Pam Hatfield wrote:Does anyone know how they USED to build green roofs? People keep sending me photos of old huts in Iceland and other places, some now heritage sites and there they are standing cheek by jowl with shingled buildings and everything's still looking sound. For sure THEY were built before EDPM pond liner or any other sorts of plastic. I have some pretty good idea but would love to hear from someone who knows for sure how it was done.
I just registered to answer your question
I've written a bachelor report on green roofs as it's an interest of mine as I come from a country which has a lot of turf roofs and because I grew up in a house with a traditional turf roof. Here is an example how modern traditional turf roofs are made in Faroe Islands, as well as some comparisons at the end with how it was done before the advent of plastic http://www.kontrast.fo/tidindi/pdf/18.pdf
Today birch bark is only added at the footing of the roof if it's an old building, to preserve the old look. But most modern houses don't have birch bark at all due to cost. But it's said that each layer of birch bark has a lifetime of approximately 10 years, which is only added for each layer... e.g. 5 layers of birch bark and you can expect 50 years of light repairs and maintenance.
NB! The cost of birch bark paved the way for the dimpled plastic method with a fishing/trawler net underneath the turf and sometimes on top of the turf to ensure it stays put (it's very windy in the Faroe Islands)
And the climate has to be able to support the rather water-demanding turf roof, otherwise it's going to be a costly affair to water. For that case a modern green roof with carefully chosen sedum plants would be more suitable for locations where there are more dry periods.