Can't delete floor?

[KnowitallSim]

I figured I'd come here since the TS3 site somehow deleted my account a long time ago and it cannot be recreated, but that's a different glitchy EA mess. Anyway...
(I'm running with only WA, most recent patch. No CC or Awesomemod although I've been meaning to download it)

I've been having this problem with the Goth Mansion. In this one room, there is a large chunk of tiles that are occupied by something, supposedly, and they cannot be deleted. The problem has persisted for a very, very long time in game, and I'm not quite sure what initiated it. It's not gamebreaking, but it's annoying to have a room you can't use. I've tried everything (moveObjects, sledgehammer, etc) and nothing works.
Here are a couple of pictures (they're a little dark for some reason):



Sims can't walk onto the glitched tiles. Objects cannot be placed. They cannot be deleted.



I changed the floor and wallpaper, deleted everything. The dark squares in the area highlighted by the sledgehammer are the parts that are impossible to delete.
Can anyone help? 

[Tingeling]

The Goth Mansion is known for having bugs like the question mark tiles. I am not sure why you are unable to delete the floor, so my suggestion would be to move the family out and replace the mansion altogether. I downloaded a remake of the house here which is in my opinion an improvement and a hasslefree abode for my sims.

Come to think of it, there might be an issue with the level of the floors. Check the leveling on the floor above and below to see if there are any warped tiles there.

[morriganrant]

LikeTingeling said, try checking the floors level. Even if you don't see the floors warped yourself, try using constrainfloorelevation false on the floor below and the floor itself.

[KnowitallSim]

How exactly do I check if the floors are level? I enabled the cheat but it says 'only exposed terrain can be edited'.

[Tingeling]

Try dragging the flattening floor tool over the area. Sometimes you can't see the wonkiness in the floor tiles. I have no idea why it is complaining about the terrain. If the cheat has been used successfully, nothing like that should happen. Unless you have used the terrain paint tool and tried to paint the floors with it.