question about expandiing the hull

So I want to expand my hull.  I made some sort of "outline" of where I wanted it built, then used the building menu and managed to turn the design into yellow squares.  Does this mean it's queued?  When will the colonists start building it?  Also, how do I access the new area once built?  I saw several door designs but am not sure how to replace existing walls/hull with a door.  Thanks!

When the build outline is yellow it is queued so should start building when a pod and crew member are available.  To build a internal door you have to place it as you would a wall section, you cannot replace a wall with a door without first removing the wall in my experience

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