Mould/Damp on ceiling Query

CatFromHue

We had an extension put on in 2017/18 that extended the bedrooms out, roughly drawn below. This involved adding an air vent to the back wall as well. Over the last year or two I've been noticing mould starting to build up near the vent and a few spots of discolouration on the inside of the extension where the wall and ceiling meet. I'm worried that this might be more than just a bit of mould, the room is very warm naturally, and there might be a bit of a leak. There's a few cobwebs in the first pic but you can see the mould around the vent. Does that look like a bit of a leak?

ted1

probably just a cold soy on the wall. I assume you clean the mould off when it’s appears.

You could look at a electric/ mechanical vent with a built in humidistat

10-10-20

Probably the block used for the closing the cavity at the top of both leafs. Even pumped cavity insulation suffers for the thermal bridge at that point.

Monitor and Manage the RH and open windows when you can.

CatFromHue

Thanks for your comments. Below is a few close up pics of the affected area. It's the middle one that had me thinking is it more than just some mould.

whizbang

Thats a water stain in last 2 pictures.

Have a look up above in Attic.. Is this a flat roof ?