tile in a mobile home

[dog]

A job recently came up dealing with installation of 13" porcelain tile in a mobile home. The experts all seem to be puzzled. Thought I'd run it by this board. The specifics: 2 by 6 on 16" o.c. , 3/4" medium density fiberboard as only underlayment, at least 5 times more deflection than L/360 allows. Modifying the floor joists or rafters is out of the question. Adding subfloor material is impossible due to the height limitation, tile and backerboard is allready pushing it. Any ideas how to make this installation semi reliable with the limitations above. Thanks. By the way, great informative board.
Scott N.

[John Bridge]

Hi Scott, Welcome. Sounds like you might be in the business?

I've got to say it. I know it doesn't sound politically correct.

Ain't no way I'm puttin' floor tile in a mobile home.

[dog]

Hey John,
I know it sounds bad. But it has to be done, its one of those "trading labor for materials on another job". I was planning on using mastic to attach the backer, thinset might swell the MDF. Isolation membrane over that, and prey. Any ideas to make it more reliable? Thanks
Scott N.

[John Bridge]

Scott,

Since you put it on that basis . . . .

MDF doesn't swell that much, not like particle board and OSB. I would use the thin set, because mastic doesn't really provide any support, and that's what the thin set is there for. It'll dry up overnight, and any minuscule swelling will have occurred. I don't think the MDF will move after that.

There will be others along who know more about what I'm talking about than I do.

Don't give any guaranty, buddy.