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        Tiling Concrete Slab w/Saw Cuts Sign In/Join 
        posted
        Hi - I'm building a cabin and am to the point where I want to finish the floor. Its a concrete slab that is 3 years old. There are a few hairline cracks from when it initially settled. There are also saw cuts in it to control cracking when settling. They aren't real deep but they are maybe 1/8" or so wide. Everything is in plane. Plastic and insulation under the slab plus radiant heat. Looking to do a kitchen, livingroom, and bathroom all connected together, roughly 500 square feet.

        My question is, how would I handle the saw cuts and hairline cracks if I am going to tile over it? I saw products like Ditra but didn't know if that would do me any good in this case or if it was overkill. Plus I was hesitant if it would cause issues with the radiant heat. I don't think it moves any more or if it ever even cracked in the saw cuts (would have to look), never know though I guess. Any suggestions would be great!

        This message has been edited. Last edited by: Dan20,
         
        Posts: 4 | Registered: Feb 21, 2014Reply With QuoteReport This Post
        Picture of Jaybee
        posted Hide Post
        Adding a Ditra membrane layer will not hurt and will isolate some of those cracks - making for less of a chance that a crack in the slab will transfer to the tile.

        You can also do thinset and tile directly on the concrete slab.

        Both ways will work, both could give you a floor that never has any tile cracks. And both could see cracks happen. Adding the Ditra just makes that less likely.


        Jaybee
         
        Posts: 10326 | Location: Knoxville, Tennessee | Registered: Sep 27, 2003Reply With QuoteReport This Post
        posted Hide Post
        Hi Dan,

        I would make those cuts a little deeper. If memory serves, I recall the cuts should be about 1/3 of the total thickness of the concrete. 1/8" isn't doing you any good. If it settles, it's not necessarily going to break where it's supposed to.

        Those hairline cracks are probably shrink cracks, it happens as the concrete is drying. This can keep happening for a year or so. Sounds like the cracks are in plane, so probably no settling.

        Ditra and other membrane can handle hairline cracks and even larger. However, even with Ditra you still have to honor the control joints. Ditra is not overkill. It does not adversely affect radiant heating.

        Aside from Ditra, there are liquid applied membrane and crack isolation thin set mortars. For sure the area is large enough that you would have needed expansion joints, but you need them for sure, in the field and perimeter as always.

        There is one membrane product that will allow you to disregard the cuts so you do not spoil the tile pattern with additional joints.

        Research; Noble Company products; NobleSeal CIS http://www.noblecompany.com/Pr...efault.aspx#products

        It's a great product/system, only problem is it might cost more than the tiles depending on what you've selected.

        Jaz


        Tile 4 You llc - Troy, MI
        Kerdi shower specialist - Ditra installs - Product-Method suitability consultation. I have NEVER made a mistake, I thought I did once...........but I was wrong!
         
        Posts: 45 | Registered: Apr 18, 2013Reply With QuoteReport This Post
        posted Hide Post
        Thanks guys, this helps a lot. I was debating putting the tile right on the concrete, but this will be my first time doing a large area like this so I had to ask. I've built the entire cabin up to this point so I don't plan to stop now.

        The cuts are actually deeper, I wrote that poorly. They are just 1/8" wide or so, width of the blade. Normal cuts like you would see in a garage slab.

        Good to know Ditra won't affect the radiant heat, that was one of my concerns with it. The system is working so good now I didn't want to mess it up.

        I'm going to check into that NobleSeal, I like the idea of being able to keep my tile pattern the same.

        This message has been edited. Last edited by: Dan20,
         
        Posts: 4 | Registered: Feb 21, 2014Reply With QuoteReport This Post
        posted Hide Post
        Do you know about how much electricity you will be using for 500 SF..?
         
        Posts: 827 | Registered: Jan 29, 2010Reply With QuoteReport This Post
        posted Hide Post
        I'm not sure what you mean by electricity, are you referring to the radiant heat?


        I think I'm set on handling the cracks now. I talked to some others as well and they also mentioned NobleSeal CIS. I think I'm just going to use it over the cracks and saw cuts as its pretty thin. I was a little worried about the height difference at first when looking at Ditra, but NobleSeal is less from the sounds of it. I'm going to put it down using NobleBond EXT then, just keep it all the same company, less thinking for me Cool

        This message has been edited. Last edited by: Dan20,
         
        Posts: 4 | Registered: Feb 21, 2014Reply With QuoteReport This Post
        posted Hide Post
        One last thing I'm debating, since I'm putting my tile mostly on concrete, can I get away with using a modified thinset or would I need an unmodified? I want to get a premium thinset either way, just not sure exactly what type to go with. I see a lot more modified then unmodified at HD.
         
        Posts: 4 | Registered: Feb 21, 2014Reply With QuoteReport This Post
        posted Hide Post
        I don't see how the thickness of Ditra is relevant at all. It's 1/8" and goes on 100% of the floor.

        You can use NobleBond EXT, but can't figure out why when you can use modified thin set.

        As for the type of thin set for the system. Aren't the tiles porcelain? You have no choice. Tell us exactly what tiles you're using.

        Jaz


        Tile 4 You llc - Troy, MI
        Kerdi shower specialist - Ditra installs - Product-Method suitability consultation. I have NEVER made a mistake, I thought I did once...........but I was wrong!
         
        Posts: 45 | Registered: Apr 18, 2013Reply With QuoteReport This Post
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