Hello all,

I don't have a ton of flooring experience but I have tiled my shower walls using Hardibacker with a lot of success. I plan on tiling my parents bathroom floors later this year and just needed some clarification before I get started.

I plan on using Hardibacker again, probably 1/4" unless their plywood sub-floor feels in the least bit spongy, than I'll step up to 1/2" or even fix/replace the sub-floor if necessary. Their current floor as I mentioned is plywood with vinyl flooring. Can I simply screw down the Hardibacker over the vinyl, tape and mud my seams and begin laying tile? I'm sure I can remove the vinyl flooring but I just wondered if it was a step I could skip? Seems like it could be a decent makeshift moisture barrier?

What about using thin set under the Hardibacker, according to Hardy's website? It's the proper installation method according to them but what is the point, is the Hardiboard not held down enough with screws to the plywood and flooring joists?

Thank you all for the help.

 

Welcome to the forums.

What's under the vinyl - how thick is the plywood and is there anything else there? What size are the floor joists, what is their spacing and unsupported span? Are you planning to install ceramic tiles or natural stone?

The thinset under the backer board is to eliminate voids.

 

Under the vinyl is plywood, I'm not sure how thick but I would assume 3/4 is the industry standard is it not? The house is only a few years old so it's all in great shape. I would also assume 16" centers, but I'll look into both to be sure. Are you asking because you think the 1/4" is no good to use?

The thinset under the backer board is just to give a nice flat surface to start on, is it okay to apply that to the vinyl or would it be best to remove it? If I remove it is it okay to apply the thinset over the plywood, seems like I would be creating a moisture problem if there wasn't something between the plywood and thinset?

 

I think Mitch is suggesting that you do a bit of investigating to determine if the underlying structure is adequate to support the tile installation you are planning. My guess, based on the fact that it's a new house, is that the joists are adequate. However, you should measure the joist material span and width. From there you can determine if the floor needs to be stiffened.

Take a close look at how well the vinyl is attached. If it's still solid I wouldn't be concerned. A couple of months ago I tiled a bathroom for a friend. I tore up the vinyl. Half way through I wished I had left it in place. It was 100% attached and a PITA to remove.

I too have asked the question regarding bedding cement board in thinset. I'm a DIYer and not a tile pro, but I just can't see why it's needed. I skip that step, so far without a problem. I understand Mitch's response, but I always make sure that the subfloor is flat before I put down the underlayment - with a million overpriced Hardi screws.

 

To add to the comments, 1/2" cbu won't be necessary. The cbu offers no structural strength, only a flat medium to apply your tile. So if your subfloor is solid, then you can apply the 1/4" cbu and tile.

 

1/2" is no better than 1/4" CBU adds no structural strength. It needs thinset under it or the tile job will fail.

 

You have addressed several issues so let's tackle them, one at a time.
1)If the subfloor is at all "spongey", fix it before going any further. The subfloor must be sound and "flex" or "deflection" free before ever starting a tile intall. As was stated earlier, backer board provides no structural strength to the job. 1/4 inch is for floors and 1/2 is for walls. The only time this is not adhered to is if there is some transitional thing you're trying to solve where 1/2 inch will provide a better transition. Normally, especially where tile and carpet will be married, 1/4 is the best for a smooth transition. The only pourpose of backerboard is to compensate for different expansion and contraction rates. When installing tile to concrete, backerboard is not required because tile and concrete expand and contract at the same rate. They will remain adherred to each other. Tile and wood have dramatically different expansion and contraction rates and there must be some sort of medium between them to compensate for this difference. Back in the day, this was accomplished by different methods, some of which are still employed, such as a mud set. But, in today's world, backerboard is the most common means of making up for the difference. It is not the only means, however, just the most common.
2)Vinyl flooring is called "resiliant" flooring. It will allow the tile install to flex and fail over time. Tile is NOT flex friendly. If I were putting tile in my own home and were willing to take the chance, I'd go ahead and do it. But putting it in someones elses place where my name is on the line and there is the potential of having to go back and do it over, I'd remove the vinyl.
3)Thinset under backer board is not used to glue the board to the floor. It is used to bed the board, thereby eliminateing any voids between the board and subfloor. Your subfloor is not going to be a perfect match to the backerboard so the thinset makes it one. Again, tile installs are NOT flex friendly and the surface you adhere it to must be very stable.

 

This could be pretty simple fix peal the vinyl up scrap the access up tile on the ply with morter thinset.
Backer board isn't structural for flooring.