So keep in mind this waffle slab has been designed by an engineer and based that design off of the geotechnical information which tells them the type of soil the expansion and such.

So if you look at the details of the foundation you have the post tension cables, generally you’ll have a rebar in the corners, this particular slab has two cables, in the bottom and one cable on top. So let’s talk about the cables, the cables themselves are about half inch stranded cables. You have a dead end here, what that is is where the pull starts and then you have a live end here. The reason they call that a live in is this thing that they hook up the apparatus that pulls that cable to pull tension across the cable so from one end to the next they’re squeezing that foundation together.

The amount of tension on these cables I believe is around 33,000 pounds, so they’re going to take this half inch cable and they’re going to stretch it about a foot and a half. That’s how much tension is pulling these slabs to pull them together. Again it’s all based on a geotechnical information that the engineer used to design this foundation.