Flooring Tile - Backerboard help

I am having travertine installed and am wondering how I should have the backerboad installed for 800 square feet of tile on the floors.

One installer said he uses mortar (or something like it) to install while another just staples or nails it down. It is new construction with one layer of plywood subfloor. The subfloor is pretty level with the occasional uneven edges, ect. Please advise. Thanks

Installing backerboard should be done with a layer of un-modified thinset (no latex additives) spread out underneath the backerboard and screwed down. The screws will keep it down, and the thinset acts to fill any voids between the plywood and the backer.

But back up a second. Natural stone needs a bit more support than ceramic tiles. How thick is the one layer of plywood?
Might also want to check the joist sizing, spacing and longest unsupported span.

Before you get to far ahead there are some things you need to be aware of and do for natural stone. Your floor must be twice as strong for natural stone as it must be for ceramic tile. Your floor must meed L720 for natural stone. Your installer should know what that means. If not get someone else that does. Make sure your floor is strong enough for natural stone before you go any further.

You'll need at least 2 layers of plywood for a minimum total of 1 1/4". The cement board must be set in a bed of unmodified thinset and screwed to the plywood. Your installer should know this also. If not get someone else that does.

You mentioned new construction and most new construction these days they are using I-joists or truss systems. If this is the case they may be spaced more than 16" on center. If so you may not be able to use cement board at all. Check out the website for the cement board you intend to use. They all have installation guides that tell you what you can and cannot do. I think all say if more than 16" oc no go but check anyway.

Its good that you came to the board for advice. The info here will help you to find the right tile setter and a good sound installation.:)

Good Luck:)

We did go through the strength issues. My builder ended up using 2x12 16"oc and doubled them up in areas of a lot of stone. He claims the engineer ok'ed this system for the load. He says I do not need two layers of plywood because he doubled up the 2x12's and where he did not is right over the support beams. Does this sound like enough?

The 2x12's are probably ok depending upon the span. All stone installations require 2 layers of plywood 1 1/4" thick.:)

span is mostly 20 feet, but that area is has the 2x12's doubled up. The other span is 12 ft, my builder is not going to do 2 layers of plywood subfloor. I guess I will keep my fingers crossed. Thanks for all the help

Get a warranty in writing that specifies it was his decision to go against accepted guidelines. In a year from now you will be searching for it. Was his guy the one that did not want to put the thinset under the cement board?

The 2 layers of ply is not optional - it is required. It makes no sense to do it wrong knowing its wrong and will fail. Crossing your fingers is not going to help.

Your builder needs to accept the outcome and stand-ready to reach into his pockets when your floor tile cracks. You need HIS gaurantee in writing.

The added plywood is to defend against "deflection between the joists". The sistered 2 X 12's are nice but probably not totally necessary, not as necessary as the added plywood is.:) Single 2 X 12's would have done the trick and saved more than enough money to buy the extra plywood that is required.

This is all in books....can your builder read?:)

The plywood layer looks like it may not be the worst of my problems. The tile installer came over to lay down the backerboard and said there are areas of the subfloor that are not level. He said it may be the 2x12 joists have bowed in a few areas. He does not want to lay the travertine until this issue is resolved because the tile will have high and low spots leading to problems down the line. Any idea on how to remedy this!!!

cj,

You can thank the Tile Gods that you apparently have a wise tile installer in your grasp.

All dimensional lumber has curves, it just happens. Anytime a builder is working with any dimensional lumber he should know that he must "crown his boards". This means that he takes the time to look at each board along its length and determines which way the 'crown' bends. THEN he is to turn all the crowns in the same direction. In a wall it matters not which direction as long as all boards are crowned in the same direction.

In a floor however all crowns are to be placed upward. Not one up and one down in haphazard fashion. It sounds to me like this is what has happened.

I'm sure no one is going to remove the joists and start over so the only other options are to:

1. Either install the backerboard and fill the low spots or,

2. Use SLC (Self Levelling Compound) on the entire area. aybe your ""builder"" should undertake that cost on his own.:)

Depending on how serious the waves are #1 may not be do-able.
:thinker:

My tile installer grinded down the subfloor to level it as much as possible. There were just two areas where the subfloor was arched directly over the joists, he grinded it down to almost level. My question is: Am I better off going with 1/8 inch groutlines instead of 1/16th. I am not worried about the tile not being even (It is florida tile and my tiler even called them to make sure the travertine was cut perfect). Will going to 1/8th inch make it easier to hide small imperfections in the floor, and will it make it less likely to crack? Thanks again for all the help!(I feel like I should send you a check for the money you have saved me in future problems)

This floor has been in discussion for a very long time now. You obviously care that it's done right. The second plywood layer wasn't an option before. Now that the plywood has been ground down, those areas have lost significant strength. Probably wouldn't even be strong enough for a ceramic install now.

cj

Dont forget the second layer of plywood.:D

Or mud the floor, either way, listen to the others and get another layer of plywood down before a CBU or membrane, or kick those hacks out of the house, it's your home, written guarantees are fine, but who wants to go to court for years arguing who's responsible when it fails and getting it redone, meanwhile you are the one who has to live with it, do it right the first time or don't do it at all, sorry to be so blunt, but I here this all the time.:wall:

I keep reading reference to CBU or cbu in postings. Is CBU or cbu same as cement board?

CUB is concrete underlayment board.

CBU stands for Cementitious Backer Unit.:rolleyes:

I saw two products that may be used for backer board for tiles. Hardibacker and Wonderboard. Which is more suitable for use around shower and bathtub walls. I plan to put ceramic tiles on these walls.

Both of these are good products. Either will do the job fine.:)