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Old 05-01-2010, 05:45 PM   #1
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Concrete floor prep for ceramic tile


I am installing a sun room (frame & glass) onto an existing covered porch.
Issue 1: The original concrete slab against house is properly sloped our toward yard, but an additional slab adjoining it between the house slab and yard is level. Let's call them the "house slab" and "additional slab". Thus, there is no contiguous flat plane across both existing slabs. The "additional slab" could be removed, but to pour a new one on same sloped plane would put it below ground level.
Issue 2: The "house slab" apparently was poured under the brick walls (3 sides). Removing the slab could damage the brickwork.
Issue 3: Only 2.25" (highest spot on "house slab" to expected top of finished concrete & ceramic tile floor) is available to work with. Back off the ceramic tile, bond, and probably some membrane and what is left is about 1 3/4".

Problem: What is best solution to build the subfloor for laying the tile?

Some solutions I though about:
1. Leave everything as is and endure the slope to flat surface, placing a grout line across the line of change. This would require me to do a simple tile pattern rather than one I desire (not straight grout line)
2. Over pour it with another layer of concrete with thickness of 1 3/4 at house increasing to 5 1/4 inches at yard edge (well, will actually be sun room wall then). Lay antifracture membrane (Ditra) and tile.
3. I read the typical minimum over pour should be 2". I could do this except for a 2' wide section parallel to inside door, lay tile on the main floor over the over pour, then (no 45-degree angle fom main floor), transition the last 2 feet over a MUD base on a decline to the door (about 5/8").
4. Go ahead and bust out both slabs, pour floor as requied, and repair any brick damage (or whatever?).

Do any of these make sense? One local builder said he'd never tile over an over-pour. Comments. Thanks ahead of time.

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Old 05-02-2010, 04:25 PM   #2
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Concrete floor prep for ceramic tile


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1. Leave everything as is and endure the slope to flat surface, placing a grout line across the line of change. This would require me to do a simple tile pattern rather than one I desire (not straight grout line)
This should be acceptable in most cases. If the current "cement joint-line" is not straight it may be possible to lay the tile in a straighter fashion by slightly lapping the underneath cement joint as needed. Keep in mind you cannot use grout in that grout line. Use a flexible caulk there.

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Old 05-02-2010, 04:45 PM   #3
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Concrete floor prep for ceramic tile


I appreciate your opinion. The Sun Room contractor was planning to pull up the outer slab since it was a shady pour by previous owner and not reinforced into other slab (just a hair higher to along the adjacent edge) -- footings also need to be poured under new slab. He said he'd pour level to inner slab edge. I guess I can do something artistic, a transition, along the line and return to the pattern I desire on both sides. Line will be in the middle. I'm sure the grandkids will enjoy the slope so they can roll their balls into the glass front -- lol. 1 vote for endure the slope change.

Bud, did you find anything wrong with other options that would scare you away from doing any of them, like work effort, cost, subfloor cracking, appearance, etc.?
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Old 05-02-2010, 05:41 PM   #4
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Any "over-pour" would be susceptible to cracking caused from the seam below. Two inches won't change that real possibility.

The highest hope for lasting success would be to remove it all and re-pour it all using steel rebar reinforcement. The thing is...that may be a cost that you don't want.

If the extension that concerns you is really hokey then redo just that section. Keep in mind that any seam (joint) between the two slabs still would have to be honored through the tile.

I have seen good success using the first method.
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Old 05-03-2010, 08:16 PM   #5
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Concrete floor prep for ceramic tile


Bud,
Appreciate your suggestions. I will ensure the contractor pours a new slab that is reinforced and anchored to other slab meeting at same height. I will ensure he defines the control joint between them to be absolutely perpendicular to existing control job in first slab. Then I lay 6" tiles along both joints over ditra using flexible grout directly over the joints. Guess I got a little too focused on the changing of the slope to level slab. Probably won't even be noticed. Thanks.
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Old 05-05-2010, 06:33 PM   #6
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Concrete floor prep for ceramic tile


Bud...may I ask your opinion again? A different contractor recommended laying a 1/8" cement board over the concrete floor room. It would not be glued down; hence, float. Would this be an acceptable substitue for Ditra which he said is costly.Any implications of this solution over time compared to laying directly on concrete and thus honoring the control joints via a ditra-like membrane over the joints and flexible joint over control joints? I take it with the concrete board he would use only grout between tiles. Your help is always appreciated.
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Old 05-05-2010, 07:03 PM   #7
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Quote:
Bud...may I ask your opinion again? A different contractor recommended laying a 1/8" cement board over the concrete floor room.
I have no idea where you people find these guys! My first question is...where are you going to find 1/8" cement board? Is it available in your area? I've never seen it and I'm not sure it even exists.

