Acesalad

I am trying to recreate a house to show how it would look updated.  It is a Cape with a shed dormer.  I followed the knowledge base article on creating a shed dormer, but as you can see in the picture, the back wall of the shed dormer is a continuation of the first floor back wall and in my design the walls are separate.  I cannot figure out how to make these the same wall.  I am using Home Designer Pro 2019.

Thank you solver.  This seemed to work although I got the "This operation modifies one or more automatically generated walls. The walls(s) will be retained and will not regenerate automatically. Would you like to continue with the operation?" message.  I did not think to go up to the Attic level and stretch the walls.  I also took your advice on my signature.  Thanks again!

I was doing the Basic Roof training webinar and in the part where he designs the Shed style dormer, I followed the instructors directions but I still get a gap in the walls.  Attached is a picture of my screen.  Does anyone know how to eliminate these gaps?