DPC for ceramic tiles?

[tryer]

I have a porch about 2metre square, with old but very firmly fixed marley type vinyl floor tiles (foot square, thin). Based on other parts of the house I expect a black bitumen type painted goo underneath.

I intend to lay ceramic floor tiles straight over the top.

Q - Do I need to lay anything over the top for damp proofing? (I currently see no evidence of damp coming up)
Q - I would prefer to use a pre mixed adhesive/grout - the only ones I see are for wood or concrete bases - should I go for the concrete base one?

thanks for any help

 

[warehouseman]

The proper way, if you retain the marley tiles, is to coat them with an acrylic PVA (covers the damp scenario if it does exist) and lay tiles with a Flexible floor adhesive. Powdered cement based is always better but i suppose if you prefer a ready made tub of 'flex 'adhesive & prepared to pay more for a potentionally lower quality material, so be it. Remember, ready made stuff is invariably slow setting 24/48 hours opposed to approx 3/4 hours for powdered. Finally, many might use a standard adhesive without the flex & of these 75% will be ok. The remaining 25% might have tiles popping up in future.