What's causing this wetness?

[Norpeth]

We've just bought a house which has been empty for at least a year and needs a lot of work. After pulling the carpets up, there was a huge wet patch on the floor boards and the area circled on the wall is soaking too. The radiator/pipework isn't leaking. Any ideas please? Can't see anything obvious from outside. It's an upstairs room. Thanks!

Is rain driving in from outside and going down the wall? Does the window fit properly? Is water coming in under the window? Is there any damage to brickwork or rendering outside? Is any water discharging from a pipe or guttering outside at that point? Is it a cavity wall?

Thanks for the reply. There's no damage to the brickwork or anything obvious from outside. We did discover today that all the airbricks have silicon in them which we will fix. It is a cavity wall.

Have you checked the loft incase there's a leak in the roof that's coming down onto the walls settling on the floor?

Water either comes in horizontally or comes down into a room. Stand outside with a hose on the window and that bit of wall. See what happens. Was there a leak from water storage above and it’s not dried out? Clutching at straws but this water cannot just have appeared out of thin air. Was the carpet damp that you removed?

It could be condensation but it seems unlikely if it’s in the floor.