This is a exampel of gable window it is done whit defult projekt settings.
1. Copy grund floor ext. walls to second floor.
2. Work on second floor.
3 mark the walls on the long side, in the propertis of walls go to Top and Bottom tab mark Level in Wall Top make the Wall Heigt for exampel 2" then hit ok.
4. In propertis for the gable wall you can change the offset of the Wall Top to make the connection between wall and roof better but I have use standar settings I the attachment, ensure that Auto extend is mark.
5 make a gable roof on top of 2.nd fl.
6 Mark both the Hip side of the roof go to roof properties and Support and Details tab, in support height make it the same height as the long side wall. You can exprement whit the other setting for the Hip so you gott the roof you will have. Hit OK. And now you have a attic
7 Chose a window and and fitt the level to the gable height, if you will have 2 windows you maybe have to changes in the roof and wall propertis to make mor space for the windows.
Atchment gabel-window.zip is the bld file of this exampel
Robert