slate tiles + concrete patio

[DrayTek]

Hi there, in need of a bit of advise. I've recently tiled a bathroom for a builder, happy with my work hes asked me to tile his patio with slate. I've neither used slate before nor tiled outside so a few questions
1/ Do i need to seal the concrete ( concrete is clean and appears to be fully cured )
2/ I intend to use sand/cement ( mainly in order to minimise my costs if i under estimate ). What mix should i use ? 3:1 ?
3/ Do i need to use an additive in the mortar ? i.e to provide frost protection.
4/ Do i use a solid bed ? if so how thick should i be laying the mortar?
5/ Theres an expansion joint in the concrete , do i lay an expansion joint on top of this one for the tiling ?
6/ Is the slate sealed before or after laying for grouting ? and if after will any mortar i get on the slate wash off ok as i go ?
Many thanks
Ed.

 

[White Room]

I've done slabs so can go on that, I would slurry the concrete with sbr and cement.

I used a mix which was 2 25kg sharp sand (screeding stuff), 1 25kg soft sand and half a bag of cement and some mortor plasticiser.

Follow the control joint thru to the slate