From what i know:
Trying to build a basement in a house made prior to the update that made stairs recolorable (and that hasn't been properly updated) causes crash.
Trying to build a basement on a house where the moveobjects cheat has been used to place things off the grid, with this being done prior to WA patch, can cause crash.
Other than that, i do not know what's causing it for you. Try it in different empty lots, if it happens elsewhere too, it means your previous lot was somehow bugged/corrupted.
Try moving your custom content elsewhere and cleaning up the caches to check if that's what is causing it (even if you don't use custom content, try the cache cleaning thing), if doing that fixes it, move back your custom content one by one until you find the culprit.. or not, in which case the fault was of corrupted cache files.
If that fails, try creating a new neighborhood and see if it still happens, if it doesn't, then your savegame got corrupted somehow.
If that ALSO fails, try doing a game reinstall/repatch.