Is anyone familiar with a technique for laying porcelain tile directly on uncured sand coat. I ripped put a brick hearth and want to lay 14" porcelain tiles in it's place. I worked briefly for a tile contractor in the mid 70's and he used this technique. He would lay down a 1" sand coat bed of sand, portland cement, and just enough water to give it a "sandcastle" texture. It was usually over metal screen on plywood. He would then screed it level, dust with portland cement, spritz with water, and lay the tiles. I'm just not sure of the proportions to use. The tile shop where I bought the tiles never heard of this and suggested I go thinner with the Quikrete sandtopping mix, let it cure, then use thinset. I had to grind/cold chisel the existing concrete slab because there is a 3/4" height difference from one side to the other (that was fun)and I need the height consistent to meet the hardwood that will surround on 3 sides. The tilebed will extend beyond the slab all around onto the aspenite sub floor. I prepped the entire surface with E Z Flow Primer 100 to facilitate bonding, then nailed matal screen to the aspenite portion. Anyone know if the Quikrete can be used in a drier than recommended mix to do this? If it is strictly a sand/portland mix, it should work if I can replicate the proper moistness by feel. I'm doing a fairly intricate bordered diamond pattern which I dry fit on a sheet of plywood, so I just have to fix the screeding rails and go. I'm just afraid to botch it by using the wrong sand mix. Sorry to be so long winded, but any advice would be appreciated. Thanks.

Hi Rick
I'm much more comfortable letting the mortar bed cure first. I tried it a couple times and it seemed to take me more time. But that's just because I wasn't used to it.
Mix the sand-mix as you would for regular mortar beds (deck-mud) as you described as sand castle texture. I back butter the tiles first and then beat them into the bed. But I have only tried it a couple of times and would much rather work on a cured mortar bed.
If the bed is packed too hard, it's difficult to beat the tiles into the bed (even a little), so try leaving enough play in the bed to allow you to set the tiles level.
Maybe someone can be more helpful than I am with this process.

Harry, thanks for your input. I'm not sure we're talking about the same consistency though. You mentioned back buttering, but our mix was so dry that we mixed it at the curb and carried it inside in the paper bag. Pretty sure it was mainly sand, a few handfuls of portland, and just enough water to make it mouldable in your hand. The Quikrete (sand topping mix)bag says to use 3.3 liters per 60kg bag which would make it much soupier. I may let it cure, then use thinset afterall. The curing time on their website says minimum 5 days, but this looks to be for outdoor concrete patching applications. Any idea how soon it would be safe to apply thinset in my case?

Yep ... same stuff I'm talking about. After it's packed and scraped you should be able to walk on it without serious indentation from your boots. It's the only way to mix deck-mud .... a dry consistency as you've described.
The directions on the bag don't apply to the construction of mortar beds.

Installing ceramic tile over a mortar bed doesn't stop curing .... as long as moisture is in the material it continues to cure. You can install tile the next day with thinset.