Date: 4/27/2008 3:49 pm EDT
Wow, sounds like an interesting archeology project....
If I read the situation correctly, there is a layer of sticky tar/glue exposed. You won't want to install Avaire tile directly on the tar/glue. If the floor is flat enough, you could install a very thin layer (1/8") underlayment that would isolate the tar/glue from the Avaire tile. That won't add much height, but will give you a smooth, flat, clean surface for the Avaire tile.
Three reasons you don't want to place Avaire tile directly on the glue. First, without knowing the composition of the glue, there could be an interaction between the polymer tray and the glue. Second, it may be difficult to properly install the Avaire tile over a sticky substance since the installation method requires the tiles to interlock while flat. Last, since the floor is designed to float, you might hear the tile "sticking" and "unsticking" to the glue below when you walk on it.
Let us know what you end up doing.
Thanks for considering Avaire.