New home construction question

[Nevada Carrier]

Hello,

This is my first post here. I am a Computer Engineering Student at UNLV. I came here to ask about some topics relevant to the construction of my new home. Last Friday, the post-tension slab was poured, but today, the framers began erecting the rough framework. My question has to to the the stressing of the post-tension cables.

The general contractor advised me that this is typically done seven days after the pour, but only when the samples of the batch used pass a crush test. I was a bit concerned that they began framing before stressing the cables; this raises a number of "what-if" scenarios, that I'm sure you folks can imagine as well. To get to my question, Have they broken some structural engineering rules by building on a slab before stressing it? I read somewhere that stressing causes some kind of lift phenomenon with the slab. Perhaps I'm misunderstanding the process, but I would think you would not want to frame a house only to induce some movement under it. am I wrong?

 

[Trigger]

Is it a wood framed house? In general, contractors will frame the walls flat on the slab, and then raise them all on one day. It makes framing much easier, as they can snap lines on the slab and get everything flat, straight and level.

Now, I don't actually know what they should be doing, and I am only vaguely familiar with post tensioning. Post tensioning is done by casting sheathed bars into concrete and putting bearing plates on the ends of those bars. The contractor will then apply tension to those bars (I think it's either through hydraulic devices or by tightening large nuts on the ends - again, someone correct me if I am wrong, as I am not very familiar with the process) which puts the section into conmpression (through the action of the bearing plates). Putting initial compression load into the concrete will control cracking and deformation, and, if done correctly, can increase a member's ductility (check out Axial Force - Curvature diagrams, though those are more for columns and beams).

Wood frames are generally bolted into the concrete foundation using anchor bolts or hold downs. So I guess if they needed to, the contractor could always just pull the frames off of the slab if they are already bolted in. However, I believe for residential structures, so long as the concrete passed the slump tests on the day of the pour, the contractor will generally assume the concrete is good unless the cylinder compression tests come back as failures. If the cylinder tests come back bad, then it will probably have to be ripped out. But I wouldn't expect a contractor to wait a week before starting to frame a residential structure.

But I am by no means very experienced in this. Anyone else have better insight? I am curious about this too.