On Mon, 22 Sep 2008 10:51:45 -0700 (PDT), Adam wrote:

Sure, but there'll still be a gap, unless I'm missing something
obvious. See my piccy:
http://www.snowstone.org.uk/temp/plan.png

Overlap the two bits of DPC. One bit under each joist for the entire
length that they are (or would be...) in contact with the concrete
support.

Later, Phil P wrote:
Personally, I wouldn't use anything underneath timbers in a situation
like this - it merely holds any water in place, right where you don't
want it -

This seems like a good point. There will be rainwater above the DPC
and damp below the DPC, so what's the point in it? Why not just lay
the joists directly on the concrete?

Any rain water will soon evaporate and dry in the well ventilated void.
The damp from the ground will rise up due to capillary action and be there
all the time...

--
Cheers
Dave.