Ceramic tile, backerboard needed?

[ndemge]

From my understanding, normally on a upstairs floor, you Mortar and screw down a backerboard, then morrtar and tile, to stiffen the floor so the grout doesn't crack.

My house is 5/8 Subfloor

In the kitchen and bathroom, each has another layer of subfloor on top of that.

I recently put down laminate in the living room next to kitchen and noticed this. When I walk in the living room, you can feel a huge difference vrs the stiff kitchen floor.

Do I need the backerboard? If so, I'll need to remove the 2nd layer of sub because it will bring it at almost an INCH between the tile and wood floor, too much of a trip hazard, but not enough for a step

I don't know any floor guys to get the true answer, I would hate to put down my tile only to have it all cracked in a few years.

[Rich]

5/8"? Really?
I would probably run another layer of plywood the opposite direction to stiffen the floor. Then use a 1/4" cement board backer (Not durock).
The backer board does not need to be mortared under it - just screwed.

[roger g]

I'm still curious also as to what happens to or with the height difference that you now have. One site on tiling advised laying 2 layers of 1 1/4" plywood. Jees! at that height you would almost need hand rails at that location.
Maybe in new construction you can lowere joists in certain locations but in reno's I see a real problem.


roger

[Rich]

No need to lower joists in new construction - first off you don't use 5/8" plywood. I use 1-1/8" - no worries about deflection. Typical hardwood is 3/4", carpet is about 1/2", and tile is about 3/4"-1" with backer. IMO those offsets are close enough to be taken care of with transition strips.

[Dragon]

Yes, you need the backerboard. Thinset doesn't stick to subflooring well. Your tiles will come loose in no time without it.

[ndemge]

Thanks for the replies.

guess I'll see how bad my step will be, and if it's too bad, remove the 2nd layer of sub and have at it

[MikeD]

No need to lower joists in new construction - first off you don't use 5/8" plywood. I use 1-1/8" - no worries about deflection. Typical hardwood is 3/4", carpet is about 1/2", and tile is about 3/4"-1" with backer. IMO those offsets are close enough to be taken care of with transition strips.

Do you really use 1 1/8 plywood for all subfloors? Nice and stiff but heavy (who cares like you said b4 as the framer's doing the lifting!). Seems pretty expensive, is it worth extra $$ over typical 3/4 plywood?

[Rich]

Yep. And umm.. .I'm the framer :)
Just my personal preference to be honest - no reason to chintz on a floor that I'll be walking on everyday IMO.

[Tom R]

Yes, you need the backerboard. Thinset doesn't stick to subflooring well. Your tiles will come loose in no time without it.

I've 'flex-bond'(ed) ceramic tile floors to plywood (1 1/4" build-up) plenty of times with complete success.

Including my own bathroom (11 plus years ago).

I did a 'regular' customer's kitchen about 15 years ago, it hasn't had any problems, nor have any of the other one's I did. It's just real important to use the right 'thin-set'.

Once I also applied hardware cloth to the plywood, but that's because it was a 'cold' floor (raised ranch on the coast that's 'shut down' for the winters). Just wanted to make sure.

[Dragon]

What thickness and joist spacing?

[Tom R]

Joists 16" O.C., with 3/4" plywood, then 1/2" plywood, - - glue and ring nail the first layer, then 'spot-glue' and screw the second layer. Then 'Flex-Bond' thinset made for plywood applications. I do 'em all like that, - - never had a problem.

[MikeD]

Yep. And umm.. .I'm the framer :)
Just my personal preference to be honest - no reason to chintz on a floor that I'll be walking on everyday IMO.

Rich, you use 1 1/8 on 1st and 2nd floors or just on 1st floor?

[Rich]

Wherever there's a floor.