Quote:
It would not be glued down; hence, float.
That suggestion is even farther off track. In the first place cement board is weird stuff, it is irregular and is generally warped. It is ALWAYS installed with fasteners for this reason and it is ALWAYS installed in a bed of fresh thinset. It is NEVER used over concrete. Those are the manufacturers recommendations - not mine.

Quote:
Would this be an acceptable substitue for Ditra which he said is costly.
You've got to stop reaching into the bottom of the barrel to find these low-budget guys. "COSTLY" in what way? Sure it costs more than cement board because they are two entirely different products with two entirely different purposes!

Pickup trucks cost more than garden tractors. Why is that I wonder?

Quote:
Any implications of this solution over time compared to laying directly on concrete and thus honoring the control joints via a ditra-like membrane over the joints and flexible joint over control joints? I take it with the concrete board he would use only grout between tiles. Your help is always appreciated.
You better look for a different contractor - find one that knows what he's talking about next time, this guy doesn't have a clue.
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Old 05-05-2010, 08:17 PM   #8
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Concrete floor prep for ceramic tile


Thank you again Bud. I read enough about this approach before this guy suggested it and had my doubts big time. I was hoping to get an answer like yours to confirm my uneasiness. This was the contractor who would have removed both slabs and brick walls, pour new floor level, and dry wall entire room. This was satisfactory, but wife wants the brick (he claimed he could repair any damaged brick after floor demo, but that made me uneasy too). So, I guess he's trying to match some job he did in some bathroom some other place -- I did subflooring in one long ago. But this is first time I heard of floating board above the concrete. Anyway, Not gonna do it that way. I respect your opinion. Got your blood warm even. I'll pay the cost now. Which leads to this question:

The antifracture membrane. Given two control joints perpendicular to each other, I assume I'd cover those. I also have hairline cracks, very aged, not close to a control joint depths, but several across half of my inner slab that will remain (never cracked at control joint). Do you think I should membrane these too?

The Sun room contractor (not the same as the one who suggested concrete board) mentioned some thinker orange membrane. He said I could always cover the entire floor and tile on top. He did not know the name of it. Do you happen to know what he might be thinking of and whether covering the entire floor would provide any benefit. Thanks again Bud.

I just checked the price of Ditra at Home Depot...No problem. Only question I have is entire floor or not. Anticipating your answer, I'm ready to do entire floor..lol. So, please guide me on necessity for expansion joints in tile surface for a 12x12' room. Necessary? I don't want to clean out the piggy bank if I don't have to. I assume when I read about them, they might be referring to the flexible caulk rather than grout along walls? Or just concrete control joints under tile?

Last edited by tpanc13; 05-05-2010 at 10:06 PM. Reason: Extra research and related question
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Old 05-05-2010, 10:43 PM   #9
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There are only two "orange" membranes on the market that I am aware of. Both are Schluter products. DITRA is the one you know about and KERDI Mat is the other. KERDI is a waterproof membrane mainly for showers.

Schluter offers mechanical joints also. They are pretty nifty but very costly and in this case unsightly I would think.

Your dimensions of 12' X 12' are inside the envelope as far as I'm concerned and normally wouldn't require an expansion joint. If it weren't for those pesky slab junctures. If you use a "sanded" caulk to match the sanded grout color you use those junctures won't be all that noticeable. I've done soft joints that you couldn't tell weren't rigid grout.

The joints along the walls also should not be grouted. You need to maintain some flexibility there also. The color-matching caulks can get pricy also but again I think they are worth the money in this case.

You should maintain a 1/4" gap at the house wall (if I'm following this). That gap 1/4" wide will swallow some caulk however. If there is already a bottomless crack at the house use some cheap exterior caulk to seal-off the abyss. Then use a pourable urethane caulk to partially fill the gap on top of the cheap caulk. THEN (finally) you can use the color matching caulk to top it off. This method will save on the amount of expensive caulk you will need.

