Newbie tiling a concrete floor


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Old 09-05-05, 11:45 AM
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Cool Newbie tiling a concrete floor

I plan to embark on my 1st tiling job - laying porcelain tile on a 28x12 lanai/porch (enclosed on 3 sides and open on the other). The concrete slab is currently covered with thin glue-down indoor/outdoor carpet which pulls up easily, but does leave a very thin coat of carpet adhesive behind (I've tried scraping it manually and it's going nowhere).

The floor is "wavy" in areas (i.e. not flat). The dips seem to be about 1/2" lower than the rises.

I'm looking for recommendations as to whether I should use self leveling compound to plane the floor, some other product to patch the lower areas, or whether those tolerances are acceptable for building up the thinset in the low areas as I lay the tile.

Also, I'm considering 18" versus 13" tile. I'd prefer the larger, but have been told it's easier to adjust for level using the smaller tile. Any thoughts on that?

Any advice would be greatly appreciated.
 
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Old 09-05-05, 03:50 PM
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Try soaking the adhesive with hot water then scraping it after a few minutes.

I would pour some self leveling cement to get rid of the ripples to a degree but please realize this will take away some of the pitch, if any, that exists to allow water to runoff away from the house.

If you can get the bumps out go with the big tile, if the washboard effect remains, use the 13".
 
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Old 09-05-05, 05:22 PM
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i had the same problem

When i pulled up my carpet in the sunroom, it had some of the adhesive still stuck to the concrete. I scraped it, washed it, and thanks to other jobs in the room i had to do, just by walking on it for a month, more came off. I got most, but not all of it off but i put down the self leveler and it worked well. The Self leveler is great because it makes a clean surface to do the tile on, plus i was told that the thinset for the tiles does not bond well to the adhesive. Especially since this is your first tile job (this was mine too) you don't want to be worried about trying to level the tiles with the thinset. It's hard enough laying down the tiles, cutting, and doing all the other parts of the job to make it look good.

Pat
 
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Old 09-28-05, 11:47 PM
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Back again...

Having FINALLY gotten around to pulling up the carpet, I'm back with more questions. First, yes, I'm able to scrape up the adhesive after wetting it. Should I presume there is 350sf of adhesive scraping in my immediate future?

After pulling up the glue-down carpet, I can see the uneven areas more clearly. I used a 10' 2x4 (the straightest one I could find). I slid it around on the floor and noted good sized low spots of 1/4" to 1/2" in various places around the slab. (This may be a "slow" question... but is that the correct method for checking the plane?) There seem to be a few larger areas where the slab is kinda "crowned" and the lower areas kind of fall off around them.

If it makes a difference, it's relatively flat parallel with the 12' width and wavy parallel with the 28' length. (Hoping I'm painting a clear picture here...)

Bob - how "flat" would I need to get the floor if I went with the SLC? It seems to me I'd basically have to pour it over the entire floor to fill in all the low spots. The area is under a roof, enclosed on three sides and screened on the other with no freeze issues - quite protected, but technically "exposed" to moisture. Is SLC suitable for this type of environment?

One problem is that there's a patio door leading on to the lanai. The lip on the bottom track of the patio door is less than 1/2 high, so I can't build up the height of the floor too much or I'll have a trip hazard when passing through from the house to the lanai. How is this typically addressed? Is there a transition of some kind made for this situation?

I know how much I don't know - and I'm trying to do a good job here - so I sincerely appreciate any knowledge and direction you all can offer.
 
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Old 09-29-05, 02:04 PM
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1.) Scrape on

2.) The 2x4 probably is not milled flat but it will give you a good idea of the floor variations.

3.) Is the porch door a slider or a french door that swings open?

Being that the porch is somewhat exposed to the outside and you dont want to raise the floor height too much you could take down the "high spots" by grinding them. The most costly but quickest and most efficient would be to rent a grinding machine that looks like a buffing machine. It has a grinding plate on the bottom to level off the high spots. It will create mega dust but the machine has a rear port that can be hooked up to a shop vac and that will collect most of it. A shroud on the front of the machine keeps it from escaping that way. This will give the added benefit of removing any leftover glue you cant scrape up.

Tileman is also an expert on concrete work and prep and if he sees this post I hope he will guide you further on what else may need to be done. By the way, can you see any cracks in the concrete?
 
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Old 09-29-05, 07:28 PM
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Thanks for the response Bob - the door is a slider. I see only one crack in the slab. The crack is very narrow, no gap between the two sides, runs all the way across the width of the slab and is flat across the top (one side isn't higher than the other. I can see that at some point in the past someone put some kind of patching compound on it. Has to have been at least 7 or 8 years ago, judging from the condition of the carpeting and the fact we've been in the house 4 years ourselves.

If I went with a grinder for the high spots, how level would I need to get it? Within 1/4", 1/8"? Does it take a long time to do? I'll check on the cost to rent one.

I did check on the cost of SLC today and I figure if I have an average of a 1/4" across the whole floor, I'm looking at $500 (too much) - so I think that option may be out.

Any other feedback, Bob? Tileman - are you out there?
 
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Old 09-30-05, 04:04 PM
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You will need to address that crack, I use this product all the time over cracks in slabs, there are others as well.

http://www.tiletool.net/Crack_Tile.asp

You can grind down the high spots as Bob suggested or just use SLC in the low areas without doing the whole floor, or biuld up the low spots with modified thinset, hard to say without seeing it, unless using large format tile, it doesn't have to be perfect.
 
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Old 10-01-05, 11:50 PM
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Thanks for the advice everyone!
 
 

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