Ceramic Floor Tile Problem - HELP!

[bigeck]

Hi folks,

I wonder if anyone can help me with this please?

I have a concrete floor on which I was going to lay porcelain floor tile but as it is uneven (I can fit a pencil under some corners of a few tiles - so they rock) I decided to lay SLC first on the side of the floor that was uneven. I mixed it as per the instructions (even measuring the water with a measuring jug to prevent overwatering as I've never used SLC before), unibonded the floor as per instructions and poured the SLC. It's taken longer than they said it would to dry because I have no heating as it's being altered but when it did dry it all appeared okay. Unfortunately today (probably 10 days since pouring) when I was looking at it prior to tiling, it has massive hairline cracks through it and it sounds hollow if you knock it. It appears it hasn't bonded to the floor and I managed to lift a lot of it by getting my fingernails/screwdriver under it and lifting it. Can't imagine this is how it should be so I wondered if anyone could advise the likely causes and remedies? Also am I correct in doing it this way or could I just lay the tiles (using professional dry powder - not ready mix) and use the mixture to take up the uneveness as I've been told by some folks the professionals would do/have done to theirs?

I'm a very proficient DIYer but this has got me stumped as I'm not sure whats going wrong - especially as I've followed the instructions to the letter.

Any help from anyone would be much appreciated as it's got me scratching my head.

Thanks

[OttoMan]

................................ Hi folks,
I wonder if anyone can help me with this please?

Wish someone HAD answered you, been hanging-around ever since you first posted this! :D

I had a similar problem? Not a badly finished concrete floor, just needed a bit of care when laying the tiles due to some un-evenness? After a few weeks, (I had used a good quality self-mix adhesive on the tiles but did not use any floor leveling) Started to notice a few 'rockers' and when taking the tiles up, they came complete with a suitable layer of adhesive!! No apparent reason for this, given I had put a few layers of PVA (mixed at 4-to-1) on the floor?
For whatever reason, I found a fair bit of damp underneath every tile I removed! Can't recall dropping water on the finished floor but the problem appeared to be some kind of rising-damp?

My eventual solution? I binned the old tiles, ripped-up the concrete floor, replaced the damp-proof membrane, finished the (good level) concrete floor. After a few weeks, put down about 3 layers of PVA (Unibond at 4-to-1 again) and 3 weeks ago, finally re-laid a new set of tiles!!
Cured? Not sure! I guess time will tell if I have wasted another bucket of money! I sincerely hope not!! (Hope this helps mate, it drove me NUTS!!)