Grimly Curmudgeon wrote:
We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember The Natural Philosopher
saying something like:

But beware of massive screeds on a suspended wooden structure. I would
rather go for a very stiff wood structure, with kingspan under the floor
and pipes just laid on top of that, and ply over. Then tile the ply.
Make that floor a lot stiffer than you would for carpet or
laminate..maybe 7" deep with herringbone braces..then there is plenty of
room for insulation and pipes as well.

The above would work ok, but with the addition of heat spreader ally
plates would work better.

Kingspan has ally foil on it. Its a moot point as to whether the cost of
adding more is worth the benefit. At this point I have no opinion.