Mould in corner of bedroom

[diytrader44]

Wondering if anyone can advise...as pictured there is a big damp spot in the corner of my bedroom. I've had the guttering checked and that's not an issue so wondering if there could be a loose tile on my roof. Any ideas are much appreciated!

Do you notice damp in the attic space above? Any chance it's condensation?

I get a dampish wall but no mould. It may be condensation because the dehumidifier gets rid of it for a few days. however, I don't know what that is costing to run annually so I am hoping to get to the bottom of it. I saw PIV recommended on here but it would use attic space.

Could be an issue with the pointing in that corner.
We had a similar patch but the guttering was new & the roofer went up and had a look and said it was the brick pointing.

Paint a waterproofing solution onto exterior brick, Thompson’s waterproof seal from Wickes about £20. Water seeping into bricks then freezing expands and causes small gaps.

Could also be condensation, so try a dehumidifier as suggested. Also try a mould resistant paint additive (mould paint is expensive and colours limited) to add to usual paint, after using Zinsser damp seal primer.

Do you dry laundry inside? If so get a dehumidifier this looks like condensation mould to me