Foundations - Please Help!

Possessionless

I'm having trouble building my home.
I was wondering how do you build those foundations or whatever on top, like the picture below

Please help! I want to know!!!
If you got tips or if you seen any tutorials on them.. please tell.
would be appreciated, thanks

Lawertend

http://thesims2.ea.com/exchange/story_detail.php?asset_id=37112
TS2 and TS3 use the same principles.

Now, when he says the cheat:
"boolProp constrainfloorelevation false"

Use this cheat:
"constrainfloorelevation false"