Damp patches on inside of gable (?) wall

Ben1989

Hi all. 

Had artex stripped off the ceiling and walls of the hall, stairs and landing. We then had them skimmed.

I’ve come to paint and noticed these damp patches on the wall. The paint has been on there for three weeks so I know it’s dry.

It’s obvious it’s damp but I cannot see any where the damp would be coming in and thus no idea about how to prevent it.

The outside wall is rendered and painted albeit old.

What’s the best way of diagnosing and remedying the problem?

I haven’t painted the rest of the stairs but I anticipate the same problem on it.

twopenny

It looks a lot like the plaster is drying out still. Either from the heating or delay due to the damp weather.

The surround at the door is a different colour to the plaster. Has it been painted? Or skimmed?

Ben1989

The plaster was on for 10 weeks prior to painting so I don't believe it's plaster. Using the window as an example, the other corner of the window is bone dry. 

Regarding the door I think that's a bad image. I'll upload a clearer one of the area.

koalakoala

Plaster takes a long time to dry if there is no heating on. I assume there was ?

Ben1989

koalakoala said:

Plaster takes a long time to dry if there is no heating on. I assume there was ?

Yes. It's really not the plaster as the patches reduce and get bigger slightly. I've a huge double radiator in front of it

Ben1989

Here are better outside images.

stuart45

If that's a solid 9 inch wall, any cracks in the render could allow moisture in.

Bendy_House

As you suspect, Ben, the patches look to be too intense, too localised, too defined to be anything other than 'external'. The damp on the window reveal is especially striking!
The next time it rains, see if the gutter is overflowing and could be sending water down the top of the wall, behind the render.
There is a small crack in the render further down, but hard to imagine it's JUST that.

Ben1989

There a small crack coming from the bottom corner of the window. I'm not sure if that's the source of all our problems. It would explain the window as everything around the window frame is sealed (inside and outside).

stuart45

If that gable wall takes a fair bit of driving rain, you'd be surprised how much water can get into a horizontal crack. When hacking off old sand/cement render you often find water trapped behind the hollow bits.
Think how much water can get through a small gap at the base of a shower.

Bendy_House

Yes, I see that crack.

I guess any water getting through there could be making it's way to that vent where it'll have a path to the core of the wall, and likely to the lintel above the bottom window - which is where some of it is coming in.

Are you up for investigating - putting a ladder up and seeing where that crack starts at the cill of the upper window - any gaps there? Does the render sound solid or hollow?