Hmmm, I posted a response to the above "More Inforamtion" a few days ago and it seems to have disappeared, I wonder why?
Billy, the trusses on 20" centers make this floor basicly unsuitable for a reliable tile installation according to the TCA Handbook and ANSI 108-1992. Even adding posts and a beam, while perhaps reducing any flex due the span, will not make up for the fact that the 16" oc requirement is exceeded by 25%. It is not impossible that some combination of setting materials will give accepetable service for some years, but finding them may be the trick, and the prospect of periodic replacement of tiles and or grout looms. I hate to be the bearer of bad news but facts are facts.