Advice please! Damp brown spots on wall

[housebay123]

We recently purchased a very old, grade 2 listed property. As with most properties of this age, there isn’t much insulation and we do sometimes have issues with damp and mould, but most often it has been curable. There is one wall in particular however which is in our third floor hallway, that has brown/beige (almost oily) spots that are seeping through. The spots itself feel cold and damp, and sometimes slightly wet. On the other side of this wall is the front exterior - it does get a lot of rain, but it doesn’t seem to be happening in any other part of the house, and we have recently completely stripped and repainted the entire exterior. We have tried multiple stain blocks etc from the inside to treat this wall but it eventually just seeps through again. The bathroom is opposite and so we initially thought it could be something to do with the steam and poor ventilation but it feels odd that it’s only happening on this one wall. Does anyone have any idea as to what is causing this particular type of spotting?

 

[JohnD]

These brown spots - they're not on a chimneybreast?

It does sound like rain penetration. Please post photos of the entire wall, on the outside, all the way up to the roof and gutters. Include all nearby downpipes, drains, bay windows, sills, bathroom and water tank overflows, extractor fan vents, boilers, if present.

On the inside, photograph the entire wall, ceiling to floor, corner to corner, including the ceiling above.

You mention a bathroom. Does it have pipes going into or through the wall? Is a bath or shower above or near the damp? How, and when, is the bathroom ventilated?

You don't drape wet washing inside, do you?