Andy,
Invariably the majority of our houses are of timber-framed construction, with a Brick Veneer layer over the outside.
And the use of a timber floor has been thrown out, in favour of Concrete slabs, where everybody wants Underfloor heating elements installed before the concrete is poured over the top.
Just a note about these systems, you'd be suprised how many houses here had these U/F heating systems installed when the house was built, but the elements have been blown up by voltage surges, caused by nearby Lightning strikes on overhead lines.
After that happens, that's it, you can't use the system again.
And with the majority of the Wire-pullers, we call Sparkies here, not knowing what a Surge Diverter is, or even how to install one, this just makes the situation worse, as the Manufacturer of the most commonly installed system here stipulates S/D equipment to protect the U/F elements, most Sparkies just thumb thier noses at that idea. [Linked Image]