Damp patch in concrete floor

latedeveloper

My daughter has a young child and doesn't have time to ask this herself.

A small wet patch (about 10cm sq) has appeared in the hall carpet next to where it meets the stuck-down plastic tiles in the kitchen. It isn't next to a wall. It came around end of last year, then it dried out, now it is back.

As far as they can see, the water pipes go up and run through between the groundfloor ceiling and the first floor - not through the concrete. If pipes were the problem their insurance company would cover consequential damage but not the plumber to fix the pipes - if the problem is ground water welling up then they say they are not covered.

The house has concrete floors and is pretty much on a level with the ground outside. When they bought it a few years ago their surveyor found one of the chimney breasts was slightly damp, but no other problems. He recommended some work on the roof which has been done. The dpc had already been replaced. He said there was a possibility that if they had problems they might need a french drain round the house. But there have been no problems till now, and this patch is not near an external wall.

In this extremely wet weather damp has also appeared beneath the first floor back bedroom window but we are assuming this is a separate problem with the window, the frame, or the pointing.

We are a bit unsure how to investigate the damp patch on the floor, or who to call on - any local builder (they don't know one yet), a damp specialist, a concrete specialist?