Help!: What's a flexible additive?

[Toritwix]

I am about to embark on my second travertine grouting job for a shower cubicle. The last grout I used didn't specify the need for a 'flexible additive' but the new one does (on a 50:50 with water basis). What is a 'flexible additive'? Can I use PVA?
Hope someone can help.

[Dave]

Why not just buy a flexible grout..?

[doug boardley]

if you have PVA, throw it in the bin!!, flexi additive is a latex liquid that transforms grout from rigid to be able to withstand a certain amount of substrate movement.The most popular is probably Bal GT1

[david campbell]

without being cheeky,i'm not sure you are sure of what you are doing for such an expensive tile,i think you are better calling in a pro

good luck if you decide to go it on your own

[whitebeam]

Can you get hold mapei ultra grout in your area, tile giant or screwfix