Schluter- Ditra or Backer Board

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Old 09-23-09, 05:27 AM
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Schluter- Ditra or Backer Board

Iím installing porcelain tile, sizes 18x18; 12x12; and 6x6, in my kitchen. The current floor is a plywood subfloor with linoleum at was installed in 1999. I have considered the product Ditra, but Iím not sure if it worth the money? Does anybody have any advise on Ditra, or is backer board the better choice?
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Old 09-23-09, 07:15 AM
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I've used a lot ditra as well as a lot of cement board over the last couple of years. Ditra is more expensive, maybe, but its easier to install. When you consider the cost of the cement board, the screws, mesh tape and the time involved to handle the cement board, the costs are probably similar. Both ditra and cement board will do the job.

You should know that either way, you need to remove the linoleum and any 1/4" underlayment before you go any further. Thats a must.

Another concern that you should have is that you are stalling some pretty large format tile there. This requires that you have a very stiff joist structure and very flat subfloor. If the floor is at all bouncy you'll wind up with cracked tile and grout. If its not dead flat, you'll wind up with some major lippage in the form of trip hazzards.

What size are your floor joists, what is their on center spacing and what is their unsupported span? What is the condition of the floor joists, are they in tact or hacked up with plumbing pipes running thru them. How thick is the plywood subfloor and how many layers of plywood are there?
 
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Old 09-23-09, 05:45 PM
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Thanks for the information.

The size of the floor joists are 12" engineered I beams, that are in tact. They are are 19" on center. with a unsupported span of 18".
I do not know the thickness of the floor or the amount of layers. I would think that the sub floor is standard construction.
 
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Old 09-23-09, 09:25 PM
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OK, sounds like you have I-joist that are 11 7/8" high spaced at 19.2" with a span of 18', right? If so I believe the floor joists system meets L480 at 40/10 live/dead load. Your subfloor should be min. 3/4" exposure 1 t&g plywood.

The L480 joists deflection is below the max allowable deflection of L360, so "below" is good. The things I don't like are the 40/10 load rating & the 19.2 spacing. However, because of the L480 rating, I believe you will also be safe on the weight load rating since porcelain is OK even at L360 as mentioned. So I'm OK with that part.

I'd like to see a double layer of plywood with anything over 16" spacing, but many homes at built that way today and some CBU manufacturers and Ditra, recommended their products in those instances. So, you're good there too, but I highly recommend going with Ditra instead of a backer board. Ditra is more forgiving, easier and yes more expensive, but worth it for sure.

Jaz
 
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Old 09-24-09, 07:21 AM
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I'd like to see a double layer of plywood with anything over 16" spacing, but many homes at built that way today and some CBU manufacturers and Ditra, recommended their products in those instances. So, you're good there too, but I highly recommend going with Ditra instead of a backer board. Ditra is more forgiving, easier and yes more expensive, but worth it for sure.
I'd like to see another layer of plywood as well. 3/4" over 19.2" centers is bare bones minimum with regular ditra and those are some big tile at 18". Adding another layer of 3/8" plywood (1/2" even better) would be a really good idea. I'm with Jazman on the recommendation of ditra here as well.
 
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