I wouldn't worry about the small cracks as long as both sides of the crack are on plane. DITRA will take care of them for you.

NOW, the one juncture (cold joint) between the two separate slabs...I think you said it meandered a little? When honoring a control joint such as this the joint doesn't always have to be exactly above the cold joint. In the case of a meandering joint it is possible to sorta average the joints position under a straight grout line. Then soft-joint the gap. This way the tile looks as it should and the joint (down below) can do its own thing. Keep in mind there are no guarantees with this method but again I've done it and seen it work many times. Just don't get too far off [away] from the offending joint.

A picture would be nice.

Hope I haven't confused you. If so...I can try again if you want.
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Old 05-06-2010, 08:10 PM   #10
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Bud..you've been a tremendous help. You have the right picture and answered everything completely. My discomfort originates in my lower back, hence I thought I'd see if I could find a contractor (general) to bid the job along with raising my porch ceiling. I agree with you that the general contractor led me down the wrong path when I was already on the right path needing a push to the finish line. I think I'll take on the challenge of bending and do it all myself. However, the last uncertainty is the type of tile cutter (within a 1-job price range) I should buy or rent. I'd be using 6" ceramic tile and will probably have about 96 cuts at the most. I have several tile cutting blades left over from years ago for a recirculating saw -- If I remember correctly, they didn't last very long (I had a very small area then and used them because the extremely small town I lived closest to only had a very simple apparatus that was worthless). Another great answer from you will put on the top of my list (already there). Thanks.
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Old 05-08-2010, 10:39 AM   #11
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I don't know about "another great answer" but I will add that not too many years ago (8-10) saw blades of this ilk were very reliable but you got what you paid for back then and the good blades weren't cheap. Now days, the market has been flooded with crap. Blades are labeled for all purpose as well as specific use but you can't depend on most of them to be anything more than Frisbees. Try skipping those useless blades over a local pond and watch them skip repeatedly before they sink. There is great pleasure and satisfaction in that activity. Ah-h-h-h, but I digress.

Some (not all) porcelain tiles lend themselves nicely to being cut using a "score and break" type cutter. The glazed porcelains are the best for this. The unglazed...not so much. Unfortunately a wet saw is the only reliable method and even then some tiles will break anyway when you least expect it.

If you live remotely I might suggest that you install everything except the cuts. Then go where you have to go to rent a legitimate tile saw to make the cuts all at the same time. One days rental should do the trick in your case. The low cost budget saws may work for you but most of them are of such poor quality they really aren't worth the eighty (or so) bucks they cost and they don't skip well over a pond, they just immediately sink to the bottom but probably make good fish-habitat.

You might try Craig's List. Maybe you'll spark someones interest that has a better saw sitting around collecting dust and would sell it for cheap.
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Old 05-08-2010, 10:51 AM   #12
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I still love reading your posts Bud.......

You should open up a school, and teach this stuff.....
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Old 05-08-2010, 10:54 AM   #13
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yummy,

Any tiling going on at your place these days?
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Old 05-09-2010, 12:17 AM   #14
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You're the man Bud. When I last visited Lowes I saw an electric dirty usable saw in the aisle, but couldn't find anybody in the department who could definitively tell me if they would cut tiles for me and the price. Some gal told me it was free, but I doubt it. I like that idea though; however, I might give the score & snap tool. I appreciate you comparing the porcelain vs other tile re success with this type tool. I'm ready -- all I need is the Sun Room contractor to get front here and installed. Will let you know the success. Thanks once again. Next time I go out fishing, I'll take those old blades and see what distance I can get out of them.
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Old 05-09-2010, 09:58 AM   #15
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Originally Posted by Bud Cline View Post
yummy,

Any tiling going on at your place these days?

No tiling going on. But I am contemplating on installing some glass tiles behind my pedestal sink in my powder room. From the floor all the way up to the ceiling. About 2 1/2 feet wide.

I don't know if I can do a good job though. So I am still delaying it. Unless I can come up with another solution, as the area behind the pedestal sink becomes ruined with water, dents, etc. I hate looking at it.

Bud you are the man......

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