5/8 is minimum under 2cm stone slabs, so it sounds about right for the stuff you're having done.
If you know the manufacturer, you can look up the installation instructions for that product to verify - check their website. If you're thinking about going thicker, I'd verify with the fabricator that it'll be hidden by the new counter-top edge and still allow clearance at any doors or drawers.
edit; when we say 5/8 now, we usually mean 5/8 nominal, not exactly 5/8. So 19/32 cdx is typical for those sub-tops.
"the road to hell is paved with osb, mastic, pre-mixed latex 'grout' or 'thinset', "
Last edited by dhagin; 03-08-2010 at 05:45 PM.