Can I tile directly onto chipboard?

We have just had a sunroom built and want to put a (400x600 calibrated) slate floor in. The builders were aware of this and have put a chipboard floor in; they say we can put the slate straight onto this as long as we use flexible adhesive. Some of the forums seem to say we would need backerboard on first. What do you recommend? The total area is 3300x4500mm2.

We do not recommend tiling directly onto a chipboard floor as this will become structurally unsound should the floor be subject to water ingress at any time. It is therefore considered best practice to overboard the chipboard with WBP plywood (as this is water resistant) and apply 2 neat coats of the Granfix acrylic bonding and priming agent before tiling commences.

It is essential you use an S2 type adhesive (ultra flexible) for tiling onto a wooden surface, we would recommend the Granfix Ultimate flex which is a highly polymer modified adhesive.