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07-03-2008, 06:45 AM
I 'm a handy do it yourself guy who is doing my first tile job. The job is my basement 750 sq. ft. over radiant heat in poured concrete family/bathroom/laundry room area. I have several questions. I have two saw cut control joints in the slab do I need to patch them with a floor leveler? I have one small crack due to concrete shrinkage. I was going to go over the whole slab with Red Gard waterproofing and crack prevention membrane, is this enough? Which brings up my next question the slab was sealed five years ago when the house was new with a cheap menards concrete sealer. I did a water test and poured a cup of water on the slab and let it stand a few minutes and when you dry it off it leaves a darkened spot were the water was. Do I still need to etch the concrete or strip the sealer off before I install the membrane. My next question is being the floor is radiant heated how often should I put in an expansion joint in the floor? I'm using 12"tiles spaced 3/16", using 1/4x1/4x1/4 notched trowel with Flex Bond fortified thin-set mortar and sanded grout. Because of cost I wanted to see if the job could be done without using Ditra. Any info would be greatly appreciated. Thanks jojo2.

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07-03-2008, 07:01 AM
1. I would leave the control joints open and free of debris. Place mesh or fabric over the area and stick with Redguard.
2. Put the mesh or fabric over the crack if it's large; if it's just a hairline crack you can proceed with the Redguard.
3.Redguard is a good, proven product. Read the directions and follow them and it will be enough.
4.If the water just sat on top at all instead of soaking in, yes it needs to be mechanically removed. Chemicals are a bad thing. They can pull the sealer into the slab more making things worse. If the water soaked right in it won't be as critical to remove. Don't assume that just because the materials came from a big box store that the item is not good, we buy stuff there all the time. We just know what's good and what isn't.
5. I don't beleive the radiant stuff changes expansion placement because the heat is constant; unlike exterior where the temperature varies up and down. I'm in Fl. though and we don't use fancy stuff like that. Someone should correct me if I'm wrong. Typical placement of soft joints is 20-25 feet. But you should put caulk joints over your control joints. Line up your layout over these if you can, or close to it.
6. I'd suggest a 3/8" notch.