Prepping Old Plywood For New Tile


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Old 12-26-13, 05:45 PM
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Prepping Old Plywood For New Tile

We just ripped up the old tile which was something like 3x3 terracotta tiles cemented to the floor below it. I've attached some images below. You can see that we ended up gouging the plywood under it pretty badly. One of the images has the new tile that we plan on putting in.

Do we have to do any prep other than sanding down the very high spots? This is also our only bathroom in the condo so I will be taking out the toilet but that will be last minute.





 
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Old 12-26-13, 06:30 PM
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Welcome to the forums! Sand or scrape all the glue off the plywood. Then, with a layer of thinset, lay down 1/4" sheets of a concrete backer underlayment. Another layer of thinset and your tile. You can't successfully lay tile directly on plywood.
 
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Old 12-26-13, 06:41 PM
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what about some kind of self leveling underlayment? adding 1/4 inch to the floor is going to create some issues.
 
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Old 12-26-13, 06:58 PM
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Not as many problems as not using a cbu. Your tile needs an uncoupling membrane, by using cbu or Ditra, which can be purchased at box stores.
 
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Old 12-26-13, 07:25 PM
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Isn't that going to throw off toilet height? Also, whoever did this the first time around made the floor on one side of the bathroom flush with the hardwood leading in, and in our bedroom side the hardwood is maybe 1/4 inch higher than the plywood in the bathroom. I can take pictures if that doesn't make sense.
 
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Old 12-26-13, 09:31 PM
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You can add a spacer or a double thick wax ring to make up the difference.
There's almost always a height difference when tiling up to a different type flooring.
You use a threshold in the middle of the door opening.
Your going to have to come up with a plan B on using that bathroom.
No are you going to lay the tile board, tile, and grout, seal in one day. More like 3 days.
 
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Old 12-27-13, 03:24 AM
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Pictures would help, but, as Joe says, there is always threshold differences unless engineered plans are put into place taking into consideration flooring thickness from the beginning. Transition strips are available to help minimize the abrupt change in elevation, but you can't avoid it.
 
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Old 12-27-13, 06:49 AM
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They recommend putting down a wire mesh lath for use of self leveling compounds over plywood. The result will be close to the 1/4" you will get using cement backer board.

Why are you changing out the old (curious)? How many layers of plywood do you have and how thick is the combined thickness? Screw the plywood to the joists which I hope are 16" OC.

Pull the baseboard molding and you can replace when complete. This way you can tuck the cement board and tile underneath for a cleaner look. Undercut the door casings so you can tuck the tile there as well. Use a quick setting cement floor patching compound to fill in the divots made from the demolition.
 
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Old 12-27-13, 08:18 AM
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So I looked into Ditra and although more expensive it looks like the thinest option. So we'll put down some thinset, Ditra, let that set. Then mortar, tile. let that set, then last the grout.

Doesn't thinset set up relatively quickly? Allowing us to do that and laying the tile on the same day? Once we lay the tile we can go to my inlaws house for a day while that dries up so not having a bathroom isn't a problem as long as we time it well.

And the reason we are doing it is just for fun. Fiancee wanted a new look, the old stuff was probably 40 years old.
 
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Old 12-27-13, 11:19 AM
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DropSquad,

Please determine how many layers and the thickness of the old plywood. That top layer looks like it could be luaun from here. And it certainly isn't "the" subfloor.

You said the old tiles were there a long time. Well, that may be, but we recommend you do a better job now, and by using Ditra or concrete backer you will.

Let us know what you've got and we can help in your installation.

Jaz
 
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Old 12-27-13, 11:20 AM
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Carefully review the specs on Ditra as there may be a need for one type of thinset under it and a different one on top of it. Use the recommendations for use over a wood subfloor.

Thinset takes overnight to dry, and even then may still be somewhat soft in the morning depending on how loose you mixed it. The plywood will pull some of the moisture out, but I would let it set up overnight before setting the tile, it will not "air" dry in any way. I think someone else mentioned, that it will be a 3 day process - Day to put in ditra, day to lay the tile, day to grout. Then you seal the grout 3 days later, but should not prevent you from using the bathroom.
 
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Old 12-27-13, 12:51 PM
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Gotta disagree with our friend above from VA. Tile setting over Ditra can start as soon as you mix the proper thin set and decide the layout. The only official exception is if the big game is on.

Also note that the minimum size tiles over Ditra is 2", so go to plan "B" if you're using those i' hex. 1/4" concrete tile backer is for you. But first get back about that top layer of ply cuz it may need to be removed, and if it's 1/4", it's not doing you much good anyway.

Jaz
 
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Old 12-27-13, 02:34 PM
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Gotta disagree with our friend above from VA.
C'est La Vie...I always err on the side of caution and let each layer set up before moving on. Old habits are hard to break, but maintaining consistency is key. so I always know the outcome of my projects.... I even wait overnight on the hardibacker on the floor.
 
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Old 12-28-13, 10:37 AM
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So we went with wonderboard which was the thinnest backer we could find. Here is a pic of most of it down. There is still tile around the toilet because its the only one we have. At the last minute we will pull out the toilet rip out the remaining tile and lay down the backer board there too. After we put down the thinset and the backer board i'm going to give it an hour maybe and then we're going right to tiling. That we'll leave over night to dry up.

 
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Old 12-28-13, 01:25 PM
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Set your wonderboard in a mortar bed, 1/8" gap and tape all seams, and don't install it that tight to the walls. You have trim (1/2" base and 1/2" shoe) that will cover the edges. Installing too tight may cause tenting of the floor with expansion and contraction. Don't fill the gap between the backerboard and wall with mortar.

You may want to undercut the pocket door so that you can slide tile under to hide the reveal created.
 
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Old 12-28-13, 02:15 PM
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The base boards are cut so that they cover up that gap in the pocket doors. I'll trim down the edges on the wonderboard before setting them.
 
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Old 12-28-13, 06:10 PM
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This is where we finish for the night. The backer board is down on mortar, the seams are meshed over, and about 2/3 of it is screwed into the plywood but I ran out of screws and its 8PM so I legally my downstairs neighbor could call the cops if we keep up the noise.

Tomorrow, finish screwing it down, mortar and finally lay the tile.
 
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Old 12-29-13, 11:03 AM
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Ok, we haven't actually set down the mortar for the tile yet. Hopefully start that up soon.

When we're done, what do we do about this lip? The angle makes it look taller, but its probably about 1/2 inch.
 
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Old 12-29-13, 11:29 AM
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Yeah, with laminate, you won't have much of a rise on the wood side. Normal hardwood would be 1/2" or so higher and match better. Best course of action is to install a transition strip that lays on top of your cbu and meets your tile. Don't go over your tile as it creates even more of a trip factor. You may have to trim the points off your tile at the transition, but it will look so much better. Fasten the transition strip between the laminate and the cbu to the floor, not through the laminate as it must move.
 
 

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