can talk to the engineer directly rather than having contractor as middleman.