It is right by the shower. The shower is not leaking in any way. I think it is just where the former owners would exit the shower and whatever drips came off of them and were left on the floor make it right to the same spot. So im hoping by raising that area again that the water would pool away from the wall if left on the floor for any reason. Its not that I make a habit of leaving large amounts of water on the floor. I also thought of putting a bath matt at the shower entrance. But just in case the kids run out of the pool and leave water all over the floor (not like that would ever happen LOL) I would like to try and prevent it now while the tiles are being redone. One more thing it is a concrete subfloor. Thanks, Robert Robert

First of all, you still haven't specified whether your floor is "not flat" or "not level." Whatever else you have (or have not) done to get where you are, it would help a lot if you could say whether your problem is level or flat. Also, just to be sure here, if I am understanding you correctly, you installed the 2x4s ACROSS the 2x6s that make up the underside of the house? (Notice the very very NON-technical terms...so be aware that I'm not a builder or knowledgeable in this stuff like some of these people that post here...just sympathetic to rising note of panic in your posts....) The only reason I'm trying to clarify that is because I am wondering whether you installed the 2x4s "upright" (so the "4" dimension is vertical) or "laying down". I'm not trying to pile on to what you have *already* done, but I don't know what the proper distance for SPANNING that 2x4s have, and I don't know whether they can span two full feet if they are flat. This makes a difference because you want to install tile. If your subfloor is bouncy or bends ("deflects" I think is it), then all the tile you install will just crack and plague you and your heirs until the end of time...until you rip the whole floor and subfloor out again and re-do it. Or put in linoleum. Whichever comes first. You say in the top post that the cracks are like 1/4", but in your last post you write that they are up to 1". That's a big difference? Which is it? Does it vary from 1/4"-1"? Have you actually measure or are just eyeballing or going from memory? IF YOUR CRACKS ARE VERY SMALL: IF it were me (and it isn't), I'd probably just put down a very tight layer of Wedi board (thinset and screws/washers), seal the seams so it can hold the next layer, then put down a thin layer of self-leveling compound (though you still haven't said whether your floor is wavy or slanted), and then tile. IF YOUR CRACKS ARE 3/4'-1": Maybe use a layer of plywood (which would be cheaper but harder to cut), maybe tape and thinset the seams (ask someone on this board about this because I'm just brainstorming here), then use the SLC, then the tile. Only plywood will actually help form a floor (which I think you need to do with 1" gaps), not backerboard of any kind. Instead of Wedi, you could use probably any backer board (ask someone here what to do for the seams). But I only know about Wedi because that is what we went with, and I like it because it is light weight (good if you are a female working alone). I don't think your solution is in one step. It feels like you are going to have to create a tight subfloor, THEN level or flatten. I think you have a non-standard thing going on there, and that might not be addressed so easily with just one step before tile. One more thing, just out of curiousity, WHY do you think your floor must be level? Oh yeah, and I would start making your peace with a threshold. Given how non-standard your set-up is, AND the fact that this is DIY (or at least the subfloor), I'm not sure it is realistic to think you can get away with no threshold.

The manufacturere of my Mom's floor product recommend "Ardex" or "Mapei". They also recommend something with a compressive strength of 3500 PSI or greater. This was in part to level the slab and also to cover the old adhesive. I oversaw a gallery renovation where we wanted sealed concrete floors so we had to grind them down - messy and not fun. I can see why you might need to take down the hump but overall levelling by grinding the slab would never be my first choice.

Oh wow! You have some BIG questions that require BIG answers...for each one. First, concrete slabs are expensive to level...but you want to do it, so you will want to know what you are about to pay for. 1. Levelling concrete subfloor/slab (average...can be higher or lower depending on a gazillion things): $2-$5/sf. The age of the slab, how badly it is in need of repair, giant cracks, shifting soil conditions, etc, etc, etc. All of these things will add up to higher costs. So be prepared. I've known old slabs (from the 70's and EARLIER) to cost $4/sf without blinking. The really old slabs (20's and earlier) can take much more money to deal with. 2. The sagging subfloor underneath the room with the two king beds (wow...that's a TON of weight in one space...and I mean a TON). Whew...where to start where to start. OK. The 1/2" is big enough for you to LOOK UNDERNEATH the plywood (that means looking from underneath = open up ceiling below) to ENSURE you have wood joists that are SOUND. The deflection rating can be looked at BEFORE you damage your ceilings, etc etc etc. Is it possible to add new plywood to this room? Yes...but then you have to do it for all the subfloors on that level. Cost of plywood has quadrupled in the last 12 months. Which means the $1/sf stuff is now $4/sf. Ouch. Can that room be levelled using patch? Yes. It will cost around $2/sf for that room alone. 3. Moisture barrier...is something you put UNDERNEATH your floor to prevent the moisture BELOW THE SLAB from coming UP INTO THE FLOOR. It has nothing to do with bathing suit splashes dropping DOWN onto the wood. Nothing. So I'm not sure what you are asking in this one. OK...that's the 'most information' using the fewest amount of words. As you can see, everything depends on what BOTH subfloors look like when you REMOVE all the current flooring and 'start over'. I'm not fond of contractors who do NOT recommend using self-levelling over a wonky concrete slab. It tells me they KNOW it takes work to get it to work...but they have had PROBLEMS in the PAST with their guys doing the work PROPERLY. Which tells me they are all about doing everything as fast and as painlessly as possible (for them). They probably are NOT happy when forced to do things 'slowly and carefully'. Besides, they have probably BID other jobs with the $4/sf subfloor costs and been LEFT WITHOUT WORK. So they stopped bidding properly...which gets them work, but the results are less than stellar.