This has come up in the contest play-along I'm building for the Fix or Flip contest. The house has a split staircase, using the split-level interior foundation. I used Steadfast Stairs for the four steps up to the interior foundation, and Holy Smoke Stairs for the 11-12 steps from the interior foundation to the upper floor level. I want my Sims to be able to use the space underneath the Holy Smoke Stairs. I'm fairly sure I've seen a mod which makes this space usable, but I can't remember where I saw it. Can anyone tell me what mod this is, and where I might get it?

this perhaps? :-) also quote:

All of HugeLunatic's recolourable modular stairs and the matching Open Underneath stairs have an edit to allow the space underneath to be used. I love the recolourable ones, nice and simple, just an override that upgrades the existing stairs; the Open Underneath versions use the textures from the recolourable ones, so that's practically a freebie, but you do have to fiddle with your scripts files to install them - I'm sure you have the savvy to make them work.

Thanks @vegan_kaktus and @Pebblerocker !

It transpires that I don't need a mod at all for what I was trying to do. It is possible for Sims to walk underneath base game Holy Smoke stairs. I honestly didn't know that. Here is Archie Forsyth walking under them to set the table for the lunch that he and his friends are serving to their first day Welcome Wagon visitors:

I'm sure though I'll find a use for HugeLunatic's recolourable stairs and Lord Darcy's mod some time. To do more with stairs, it seems that the mod I have to download, and learn how to use, is the Scriptorium (which I think is by Numenor). But, for the moment at least, I'm fine without it.

Thanks again!!