I have done every test required to fix this issue and you can probably test it on your own game. I didn't know where to post this but it needs to be spread asap. Just build a basement and a room with a foundation above it. Then lead stairs down to the basement. Put a facing across so you can put a basement with nothing down as if wanting to expose below. It then shows the ground instead and it can't be foxed AT All!
https://dropbox.com/s/x35hqwui306xvth/06-14-20_5-32-53%C2%A0AM.png?dl=0https://dropbox.com/s/x35hqwui306xvth/06-14-20_5-32-53%C2%A0AM.png?dl=0
Comments
What you can try is: go down to the basement level, click the room and drag the arrow in the middle down. That should lower the basement enough that you won't get the hightened terrain around the house.
It is a known issue, which is posted on the AHQ, linked by Simpatsyann above.
Gallery: Kathykins
AHQ - Game help and Bugs