Something like this?
LayOut won’t dimension to section cut lines because they aren’t “real” edges like those you draw in the model. There are a couple of options for dealing with that, though. Either turn off the section plane temporarily and update the scene, add the dimensions, and then turn the section plane back on, update the scene and style again and update the reference (which is what I did) or you could use a Group From Slice and dimension to that. The downside of this second option is that the dimensions aren’t linked to the foundation, they are linked to a different group. If you have some reason to modify the foundation walls, you must remember to modify the group from slice, too, or the dimensions won’t be correct.
By the way, I notice you have the scene modified in LayOut. This is not good practice because it breaks the link from the scene in SketchUp. It’s best to avoid doing anything in LayOut that makes the scenes show as modified.
In SketchUp I see you are not using layers correctly. All raw geometry (edges and faces should have the Layer 0 tag. Only groups and components should get other layer tags.