We’ve been noticing that the way we learned to do roofs back in the noughties, and the current national guidelines for how deep the growing medium should be, are being overtaken a bit by our changing climate. We’re finding that the wet and mild Winters we’ve had, followed 3 out of the last 4 years by long dry Springs, is causing significant problems even for established roofs.
We’re learning on the job, but we’re paying close attention and have been implementing ideas for how to address this. The tell for us was when we visited the roofs we care for for one of the Boroughs in West London: all meadow, some installed to current GRO guidelines, one in particular by John Little on a small refuse store outbuilding that we inherited that went way beyond. The depth there was 250mm or so at its deepest. And at the end of the long dry period as we came out of the first lockdown in 2020 it looked like this:
Ever since we’ve been – in ad hoc and now more systematic way – encouraging clients that this is the way to go. We’ve experimented with what we call HayBase and that def has its place, especially where the build-up needs to be super light. But we like the multiple benefits of going deeper. Here’s why:
- best of both worlds: deeper for drought resistance, but also roots clear of wettest zone with generous channels for drainage
- deeper growing medium but overall not significant extra weight on the roof
- biophilic: emulates riverbed and bank, m ore naturalistic feel for onlookers than uniform turf
We’re getting great responses from clients about this approach and think we’ll be doing a lot more of them. And it really lends itself to Revival work which we now deliver through our sister company Green Roof Revival Ltd. We’ve had some collateral made up with information about the build up and weight, and images of roofs we’ve done in this way.
There’s a screengrab below to get you started. Please send an email or request via contact for the full pdf