Damp floor, issue or not?

[JackReacher]

Took up the carpet and inset coir doormat in the hallway (we are having Karndean fitted) and discovered a large damp patch under the doormat. Initially I thought moisture was just getting there from people coming in with wet shoes, but I don't think there would be much as haven't had a lot of rain recently. I'm wondering whether there is a bigger issue, as the damp proof membrane is slightly visable along with some very damp bits of crumbling scread. It's dried off a bit since the mat was first removed, but there are still damp patches, and especially by the skiting. What do people think?

[Lotobear]

Your floor layer will sort it, probably by laying a surface DPM. Take their advice on it.