Quicksand problem

In a level I'm building, I have buildings sinking in quicksand, but there's a little problem when you're on them and they sink to the ground:

Here's an overview:


When you come close, The building sinks:

Still looks good:


Here's the problem (I'm below the quicksand now):


Overview again:

Anyone know how to solve this?

Make a fake FOF so you won't sink too low for that to happen, maybe?

I dont know if this will work, but its just a wild guess..... Uh maybe in the whole area that the sand is in, you can make an FOF thats translucent, has no textures and isnt solid, but you can pass through it, so the FOF will be invisible and intangible... But, the FOF should act as a blocking mechanism for the sand.

Do you at least kind of understand what im saying? Because i really don't think i was too clear in that statement -_-'

I'm attempting to create a S3&k sand effect for my level and has this problem as well but sonict's solution worked fine.

If it were me, I'd do something overly complicated that would work just as well.

Just go with Sonict's FOF solution. Also, make sure there's quicksand tagged to the building sector too.