What is your experience with Hambro?
How are the stair openings supported, are additional columns and beams typically required for this?

How about soundproofing so noise doesn't pass across the rooms through the ceiling drywall?

I'm also hoping to be able to put in curbless showers which will require a 2" drop in the floor surface. For a 4" slab thickness that doesn't sound feasible. Has anbody seen this being done and if so how?

I had one project planned and engineered with Hambro, then unfortunately the project fell through. Working with Hambro was excellent; they had provided detailed working drawings specific to the ICF project which was nice. I've seen a number of installed Hambro projects; I didn't hear any complaints, they all had in-floor radiant heating, although I didn't think the slab was 4" thick? Possibly shorter spans. Just inquire direct with them if the drop pan in the shower area is possible. From a sound point of view, both owners said it functioned well (one was drop ceiling, one was drywall). I think they used a sound batt insulation above the drywall, not sure about the ceiling tile one. The mechanical and electrical guys liked it - no valence boxes and lots of access for mounting their "stuff". Ends up as a thicker overall floor height due to the OWSJ concept, keep that in mind. Good luck!

Forgot: The stairs were completely open - no posts. They engineered it with integrated steel beams. Not sure if Hambro did this or the project engineer, but the base of the stairs was completely clear and open with no posts (really opened up the space).

Jake - thanks for the feedback.

If anyone had it in their homes I would also be very interested to hear any pros and cons.

We are just starting a large residential job with 10'6" Nudura walls and Hambro floors. Basement and main floor. The second Hambro acts as a ceiling.

Slab thickness on Hambro will vary with span. The slab thickness is integral to the design so you have to let them know if you want to drop part of it of the shower.

The ceiling drywall cannot be directly attached to the bottom chord. It must be suspended to level it. The joists are all pre cambered and the weight of the concrete takes most of this out but there is no guarantee that the bottom chords will be in plane. Suspending it also decouples it from a sound perspective.