A lot of this stuff is relatively new to the building industry, thus they’re pioneers, often having to work out how to bolt it all together as they build it. Bruno and I have the same book Planting Green Roofs and Living Walls / Toits et murs végétaux but, in either language, whilst being long on general principles and lovely photos it is frustratingly (and litigation-avoidingly ?) short of accurate construction detail.
From the inside out, their roof has Fermacell boards nailed onto joists deep enough to slot in a straw-bale as insulation, with a breathable sarking board, then an air gap to allow moisture that escapes this breathing roof to exit below the waterproof layer. On top of wooden spacers are nailed sheets of OSB/Stirling board, which provides a structural surface over which is laid a geotextile then the EPDM “pond liner” membrane, then substrate and finally, beautiful, drought-resistant sedum plants.
No sooner had Bruno fixed the Stirling board with a “why-use-only-one-nail-when-it’s-this-easy” nail gun, than a chap who’s built straw houses and green roofs took a look at it, sucked through his teeth and pronounced the air gap insufficient. Bruno had decided to saw through the well-fixed boards, to add some more wooden spacers and refit 950 €uros’ worth of new board. I’m a man that easily panics when faced with this sort of crisis, unless the crisis belongs to somebody else. I can then become usefully calm and supportive. I also think that I project my fears onto such a situation (i.e., imagining how it would be if I woke up to discover that it was actually my problem) which is further incentive to get involved. Don’t worry, I said, between us, and using my British-made nail puller, we can remove the boards, add the spacer and nail them back on again. It took a fair amount of time and a lot of effort but that is what we did. Wouldn’t you think, after such a victory, that they deserved a break?
After an unfeasibly dry summer, autumn weather rained off the first two attempts to fix a date. Having left the tarp off for a day to allow the boards to dry, a heavy dew left them worryingly damp. But then the expert help (Jerome, the supplier of the materials) was late to arrive and it was very blowy, neither good for the nerves but nevertheless helping to dry the roof.
When we rolled the membrane out to cut it to size, we realised that Jerome had only ordered half the EPDM we needed … oops. Then there was an issue with the height of the flue pipe from their woodstove, with more delays, measuring, negotiation and worrying, during which, I drove Jerome to the tractor dealers who were going to rent us a fork-lift to lift the heavy roll of membrane onto the roof.
After finishing a very long phone conversation, Mr Hervé apologised that he had had to lend it out to a farmer whose own had broken down and was sorry that he hadn’t informed Bruno as he didn’t have his phone number. As we returned, the stove guy was leaving. That was before we’d discovered that the junction between two pipes meant that the collar didn’t fit and the stove guy had to be called up again, reluctantly agreeing to reappear after lunch. It was fast becoming one of those days when you want to return to bed, roll up into the foetal position, pull the covers over your head and hope it all goes away.
Perhaps I exaggerate. The day finished late with one (of two) roofs watertight—a significant step forward—but leaving Bruno physically and emotionally exhausted. Where do we find our hero at the end of such a testing day? Howling at the moon? kicking empty boxes around the worksite in frustration? drowning his sorrows with cold bottles of Stella Artois? None of these: I returned having popped home to do the evening rounds of our animals to find him reading a bedtime story to Liam and Jeanne. I think some sort of medal is in order!