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Unread 03-01-2007, 09:54 PM   #1
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Ditra Issues in Houston

Harry Dunbar sent me over here. His forum is excellent, but this one is a little closer to home. I live in the Houston, TX area and I've never installed tile in my life. It looked pretty easy when I first thought to do this project, but now that I'm getting into the details, it's getting a bit intimidating. I plan to install 13x13 and 18x18 porcelain tile over a concrete slab (more than ten years old). So far I don't see any cracks in the slab, but I've only pulled up 32 sq ft of vinyl so far in a bathroom. But being a paranoid type of person, I thought installing Ditra would be a good idea. We plan to stay in this house for a while, so I want to do a good job that will last. However, when I went out to buy some Ditra, either the dealer had never heard of it (Home Depot for one, even though they display it in their store), or was told I don't need it ("it's overkill"). Some dealers even said that unless I have a wood floor, I don't need Ditra. So, my question to the more experienced folks here is: is Ditra a good idea to make the installation "bullet-proof", or is it something I don't really need in my situation here in Houston?

My wife wants this project to get going soon. So my alternative is to just use flexbond and get going. Home Depot pushes versabond pretty hard, but my take form this forum is that flexbond is better. Anys thoughts on that?

Thanks to all for all the great advice I've seen so far.

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Unread 03-01-2007, 10:12 PM   #2
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Scott, it's late, so bear with us in getting someone over here to help you. And welcome to the forum. Glad you are here and hope we can help!
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Unread 03-01-2007, 10:36 PM   #3
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Hey Scott, although I'm no expert on Ditra, I use it a lot and think it's definately not overkill. Here is why; Concrete can shift and crack at any time, through movement or settling. The ditra acts as a crack isolation membrane so it will prevent the tile from cracking with the concrete. It also acts as a moisture barrier, releasing moisture through the groves out to the sides (another reason to leave a space around the outside). Just remember to use the recommended thin-set. I think in your case versabond underneath the ditra and an unmodified between the porcelin tile and the ditra. Maybe some others will chime in if I'm wrong but I think that is OK as long as the concrete absorbs the moisture from the thin-set. A moisture test will answer that ?.
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Unread 03-01-2007, 10:47 PM   #4
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I'm not surprised HD doesn't know about. They don't carry it here in Austin.

Overkill? maybe but only time would tell. If you can stomach the extra money and a little extra labor it will definitely be cheap insurance.

From an installer's standpoint, I would only try to sell it if the slab had alot of cracks. If I only saw a few cracks( as is typical) I would use Redgard instead and save the money and labor. Keep in mind that neither will address vertical slab movement.

Actually, if I saw alot of crack I'd sell 'em carpet or laminate

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Unread 03-01-2007, 10:52 PM   #5
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hi Scott - just a DIYer here who just finished a little Ditra on an older slab. Here's what I learned.

buy yur Ditra from Dave at Tile-Experts. Best price, fast delivery, and you can even call him for questions if you can't get answers here. Homer's price is high and he makes up for it by forcing you to buy more than you need.

for slab Schluter says unmodified on both sides. Lots of folks here use Versabond successfully. Don't use anything more modified than Versabond. I used Kerabond (unmodified) and really liked working with it. Make sure you get the gray for under the Ditra. White blends with the fleece and makes it hard to check coverage.

Ditra or no, you should definitely do the water test on the concrete before starting.

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Unread 03-02-2007, 12:03 PM   #6
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I guess my frustration comes from knowing Ditra is a good product (from listening to all you guys), yet the dealers on my side of town (Clear Lake area of Houston) are falling all over themselves telling me I don't need it (and don't seem to want to sell it to me). I'd like to hear from some folks who have done tile jobs in the Houston area. Am I crazy to want to install Ditra on a good concrete slab in Houston? These local dealers seem to think so!

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Unread 03-04-2007, 05:57 PM   #7
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How do you check level on a concrete slab?

Sorry to start a new thread, but this is a totally different question. Does anyone have a specific method for checking level on a concrete slab? I'm having trouble with this, determining where the low spots are. It seems to me that it is highly dependent on the reference point where you started. It can't be this difficult, can it? I just need some very specific instructions on how to do this.

