Damp diagnosis, help much appreciated

[pmj1980]

A few days ago I noticed damp patches above the skirting board in my hallway. These damp patches then went away, but have come back a couple of days later. I can't see any staining, and I would be surprised if this had been going on for long without being noticed - it's in an area of hallway near our kitchen and back door, so we're in there quite often.

The house is a late Victorian terrace. I bought it at the end of last year so I don't know whether there have been any problems long-term, although the house has no other damp issues that I know of.

In the photos you can see that the two worst areas are near a stopcock and a radiator. Neither appears to be leaking (although that stopcock was replaced a few months ago after it started dripping).

Any ideas? There is a step in the hallway (visible next to the radiator) so this is the lowest part of it. There is no damp anywhere else. They are not external walls, apart from the fact that the wall ends adjacent to the back door.

I would worry that it's rising damp, but it seems to have come on suddenly and it comes and goes. Any suggestions would be very much appreciated.

Edited to add: all my pictures are upside down! I have no idea why, because they're the right way up on my computer. Hopefully you get the idea.

[dewaltdisney]

Do the pipes go into floorboards or is it solid? It would be a good idea to check the pipework as this does really look like a pipe leak to me.

DWD

[moderator7]

I've rotated the images for you.

[wes56]

feel the carpet for damp or pull it backoff the grippers and look for damp. go under an look if its a suspended floor.
whats on the other side of the wall?
probethe skiting with a compass point see if its soft

[pmj1980]

Thanks for the replies (and the picture rotation).

I've pulled back some of the carpet and the grippers etc. seem dry. The skirting boards seem fine too.

It's a suspended floor. Pipes go down beneath the boards. The damp bits are on two walls that join at a corner, and on the other side of these walls is the dining room. There is no sign of a problem in the dining room. However, the step in the hallway might be relevant. The step is halfway along the hall, and the damp patches start at the step by the radiator (shown in the third pic). All the damp patches are in the lower section of the hall, along from the step and round the corner. There are no damp patches at all in the higher portion of the hall. The dining room is at the level of the higher part, so in some ways it isn't surprising that the problem isn't showing up there.

Maybe a pipe is leaking in the space below the wall, and the plasterboard is getting wet (and soaking it upwards)?

[wes56]

get under the floor if you cann an have a look.you say plasterboard, is the wall dot and dabbd? you can soon see if the ch system is leakingby checking refills topping up.