The ceiling on the portico in front of our house was replaced a few years ago. When it was replaced the new ceiling looked terrific and we were delighted with the result. Move on a couple of years and a few heavy rainstorms over time and the ceiling was beginning to look a bit suspect.
I thought the stain looked similar to mould so decided to give it a go with some bathroom mould remover spray. I got out the ladder and set to work. Sure enough after leaving the spray on for ten minutes I then wiped it off and the ceiling was back as good as new.
Well worth the effort. It will be interesting to see what happens in the next heavy rainstorm.That is sun reflection in the centre of the ceiling.