Yes, as @DaveR replied, the way to set it up is usually within SketchUp. you Model what is going to be in the model. Modeling the slab doesn’t give any problems, but modeling the rebar is a different ballgame, it can bloat the file with a lot of polygons and edges.
If you do wanna go this route, be sure to set the ‘sides’ to a lower (8 or 6) count after choosing the circle tool or arc.
Here, I use Profilebuilder to make a foundation:
Though, in most rebar drawings, a much simpler, almost symbolic drawing is more common:
I use this model to get the outline of the concrete, and so I set up a scene in SketchUp, save the file and send it to LayOut.
I draw the outline of the insulation as a scaled drawing (same as the viewport is set to) and then draw the rebar as simple linestrokes:
Again, with the scaled drawing, you don’t have recalculate to scale, you would just type the ‘real world’ dimensions
here the file:rebar.skp (236.7 KB)