Creating window openings with rounded edges

[Nate_M]

I am working on drawing an as-built plan for a 1800's farmhouse and ran into this unique scenario. The window openings have rounded plaster corners (see attached photo). I was actually able to hack together a way to mostly achieve the look of the existing window openings. Thought I might post some notes here in case anyone else runs into a similar need. Can't guarantee this is the best method, but I managed to make it look surprisingly close and it's going to work for what I need.

 

 

To make this work I used two separate walls placed against each other. Once walls are oriented correctly, I used a pass through window opening to create the larger window opening on the inside wall. I removed the casing, sill and frame to make it a very simple wall opening. Then I placed the actual window on the outside wall.

 

So far things were pretty straight forward. Where things got tricky was when I was trying to recreate the radius edge. What I ended up doing is creating a radius profile and adding that to my user library as a molding profile. Then I added window casing to the outside window using the radius profile. The casing needed to be depth of the inside wall so it meets up to the interior perfectly. The casing was added to all four sides of the window, but if you reference the photo you'll notice that's not exactly what I wanted. So, what I figured out to eliminate the top casing is to use a lintel. Once I added that it made to top of the window opening flat. I didn't really want to draw attention to the lintel so I made it only 1/16" thick. 

 

Finally, I adjusted the widths of the window frame on the outside wall to try and match the reference photo. I also adjusted the heights of both the outside window and inside wall opening to be the same height off the floor so it looks like there is a continuous surface. The last thing I did was to match the casing and frame color to the interior wall to make it look like a seamless transition.

 

Overall what I was able to make in Chief comes pretty close. I messed around with trying to create the rounded edge across the top of the window opening, but haven't had any success. 

 

Has anyone else ever ran into this scenario? How would you create this window style?