Platforms and Stairs not functioning properly in Basements

[InfinityD4]

Product: The Sims 4
Platform:PC
Which language are you playing the game in? English
How often does the bug occur? Every time (100%)
What is your current game version number? 1.90.375.1020
What expansions, game packs, and stuff packs do you have installed? Base Game, Free Content
Steps: How can we find the bug ourselves? Simply attempt placing Stairs to or between platforms in a Basement.
What happens when the bug occurs? Cannot place, Incompatible with Terrain Restraint Block. However placing them one tile away works fine for some reason, and properly conforms to the level of the platform.
What do you expect to see? Placement to be the same as in non-basement rooms
Have you installed any customization with the game, e.g. Custom Content or Mods? Not now. I've removed them.
Did this issue appear after a specific patch or change you made to your system? No

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Can't use stairs with platforms in Basements for no good reason.

[CGrant56]

@InfinityD4 

Can you add a pic or two to your post of what you are trying to do?

I tested placing stairs that land on a platform in a basement and had no problem with it.  I tried it will all 3 wall heights and with and without a foundation.  I did not get a terrain restraint block error.

And if you are willing to upload the build to the Gallery and reply here with the lot name and the UserID, I am willing to test the lot to see if I can find what is going wrong for you.

Hope this helps.

[InfinityD4]

I should have doen more testing, my bad. seems that the requirements are extremely specific. It only affects the first basement level, and it's caused when the room the base of the stairs are in has no ceiling, so that it's open to ground level.

[CGrant56]

@InfinityD4   Thanks for the pics.

What I see in your pics is that it appears you have a platform on top of another platform.  Both appear to be 2 clicks tall.  The ceiling has been removed over the center section and the stairs will not place between the platform in the middle and the one at the back.   I think the error is misleading you too. 

And I think I know what is going on and why you are getting the error. Not completely sure since I can't see what the wall height is (short, medium or tall) but I think you are using short walls.  What I think is happening is there is not enough head room where you are trying to put the stairs. 

So, try raising the walls to be taller and see if it works.  Another thing you can try is dragging the whole basement down with the big arrow in the middle when you select the room. If the stairs will place then, drag the basement back up until you either get another error or the stairs disappear then back down one click and place the stair again.  You can also try deleting the ceiling over the back platform, place the stairs and replace the ceiling again.

If none of that works, then come back and we can go from there.  I will try to replicate what you are doing and see if there are other options.

Hope this helps.

Edit.  Well, I tried to build your configuration and got the same result you did.  It works if you don't delete the ceiling.  Otherwise, it won't work in a basement regardless of wall height.  Dragging the basement down doesn't work either.  It does work above ground though.  I did find a way to make it sort of work to achieve almost the same look, but it will really limit your choice of floor tile.  See the pic below.  From all appearances, this looks to be a limitation in the build system

Hope this helps.