Down rating cable chased in aerated blocks

[hmmm]

6mm cable for oven and hob is plastered into the internal wall made of aerated concrete blocks of a cavity wall. As these have some thermal insulating properties (between 1/2 and 1/5th as insulating as rockwool by the looks of different specifications) how should the cable be down rated?
Background is that I am deciding what is the maximum wattage of oven I can install on the same circuit as a 6000W induction hob as I would like to purchase a new oven.
Total length of cable from Consumer unit is 5m (laid in air over rockwool in the attic) plus 1.5m to the Cooker Switch 45A DP (chased in the aerated blocks and skimmed over with plaster then tiled) plus 1m in the wall again to the cooker outlet plate. 32A MCB at consumer unit.

Would it be sensible to treat the cable as if it were Reference method 100 or 102 ( see http://wiki.diyfaq.org.uk/index.php?title=Cables ) given that the blocks are 100mm thick ?
Also the cavity is soon to be filled with polybead insulation. Does this further down rate the cable?
Thanks
Mark

 

[Taylortwocities]

The cable is chased in the face of the blocks, not in the cavity? Is that right?
The cable cannot be in the cavity for lots of reasons. Contact with poly beads may degrade the plasticiser in PVC cables and they can/will fail over time.

If only chased on the face side then no downrating is necessary. Otherwise you have a problem, Houston...



You can probably get away with a small single oven (<3KW) as well as the induction hob. Otherwise you'd be better off with a separate feed for the oven.

 

[hmmm]

Yes it is chased in the face of the blocks and not in the cavity.
Good news as lots of simpler single ovens <3kw. If it were larger I would take the opportunity to get a new feed and place the oven elsewhere in the kitchen.
I have seen various threads about applying diversity to hob and ovens, and one saying that induction hobs behave differently to older electric hobs and advise against this. What think you?
Thanks
Mark