On Sun, 10 Aug 2003 00:59:51 +0100, Martin Angove
wrote:

He has suggested that the concrete floor should be
replaced, simply because "they didn't use a damp proof membrane in those
days - though it looks fine at the moment".

Damp proof membranes have been used since the Victorians (slate, blue
brick, bitumen). They weren't stupid, even if they didn't have
convenient rolls of plastic stuff to use.

If it looks dry, then leave it alone. If it's dry, then chances are
there's a layer of bitumen poured underneath there somewhere.