I decided to make the third floor fireplace the height of the wall.
I applied my wallpaper up to the fireplace line on both sides and then used a printed brick paper to cover the fireplace area. The fireplace area is as wide as the mantel.
I created a faux marble finish for the mantel and trim, like I did for the other fireplaces.
Everything else is covered with the brick paper. I even covered the side, floor and ceiling trim in brick paper. I used baseboard trim to create the side trim. When you cover any part with paper, the sides will show raw wood so I color matched the brick color with paint and painted the parts before applying the paper to them. That way you can not see raw wood anywhere.
Once the interior was finished, I was able to assemble the right side of the chimney exterior. This gives you the ability to finish the visible inside of the fireplace before it becomes inaccessible. You do not have to finish all the way up. Only about half way is visible through the fireplace opening.
Once that is done, you can complete the left side of the chimney exterior. At this point you have to reach through the rooms window to finish that left side. This side of the fireplace will only be visible through the window after the dollhouse is finished.