I'm installing 13x13 porcelain tile in a 32 sq ft bathroom. Yesterday I poured some SLC, but I think I made the problem even worse. After this project, I plan to install 18x18 porcelain in a kitchen.

How level does the slab have to be for these tiles? I've read 1/8 inch over ten feet, but that seems pretty tight of a spec. Thanks.

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Unread 03-04-2007, 06:21 PM   #8
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Hi Scott,

You're not really concerned with whether the floor is level. All you need is a floor that's relatively flat. You can determine flatness with a long straightedge, something like an eight-foot 2x4 will work.
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Unread 03-04-2007, 06:30 PM   #9
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becareful with a 2x4 alot of them have whoopy de doos in them. i would opp for a peice if 1x4 in the select pint isle its like 4 bucks but its alot better than a 2x4.. But JOhn is rite the key to a floor is FLAT not always level.
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Unread 03-04-2007, 06:53 PM   #10
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Howdy Scott,

Sorry to start a new thread, but this is a totally different question.
But it's the same project so's the info on the other thread is pertinent to all your discussions..

Yesterday I poured some SLC,
How much out of flat is your floor? Did you do the straight edge test like John n Dan suggested?
A 4' level should work for the width and can tell you a little about the long run too... If you're lookin at 1/8 " over the length it should be no problem..
Try to describe the topography of the floor...

I've read 1/8 inch over ten feet, but that seems pretty tight of a spec.
You'll appreciate the tight spec while you're setting...

When you go to the 18"x18", it will be a little more important....
mm (aka "Paco")
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Unread 03-04-2007, 08:08 PM   #11
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Hi Scott, I merged your thread with this one you started. We like to keep all the questions for the same project on the same thread so others can follow it. Just save this to your favorites reply on it and it will go to the top of the page.
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Unread 03-04-2007, 10:05 PM   #12
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Thanks guys, for all the advice.

I do have a 48 inch box level that I have been using. There does appear to be areas on the floor that dip more than 1/8 inch. The room is 5' by 8', with a 19" by 4' vanity taking up one corner.

At this point, since it is such a small area, I'm thinking of pouring LevelQuik RS over the whole area. Good idea or bad? I already made two spot pours and I think I made things worse. I've never used SLC before. I think I goofed and poured it on a high spot. But wouldn't it have just run off?

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Unread 03-04-2007, 10:33 PM   #13
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To check the surface's topography I used a water level, a 50' length of clear plastic tubing filled with water and a little food coloring. The length can be adjusted for the size of the area being measured. Tape one open end, along with a short ruler, at eye height,to a 6' piece of conduit. Tape the other open end to a column somewhere, or a wall, at a height of about 6'. Place both ends next to each other, with the conduit resting on the floor, and take a reading on the ruler of the height of the two equal water columns. You can add or subtract water to some convenient measuring point on the ruler.This is your reference point. It can be located anywhere on the floor. Get a piece of graph paper and move the end with the ruler taped to the conduit around the floor, taking reading every foot or so. Keep the conduit vertical and one end resting on the floor for each reading. The more readings you take, the better the picture. My ruler was calibrated in tenths of an inch. Each square on my graph paper represented one square foot. I would just write a single digit in the particular square foot that I was measuring, I.E., 2 for 0.2", 3 for 0.3", ect. I then colored all my 2's red, my 3's orange, my 4's yellow, ect. and also counted up the number of squares associated with each number. The number with the largest number of squares associated with it would be the mean height of the surface. This will give you a very accurate visual topography of that slab.

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Unread 03-05-2007, 10:15 PM   #14
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Need help, please

Should I just use LevelQuik RS over the whole area to assure it's flat? Does anybody have experience with this product? Can I use LevelQuik over the other smaller spots where I poured a one-part SLC already, or will there be bonding problems there?

Can I tile right over the SLC after it has hardened? Custom's instructions say you can tile after 4 hours. But isn't LevelQuik a portland cement that needs 28 days to cure?

I really need some expert advice here, guys, as I feel I'm in over my head right now. Thanks.

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Unread 03-06-2007, 12:31 AM   #15
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I've used a quicklevel product only once and it was rock hard in only a few minutes. Cement doesn't need air to cure so it can still do that under the tile.
If it says 4 hours on the package it's likely correct.
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