Plywood Floor

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  #1  
Old 12-20-00, 07:43 PM
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I am currently preparing to install ceramic tile in a kitchen that is approx 12' x 20' with a 1/2" plywood sub-floor. The newly installed 3/4" exterior grade plywood underlayment takes the level of the floor about 3/8" below the height of the floor in the adjoining room. The thinset and ceramic tile will bring the kitchen floor height up to match the surrounding floors.

I have two questions:

1. Is plywood an acceptable surface for ceramic tile ?
I am not comfortable with the additional height that would come with another layer of thinset and 1/4" backer board (wonderboard). Please include any information regarding preparation using plywood.

2. The gaps between the edges of the plywood is 1/8". Is it necessary to fill these prior to installing the ceramic tile?

Thanks
 
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  #2  
Old 12-21-00, 03:03 PM
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Well . . . I think you are going to go directly over the plywood no matter what, eh?

I'll first say that plywood is not a recognized substrate for ceramic tile. And now I'll tell you how to do it.

Screw the plywood into the joists with deck screws every six inches in the field and 4 inches on the joints. Then use a very high polymer thinset -- TEC SuperFlex, for example. This stuff will cost you in excess of $20 per bag. Wait a couple days before grouting (stay off the floor). Clean everything up and start holding your breath. You might just get lucky.

John

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  #3  
Old 12-21-00, 07:27 PM
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John,

Super Flex is a latex modified mortar not a polymer modified. Polymer additives are low cost, man made and inferior to the more costly, natural, latex additives.

Re: Plywood

You have the proper plywood thickness (1 1/4") and you should have floor joists spaced a maximum of 16" on center. After you have installed plywood sheeting (sounds like you have) use a rough sander (about 80 grit) to rough up the surface. Prior to installing tile use hot water to damp mop (I stress damp, not wet) the plywood. This will also help to improve the mechanical bond of the thinset mortar to the substrate.

Wait 24 hours before grouting.

By the way, installing on plywood is an accepted industry practice when installed according to TCA method. Millions upon millions of square feet have been installed in this fashion for decades. In light of more improved methods most experts discourage installing tile using this method as plywood is more vulnerable in terms of failures due to moisture. However, installed in a dry area using approved methods it will shine (as John says) for many years to come.
 
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Old 12-21-00, 08:29 PM
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By the way jschweiss,

You can greatly enhance the life of your new tile floor and reduce some of the moisture concerns if you install a waterproofing membrane similiar to Trowel & Seal over the plywood. See link for more info.

http://www.custombuildingproducts.co...20&%20Seal.htm
 
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Old 12-21-00, 08:51 PM
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Ceramic Tile on Plywood

Thanks for your responses to my post! Here is an update, let me know if I am pointed in the right direction....

As you guessed, the plywood has been installed on top of the 1/2" plywood sub-floor with joists at 16" centers. I screwed the 3/4" plywood every 4" throughout the entire floor.

I have not yet filled in the 1/8" gaps betwen the sheets of plywood, but have been told to do so with a floor leveling compound. I am not sure this is necessary or makes sense. The gaps were created for expansion. Doesn't filling the gaps defeat the purpose the the expansion joints? Please help me with this one. I was thinking that the thinset would fill the gaps during installation of the tile.

I shopped around at the local hardware stores and found a thinset material that was recommend specifically for use on plywood. It is called "FlexBond" flexible bonding mortar by Custom Building Products.

In a previous reply, an appropriate material was refered to as "Super Flex". If this is a better material for plywood application, please tell me where it can be purchased.

I have no idea how this compares to other thinset materials. I would like to hear any comments about this material or from anyone with experience (good or bad) with this material.

Thank again for the help.
 
  #6  
Old 12-21-00, 09:26 PM
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I guess you have been shopping at Home Depot...

I would recommend that you go to a tile supply house (where the contractors go) and purchase a latex modified thinset(mix with water only). Or purchase a non-modified thinset mortar and mix it with an acrylic latex additive (the white stuff). A non-modified thinset mortar should say or recommend on the bag to mix with an additive like this.

Remember to skim coat the plywood with thinset mortar as you work. It also improves the mechanical bond.

No do not fill the gaps with leveler. Like you say these are expansion gaps and should not be bridged with setting material.
 
