levelling 30-60mm, plastic membrane?

[ubeaut]

Hi guys, Im about to level my concrete slab verandah and box it in to form part of the kitchen. I will be laying slate over the top to finish. From 30mm near the house out to 60mm is what i am levelling to bring up to house floor level. Do i need to lay plastic in between the existing slab and the leveling coat? If i do it wont bond etc, but i Will be dynabolting the bottom plate of my wall frame and could just use longer dynabolts to go all the way into the original slab thus securing...

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