Hi, I’m quite new to Dynamo, made the following to create some rooms surrounded by walls having fire rating of 1. I know it doesn’t do that, but creates some rooms which have zero area. Does anybody know why it is like this? Also any help to create the room surrounded by walls with fire rating of 1?
Thanks 
If the room after it has been created is not bounded by walls or boundary lines then the area of these rooms would be 0.
You need to create the boundary elements such as walls or Room Boundary lines first. Then create a room at the same level and point inside then these new rooms will report an area.
Try test the workflow in Revit first before doing it via dynamo it might help pick up these errors.
Edit: Check out this great FREE YouTube course in Dynamo to help you progress your learning.