Ceramic tile on concrete

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Old 11-01-08, 11:01 AM
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Ceramic tile on concrete

I've searched and haven't found an exact situation like mine. I have a 18'x40' walkout basement that I want to tile with ceramic. It is 20 years old, dry and flat, with only a few spider cracks - no level difference across the cracks and they seem to be old cracks (they haven't enlarged in the 2yrs I've owned the house). Just a few cracks mind you - overall the floor is very stable and in great shape. The space is heated and cooled, and will see alot of traffic. I've done alot of tiling in my life, so I'm comfortable tiling this floor, but unsure about the specific questions:
Do I need Ditra?
Do I need an expansion joint in the 40' span?
Thanks!
 
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Old 11-01-08, 11:42 AM
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Welcome to the Forums!

Adding Ditra is basically like a insurance policy for your floor. If you can afford the added expense, I'de say go for it.

I believe you will be fine with tiling directly to the concrete with a decent modified thinset, like Versabond.

You should have an expansion joint around your 30' point.

What's the moisture level like? Could you tape down a piece of plastic, leave it there for 24hrs, and see if there's moisture build up?
 
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Old 11-09-08, 06:09 PM
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OKC, thanks for the reply. I did 3 moisture test areas this weekend - all 3 were dry after 48 hrs - I'm thinking I'll pass on Ditra... I also measured more accurately - the room is 18'x35' - ocan I get away without an expansion joint? Thanks again for the expert advice, Ken.
 
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Old 11-09-08, 08:03 PM
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You probably could get away without one, it's really your call.

Just don't use anything that comes in a bucket for your thinset, and don't get HD basic unmodified thinset (CustomeBlend).

Like I mentioned earlier, Versabond from HD or a Mapai product from Lowes.
 
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Old 11-10-08, 12:11 PM
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I think you need movement joints. Here's a link to TCNA where movement joints are discussed. EJ171 as referenced in the TCNA handbook suggest movement joints for interior at 20' to 25' in each direction. If direct exposure to sunlight, the recommendation is 8' to 12' in each direction.
 
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Old 11-10-08, 06:36 PM
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Thanks guys - I really appreciate the advice and sharing your knowledge... Ken.
 
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Old 11-11-08, 06:41 AM
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Here is the link. Sorry about that.

TCNA - Technical Services: FAQ
 
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