rendered wall moisture / mould on one wall

[cansu]

Our house is rendered. The side wall is starting to have some issues with mould patches upstairs. My dd's badroom has had mould on one wall and I have now noticed that there is what looks like moisture has dripped from the top of the wall on the stairs - the wall seems dry but there is some mould in patches and whilst it is very high it looks like something has dripped at some point staining the wall. Is this likely to be a problem with the render?

It could be the roof, the guttering, the render, flashing where roofs join, or just no ventilation. I would get a surveyor to do you a report and then get a builder to put it right. Is the render cracked so rain can drive through?

I don't know because it is right up against my neighbour's boundary. You are right - I am going to get someone round to have a proper look though.

Please post some phots, with something in to show scale.

Are there brown stains? Or black mould?

Do you drape wet washing inside the house?

Hard to take decent photos. No wet washing. Do have however downstairs bathroom with no ventilation which we are saving to put right. Brownish stain on highest part of stairs wall. Black speckly mould patches lower down. Same speckly patches on dd wall. I ended up trying to scrape off paint as I want to redecorate. Am concerned though that no point until I sort out cause.

piglet on the subject of damp/condensation (sorry for highjack op) is there some sort of dehumidifier that can be built into a house (like you would an aircon unit) ? I'm sure a house I worked in had one but I can't see anything online and wonder if I have dreamt it.

British houses shouldn’t need dehumidifying if they are constructed properly and ventilated. After last summer, air con seems attractive though!

Brown stain at the top is probably a roof leak. I doubt it is render. If there is a gutter or chimney on the other side it might be that. If you can get into the loft with a torch, do.

Ask around for personal recommendations of a well-established local roofer.

Advertising websites are not a good source.