Nothing to be sorry for @AbellaKellaher . This is indeed for Sims 3... was just double-checking :smile:
What kind of curve are you trying to make?
Are you just using the roof tool? If so, perhaps the tutorial link below can help (see conical, dome, pagoda roofing tools). And yes... you can apply this easily to a house with a foundation using the standard tools. Just select auto-roof or add individual roofing pieces depending on what you want it to look like. The pagoda and curvature tool is great for curves for cottages, etc.
https://carls-sims-3-guide.com/buildedit/houses/roofs/https://i.imgur.com/2fAVaqH.jpg
If you are looking for a more sophisticated curve using the ConstrainFloorElevation (CFE) false cheat that's more complicated. If you're just starting out with CFE, perhaps the tutorial below can help. There are other CFE tutorials on YouTube as well.
https://carls-sims-3-guide.com/buildedit/houses/walls/wallcurving.php.
If you are already comfortable using CFE, and just need to get around the foundation height popping back to a standard height when manipulating, then you can try what I did below. I think this method including the foundation in your guide walls is easier to manage...
First pre-determine the number of clicks in advance to make the curve you want. With that info you can lower the terrain where you plan to add the guide walls by the same number of clicks. Add a piece of foundation and guide walls. Then use CFE to curve your roof. In the example below, I started with the highest point of the curve (less lowering of the terrain); then the next set of guides I lowered the terrain even more since wanted the ends to curve downwards. Keep in mind placement of your guides in case you mess up and need to redo anything, it's good to have backup guides somewhere on the lot which you can use to fix things. A quick and dirty show and tell below assumes you already know to use CFE. To get a smoother curve, repeat at least 3 times and use less clicks between lowering. Remember to turn the cheat off (true) when done.
https://i.imgur.com/osrqCrJ.jpg
Hope the info above helps. Others may have other CFE methods as well. I find making backups of your WIP lot and just experimenting a great teacher. Good luck!
