I recently scored an unreal deal on some large format tile at a liquidation auction. I will use it for a  build this summer where it will be replacing the originally spec’d vinyl plank flooring. 

But when I say large format I really mean LARGE FORMAT. Its 24″ X 48″ porcelain tile! The now defunct business sold to clients building commercial or institutional buildings, not typically residential. 

I think I have a reasonable expectation of the increased difficulty of installing LFT, so I definitely don’t want to make things even harder by having a subpar floor assembly on which to install it on. 

At the moment the plans spec 14″ I-Joists, 16″ O.C. for an 18’6″ Span, with a 23/32 subfloor.  

I’m wondering what I should do to beef up this structure to minimize deflection. Off the top of my head I’d say doubling up or decreasing the spacing of the I-Joist at areas with increased dead- and live-loads such as the kitchen table and peninsula. Using screws with reduced spacing between the fasteners and glue for the subfloor, and adding a  layer of APA Group 1 or CANPLY 0121 exterior-grade plywood underlayment, offset from the subfloor. Again glued and screwed with reduced spacing but not fastened through to the I-Joists, to allow some isolation between the underlayment and the framing.

Finally, I would likely use a decoupling membrane and a thin set designed for LFT installations. 

I’ve never seen the Advantech Floor panel used in my area (Alberta, Canada) but I wonder about sourcing that for this project. 

LFT installation in a residential setting hasn’t caught on yet here so I am hoping someone else has experience with this and can provide some guidance. 

Thanks in advance to the great community!