URGENT esterior tile question

I am having a contractor pour a concrete slab for a walkway on one side of my house. There is a concrete block retaining wall along the back and one side of the walkway. This area has a lot of moisture.

I have a few questions:

1. What needs to go between the slab and the tiles

2. What waterproofing materials are best to use in this instance

3. What is a good way to slope the surface for water runoff

4. How much room should he leave for the tile and underlay, waterproofing etc.

Thanks in advance for your time and advice!

 

1)thinset. Climate will decide which one to use, just bagged modifed or unmodifed/additive
2)what is the reason for the waterproofing? Tile, thinset and the slab won't care about water
3)slope the slab when its' poured He's a contractor. He should know and do this without you posting on a message board.
4)He should know this too, he's a contractor, right? How thick is the tile, what size tile, why do you need to waterproof between the slab and the tile? It's an outside walkway. If you are setting the tile, what climate, why the waterproofing?
IF you know the size of the grout line and tile, have him strike control joints per the tile spacing so you don't have to cut a tile to create an expansion gap over the control joint. Don't want to bridge them with tile. Wait 28 days before setting the tile.

 

I would agree with the prior post, but if you are waterproofing the slab to keep water from wicking up from the ground you need some sort of membrane underneath the tile otherwise the tiles might start popping-up on you. The two that I have used with success are Custom Building Products' RedGard and CompoSeal Gold. The RedGard is a roll-on/trowel on "goo" that dries to a thick membrane while the CompoSeal is a physical mesh material.

Several of the major companies make similar products, these are just the ones I'm familiar with. I would definitely have your contractor determine if the waterproofing is needed and if so contact the company to make sure that their product works in your specific situation. Properly installed most companies will back their product, but if you don't follow their instructions to the letter they will often invalidate any warranties.

Good luck.

-Matt