First floor almost in.

Voila.

 Engineered wood. LVL (Laminated Veneer Lumber). Pressure treated wood and traditional lumber.
links: SolidStart, iLevel & Wikipedia.

On the left, SIPs is put in to form the exterior walls by the stair way.

On the right, a close up of LVL on top of pressure treated wood, sandwiching some sort of foam membrane and the concrete.

 

This area is where the stair well will be.

And there it is.