"sPoNiX" wrote
| I'm going to put some carpet tiles down.
| Is there any reason that these can't be laid across the
| existing carpet? Is there any advantage or disadvantage
| to doing this?

Don't. Carpet tiles are designed for laying on a rigid floor. If you lay
them on carpet they will bounce up and down and come apart at the edges.

| I'm thinking maybe insulation will be better and less likely
| to show 'ridges' where the floorboards meet if I tile over
| the carpet?

Hardboarding the floor first will help (a bit) with insulation and (a lot)
with floorboard ridges.

Owain