Here's a cool cheat i found for foundation walls. You have to modify the walls.txt Instead of holding down control to delete the foundation wall-this cheat will allow u to delete just one section of the wall instead of the whole thing.
If you go under sims2 folder ->TsData->Res->Catalog->Scripts->then click on the the walls.txt
Scroll down until u see the foundation walls towards the bottom of foundation walls it says DeleteTool levelroom

change levelroom to partition and save the file

when u create a foundation = if u click on the icon to create walls u can delete just one wall of foundation. Hope this trick helps

thx

So this makes it possible to re-wall your basements the easy way?

It more of an easy way of deleting part of a foundation. When u click on on the wall tool it will allow u to delete any one wall section of foundation-(example when u make a one square foundation normally if u delete the foundation the whole thing is gone-this will let u delete any side of the foundation and leave the remaining 3 sides in tact) Another advantage u don't have to be under the foundation tool to delete the foundation.

Did not work for me. I couldnet delet anything anymore. I have only be able to ad foundation but not to delete. Sorry!!!!

You have to be under the wall tool to delete the foundation-if u try to delete the foundation under the foundation tool it just deletes the floor tiles above and leaves the outer wall- hope that works for u twixraider-I forgot to mention u still have to use the control key to delete the foundation under the wall tool