[BY DESIGN] Terrain height changes when basement is drawn to edge of structure

this happened to me as well. I was able to fix it by lowering the basement down by the same number of clicks as the foundation was high. In other words, if  your foundation is one click high lower your basement one click and the terrain will be flat again.

I have the basement-foundation issue too and it is connected with not being able to fully zoom into the basement.

Thanks to all the good information, I've been able to reproduce the issue, and it's not lot dependent.  The trick of lowering the basement height by the foundation height does work to correct it, but I tend to think it may be a bug for the terrain to shift in that manner in the first place rather than the basement height being automatically adjusted to conform to the foundation.  Will add to our list.

Placing a basement is supposed to flatten the lot directly above it. If it's uneven before placing the basement then the terrain will change, and that's expected design. You should also be able to use Flatten Lot again to correct any weirdness, or lowering the basement should fix it. But if you believe that the lot was already completely flat before you placed the basement could you possibly share a save file with me? Knowing your exact order of operations could be important as well, sometimes B/B bugs only occur when you follow a specific set of steps. Thanks!

@SimGuruNick This happened in more than one save for me with the Blue Velvet lot when I tried to add a basement (I shared screenshots earlier). If I directly added a basement without lowering the building so there was no foundation, the terrain raised to cover the foundation wherever the basement wall met (or exceeded) the main floor wall. I undid the basement add and tried the flatten lot tool before trying again and it made no difference. The only thing that’s worked for me when I have this problem is to remove the foundation (ie lower the build so there is no foundation and it’s even with the ground), then add the basement, and the add the foundation back on after the basement has been added. I ended up staying within the main floor outer walls (this includes porches) with the basement I added before I realized that (the renovated Blue Velvet with the basement is on the gallery, though it probably won’t help you since I kept within those ‘lines’). I can try and send some saves that I experienced this in when I get into my game later).  I can’t say I notice it on every lot, but I did have an issue with the StrangerVille lot (the little one with the trailer park) when I tried to add a large basement hidden ‘lair’. 

Best regards,

Jennifer

@SimGuruNick  I was able to recreate this on three different lots in the linked save (this is not where I originally had the problem).  I did have MCC and one other small mod in my game, but before I recreated this issue I removed them, deleted my localthumbcache and repaired my game (I didn't have either when I originally had this issue). The lots in question where you can see the terrain issue are The Blue Velvet, Arid Ridge and Slip 42. 

With Arid Ridge, the block with the problem is one where I built the 'block', raised the foundation and then added the basement to part of that block. The block with no issues I built the 'block', added the basement and then raised the foundation. Both Blue Velvet and Slip 42 have buildings so you can just see the impact of the partial basements I added.  I did not try the work around on either the Blue Velvet or Slip 42 lots in this particular save. Also, I wasn't able to extend the basement of the Blue Velvet to the edge of the building on the street, the build 'line' turned red and the game wouldn't let me.  I had this problem in another save when I was first testing it out.

Also, I renovated the Goth's lot in this save (I did that on the weekend and at the time the two mods were in my game) and had added a basement which was within the main floor's floor plan (this includes porches).  I just went back in to see if it had an issue with the terrain if I extended the basement and I did (I dragged the small basement to be at edge of the porch).  This isn't showing in this save as I thought to try that after I had zipped and uploaded the save to my One Drive, but you may be able to recreate.  Let me know if you would like me to resend the save with that done. 

https://drive.google.com/open?id=1UlLmYQ6Icc_Jx9XWaTixNXWjOUyTYXJR

Best regards,

Jennifer

@MapleSimmer Thank you so much for all the detailed info and the save file, it's incredibly appreciated 🙂

@SimGuruNick  You’re very welcome. Hopefully it will help. 😊

Best regards,

Jennifer 

Just in case anyone is still having this issue, I realized tonight while playing that to fix the terrain, you have to lower the basement below the level of the foundation. So, click on the basement, and use the arrows as if you were placing a foundation to instead lower the room. It will leave a slight gap between the basement ceiling and the floor above it, but the stairs will adjust themselves and you can't really notice the gap unless you tilt the camera just so. 🙂