RH Testing Thick Slabs

[CC Solutions]

Being that slabs dry to the top, you could drill down until you hit a point that exceeds the maximum level of RH and stop there.

I'm just saying it is easy to drill to 4" and check what you have. If it is too high, it will only get higher as you drill further down.

If you want to remove the top few inches of concrete to get your sensor down 6" I can't see how that would affect a short term reading.