N. Thornton wrote:
"JK" wrote in message
...

Indeed the concrete outside is at a slightly higher level than the
floor
inside,

problem located. The solution to the problem is to solve the problem.
Ie lower the concrete level outside. Since that will give you a lower
water collecting area you will also need to add a drain to prevent
water collection.


You're right, but it's not an option. I need some kind of remedial
treatment for a problem created by bad design. Breaking up 10 sq metres of
concrete, digging out, installing drains is just too much, partly from a
cost point of view and partly because any mess has to be carted through the
flat to get it away.