Looking for some advice please. Our 1930s house was re-slated 9 years ago. The contractor (allegedly) used Siga 38 slates with a workmanship/materials guarantee of 30 years. We are about to embark on on a loft conversion and the scaffolding went up this week. When I popped up to take a look at the condition of the chimney I was pretty concerned to find that a lot of the roof slates are quite rusty and in some areas the tiles appear quite affected. I have attached a few photos.
Should I be concerned about this? or is the rust just cosmetic?
