In residential it is (I believe) a requirement to be stamped in the garage. The one I had stated: Warning post tension slab do not cut or core. It was placed within a foot or so of the garage door opening. Every home I've seen this is where it is located so there is no chance of it being covered...unless the owner is a pack rat.

That's good news as that is where I spend most of my time and have never seen one in the homes that I have owned in the past.

Thank you

Not a big deal.
That's why there are people who x-ray slabs.

I imagine that's expensive in other parts of the country where post tension is not popular but here its a dime a dozen.