and, yes, they contain asbestos but the mastic doesn't. The trouble with retiling is that the concrete is mildly curved downward in the area of a floor drain. This area probably has a two foot radius around the center drain and the drain is maybe a half inch below the floor surface. Since tiles don't stretch [?], this curved surface cannot be perfectly covered, so one suggestion was to paint the concrete. The tiles can be cut into a trapezoid shape which will approximate this funnel surface but I've never done this. Sounds like I should first experiment with all the loose tiles I have. . . It could also be that water poured onto the floor will pool and so this curved drain is only working within its radius and so I might as well bring the drain opening up to the floor level and then just retile. The upsides and downsides of either approach are welcome, including other options. You guys come up with stuff I never would have thought of.