We're missing a trick with the insulation, that's for sure.

Yes, but it also gives perimeter insulation, which is a better place for it than under the floor [IMO]

Concrete itself is virtually damp proof especially above ground.

US/Canadian construction uses something called a "sill gasket" between the top of the concrete foundation and the wood sill plate that the framing is attached to. This is to prevent damp entering the wood and rotting it. However, in many places in the US and Canada, basements are the norm and so the wooden structure is usually a fair way above ground level anyway - in a basement that's 8 feet deep, probably only 6 feet or less is below grade.

All that said, the 110 year old house I live in in Montreal has no dpc/dpm of any kind. The floor of the basement is about 4 feet below grade and is concrete directly on the ground; it is dry with no signs of any kind of damp. The walls are 36" thick limestone going to about 2 feet above grade and then the solid brick walls (no cavity) sit directly on top of this with the floor joists resting on the thick foundation wall. There don't appear to be any problems with damp - though the basement is heated. Perhaps this is the trick that makes a DPC/DPM unnecessary. The footings of the building use "French" drains. The frost level is about 42" below grade (maximum) and so pipes and the like are usually at 48" below grade.

The new house we built used a concrete foundation about 6 feet below grade at the deepest point. As there was a lot of water found during excavation on one side of the property this side was coated with a bitumen spray. The concrete basement floor has neither insulation nor DPC/DPM and is dry as a bone and not cold either (going back to the debate about underfloor insulation).

It was certainly a revelation moving from damp obsessed UK construction (an old cottage I had in Glossop supposedly had damp problems and we were told required a chemical DPC as a holdback clause on the mortgage - after three quotes we decided not to bother as one implied water was flowing in at a rate equivalent to Niagara falls and one said really there was no problem) to a place where it is never even mentioned and cavity wall construction is pretty much unheard of. My late father was in the concrete business and it was my understanding that pretty much any conventional mix made with Portland cement is essentially waterproof. We always enjoyed looking at the defunct concrete-hulled barge lying abandoned in the mud in the RIver Humber :)

Paul in Montreal.

They don't have a DPC in France either - they have a vide sanitaire or crawl space whistling underneath. Looking at our engineering drawings, we have 85 cm concrete pillars on top of 60 cm of ballast, then a 20 cm concrete slab with 25 cm of insulation on top. In the cave / cellar, there is waterproofing - but I'm not entirely sure what. There doesn't appear to be any insulation round the concrete pillars (60 cm are above ground level).

Couple of disconnected points:- Many houses in the USA actually have sump pumps, that is the basements leak water which is pumped out and a dry room built within the basement area.
My barn in Wensleydale typically has the water table about 8" below the flagstone level, and a mate of mine in the New Forest has a well in his garden, last weekend the water level in it was within 10" of the grass surrounding it! No sign of damp in his 1920s house whose ground floor is less then 18" higher then the lawn.
Frank

Posted By: chuckeyMany houses in the USA actually have sump pumps, that is the basements leak water which is pumped out and a dry room built within the basement area.

I can attest to that fact in Canada too. Most new houses in Montreal are built with basements and many of those require sump pumps. My 110 year old house has one as the water table is literally inches below the basement flow - yet we don't have a DPC and have no problems with rising damp, though the stone basement walls are sometimes damp to the touch, depending how much rain there's been or how much snow has melted.

I remember when I lived in Glossop I was somewhat obsessed with rising damp, having been given dire warnings by the inspector when we bought an old house. Various chemical DPC companies also painted grim pictures with visions of water pouring through the walls and tanking up to head height etc. Finally one of them said it didn't seem so bad and recommended not to do anything. Which is what we did. Never had a problem. I suspect most of the damp was condensation in cold dark corners, rather than true rising damp.

Paul in Montreal.