If it's little spots where the paint looks like it's 'gone crackly' - that's bird shit you didn't wash off. I know, as my roof is covered in them. Fortunately t

If it's little spots where the paint looks like it's 'gone crackly' - that's bird shit you didn't wash off. I know, as my roof is covered in them. Fortunately the undercoat seems impervious - so can be considered as 'just cosmetic' (although entirely likely you have another affliction).