Strange mark appeared

[cjmort]

Hi there In the last few days this has appeared on the corner of an internal wall downstairs. It’s progressively got bigger. Ceiling is dry and no pipes are leaking upstairs (also no pipes in that wall)

The other side of this wall is the hallway and the back of this wall goes up the stairs.

 

[JohnD]

Not strange at all.

Water leak above

Please photograph the room above, and the wall outside and on the other side.

 

[cjmort]

But why isn’t the ceiling wet? I’ve recently had the floorboards up and checked it

 

[cjmort]

Above there is the landing

 

[JohnD]

You haven't found it yet.

Post more photos please. It would be especially interesting to see under the floor above.

Is that a knock-through wall, done after the house was built

 

[cjmort]

Yes that pillar holds a lintel. On the landing the only pipe running through the floor on the landing is the gas

 

[cjmort]

It’s completely dry under there and I’m directly above that mark upstairs

 

[JohnD]

It might be running along the lintel from a leak.

 

[cjmort]

Will check more floor area but the lintel is quite a distance from that mark and nothing above it is wet. I may be wrong but I would have thought it would show on the plasterboard ceilings near the lintel? That corner is quite a distance from the lintel, and low down

 

[JohnD]

If you don't want to post more photos, you could chip off the plaster in that wet corner and follow the water back to its source above

 

[cjmort]

Will do more investigation and send some pictures! Thanks