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Old 12-21-00, 09:37 PM
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By the way FlexBond is a latex modified thinset. I have noticed though that Portland cement based products tend to sit a longer time on the shelf at home improvement stores, absorbing moisture and what not. If you feel that it is fresh then use it. If you notice little clumps in the mortar while pouring this usually indicates that moisture has penetrated the bag. Return for refund.

The materials at tile supply houses are typically more fresher and thus reliable.

By the way I'm not a great fan of Custom's line of thinset mortars. I prefer TEC.
 
  #8  
Old 12-22-00, 07:02 AM
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Plywood

Froggyman,

Can you explain your comment "Remember to skim coat the plywood with thinset mortar as you work" ?
 
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Old 12-22-00, 07:08 AM
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Setting time.....

I am also curious about the setting time of thinset mortar.

I have read that I can grout after 24 hours and seal the grout after three days. No mention is made as to how long I should wait before placing a large amount of weight on the tile. How long must I wait before I can move in the appliances such as the refrigerator or install the cabinets ?
 
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Old 12-22-00, 09:10 AM
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Take the flat side of your thinset trowel and "smear" the section of the plywood with thinset before you apply the thinset normally using the notched side of the trowel . This will ensure that you have the proper mortar grip to the plywood.

You should be able to move the appliances safely back 24 hours after the grout has been installed. I would recommend that you place a 1/4" sheet of plywood over the kitchen floor tile first to help distribute the weight of the appliances.
 
  #11  
Old 12-22-00, 10:00 AM
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Thank You

Thank you for your help. Wish me luck........
 
  #12  
Old 12-22-00, 11:01 AM
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Foggyman,

I won't quibble about the diferences between latex and "polymers." I think you will find, however, that the Tile Council of America no longer accepts plywood as a suitable substrate for ceramic tile. I'm not saying I fully agree, but that's how it is. You can check with Dave Gobis, current director of the Ceramic Tile Education Foundation, under the TCA.

http://www.tileschool.org/

John
 
  #13  
Old 12-22-00, 02:20 PM
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You are wrong John and I do have the TCA Handbook.

See http://c-cure.com/servref/techsupp/105.htm for more info including install requirements.

I also suggest you refer to the Ceramic Tile Installers of America site. They provide more info on where plywood can be used. Pay extra attention to the LATEX additive recommendations.

http://www.ctioa.org/ctioa/newsletter.htm

[Edited by froggyman on 12-22-00 at 05:48]
 
  #14  
Old 12-22-00, 03:04 PM
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Okay, I've been wrong before, but I'm not going to continue arguing this point here. Since I can't seem to email you, how about shooting me one. Let's get acquainted.

John

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  #15  
Old 12-06-12, 09:01 PM
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Well Time is the best tester. Hows that floor holding up?
 
  #16  
Old 12-06-12, 11:09 PM
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I laid all the tile in my home 20 years ago on 1/2 in exterior plywood that was screwed down to the 3/4 in subfloor including bathrooms and kitchen. I never had a single tile pop. I did, as what was mentioned earlier however, flat trowelled the thinset onto the plywood followed by notching the same area before laying the tile. This insures a much better bond than just slapping the thinset on the plywood and using the notched trowel. I never filled in any joints in the plywood. Thinset just needs a little more help to adhere to plywood than a cenmentasious product but it will adhere if care is given. Having said all this, I would not do what I did again simply because using a cement board is smarter and more durable in general and it takes the same effort to use cement board as it does plywood. I simply got away with it and most prob will if care is taken but still it makes more sense to attach a cenmentasious product (thinset) to a cementasious product (Durock etc). If you were to get a flooded tile area, the latter would clearly be superior to the former. Lay 1/4" BB or Durock before the tile and live with a slightly elevated floor with some kind of threshold transition. It's worth the difference and people step over elevated areas between rooms all the time especially when the surface products are different... ie a threshold frequently is 1/4" to 3/8 " higher from one room to another. I believe in these recomendations so much that I am remodelling my master bath now (where a tile never popped) and I am unscrewing and tearing out the 1/2 plywood I had down 20 years ago and going back with 1/2 in Durock.
 
  #17  
Old 12-07-12, 02:49 AM
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This is a 12 year old post and no one involved is still active. Thread should be closed.
 
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