Do this in game using the half hipped roof.
How do you build a roof in sims 4.
3 some ideas to get you started tower.
Keep dragging until you are happy with the length.
Just add you would with the existing roof styles to extend the eave simply click and drag the small downwards facing arrow on the side of the roof.
Although it is entirely possible to get this to look good it looks nowhere near as attractive as using one of the new roof pieces.
Repeat on all four edges.
Quik tutorial how to make a flatroof in the sims 4 as for now you cant use the cheat constrainfloorelevation false like in the sims 3.
Build a smaller room on the roof about one or two squares from the edge of the building.
Adjust it to be flush against the wall of the room and pull it up to the same height.
One of the biggest problems with building a tower in the sims 4 was that you were often forced to use a 4 sided roof piece.
Add a half hipped roof along one edge.