I thought I'd share briefly about finishing ceilings. This is the dining room of my latest house. I used a combination of things to do it. The ceiling itself is acid-free matte board. (I use acid free materials whenever I can in my work, since I want my grandchildren and maybe even great grandchildren to be able to enjoy my miniatures long after I'm gone.)
With wooden dollhouses, I think matte board is really the easiest way to finish off ceilings. A small piece of molding around the edge helps to hide any imperfections as well as to help hold the matte board in place.
Even though I thought my walls were perfectly straight and all corners were 90 degrees, I checked to make sure using a right angle square. If any corner was not precisely 90 degrees, I would have had to adjust the angle of my miter cuts for that corner. In cases where my ceiling has a cut-out or extends into a smaller nook area, I create a paper model of the ceiling before I ever cut out the matte board. (Saves making mistakes in cutting.) Be SURE you mark which side is up so that when you place the model onto your matte board to draw lines, you have the proper side selected!
I purchased the sconce above the chandelier as well as the ogee and dentil moldings around the edges of the ceiling. (I've tried making my own dentil molding. It's a pain.) However, I did make the octagonal molding that floats around the chandelier sconce. To do that, I cut out straight pieces of wood approximately 1/4" wide and then I used a compass to draw quarter inch wide arcs on the same kind of wood as the straight pieces were cut from. I then cut out the arcs with my table jigsaw.
Next, I used my Dremel tool and one of the Dremel router bits to create the indented and rounded effects of this piece. I routed both edges of each piece. I then used an emery board to smooth out the top of the rounded "bead" to remove any imperfections.
Next, I set my table saw miter gauge at 22.5 degrees. I cut the straight pieces in appropriate lengths so that I had two sets of equal length straight pieces. Then I cut out an arc that filled in the remaining portion of the inner curve of the routed pieces and created a right angle. Holding the curved piece against the arc, I was then able to cut the 22.5 degree angles into the curved sections. The last step of creating this molding was to carefully measure where I wanted the molding to go on the ceiling.
I should mention that I worked on the ceiling outside of the dollhouse. I cut the matte board slightly narrower (about 1/16th inch) than the length and width of the room, so it would go in easily. I then centered the sconce in the middle and glued it into place. With the ceiling flat on the workbench in front of me it was fairly easy to measure and piece together the molding pieces described above. Next I glued the matte board into place. I used a few pieces of thin wood that were about 1/16" taller than the floor to matte board ceiling. I bent these and set them in various spots around the room to help hold the matte board in place while the glue set and dried. (I used at least six boards to hold up the ceiling.) Once the ceiling was firmly in place, I glued in the ogee/dentil moldings.
By the way, I use a capenter's ruler to get precise inside dimensions for the molding. I find it a very helpful tool. Most any hardware that sells tools also sells these rulers. They are eight inches long when folded up. The segments can be twisted 180 degrees to extend out, making the full length of the ruler six feet long when fully extended. Inset into the last piece of the ruler is a sliding brass rule that can be extended. You can insert the folded up ruler into a room, push out the brass extension and get a precise reading of how wide your room is.
It's crucial to get precise measures of the room so that you can cut your molding exactly. If your measurements are too wide, the molding won't fit in the room. If it's too narrow, you'll have ugly gaps in the corner(s) or molding that doesn't go all the way to the wall.