"Greening" of natural slates

[lfcjfc]

We fitted Cupa H3 natural slate on our new build about 18 months ago. This is their second Winter and recently I have noticed that the slates on the North elevations of the house are taking on a green hew. Is this normal? Has anybody else seen this with Cupa slates? I'm not to bothered at the moment but would be interested to know how green they will get.

 

[Smashbox]

Is it moss/algae? If so, you could try power hosing it or treating it with a product like Mossgo.

 

[Eddye]

There is a copper strip which can be installed on the ridge tile which stops moss from growing. I learned it in construction studies in school. where did you get the slates?

 

[briancbyrne]

have seen a lot of estates with this type of slate (particuarly in the North) and the slates have seen them get progressively worse over time. I personally think they really make a house look very unsightly.