Please help. My wife and I did most of the work in renovating our apartment, and encountered only one seemingly unsolvable problem. The kitchen floor fell about 1 ½ inches from the back wall to the door (over ~11 feet), but not smoothly. It was also lower in the middle than on the left or right. We used Level Quick, mixed it relatively thickly and trowled it in to give a smooth - but not level (that would have required filling the whole 1,000 ft3 apartment with 1 ½ inches of compound) - surface. It buckled in the middle - the thickest portion - within a few days and before we could get tile down. We found out we had not used a primer as we should have, and the compound had not stuck to the existing cement in that spot. I tore up all the underlayment that had not stuck and refilled that part. It appeared to stick this time and, after waiting 5 or so days to make sure it wasn't moving, we laid our tile. 3 weeks later the tile starts cracking. To make a long story a little shorter, the thickest part of the underlayment again had not stuck to the existing concrete in spite of the primer. The rest of our renovation is done, but our kitchen floor is a disaster!! What can we do?!? I am afraid that retrying the Level Quick compound with primer won't work unless I can figure out why it failed to stick in the first place.