Timber frame with a strawbale insulated green roof

Here's a build we did this summer, that came about as a result of a crowdfunding campaign to build a teaching space at the back of our stone cottage. The frame is a mix of milled spruce and larch, with a larch cladding. The roof is a strawbale insulated, membrane covered green roof that uses a mix of turves and loose soil. The whole roof is designed to channel water down to the two front corners where it can be collected. The 6x2 frame is first insulated with a variety of leftovers from other projects, and will have non loadbearing strawbale on the inside which we'll earth plaster. Warmth comes courtesy of a rocket mass heater, although the build faces south so we'll get some passive solar gain, even here in Northern Ireland.



The roof has a lot of layers, starting with sarking boards made from sawmill skins, then a breather membrane, on top of that are 90 bales of straw, then a 1.2mm butyl membrane, 2 layers of silage sheet (just in case), a good layer of old carpet, and then soil, which is approx 3 inches thick. The edges of the roof have a slight gutter formed by the fascia sticking up a couple of inches, behind which is coarse gravel.

The strip windows are made from sheets of bulletproof glass that came from a local bank that was being stripped out, and all the rest of the windows and doors were destined for landfill. When we're done there will be a front deck below the overhang.

and here's the build sequence -

Awesome build steve ! Thanks for sharing. Remember, everybody that builds a good working RMH spends inordinate amount of time just admiring it . You built a kickass room at the same time! Enjoy !

Nice! Too bad somebody beat me to giving an apple, lol!

when I think of earth roofs i think of the underground house dvd course and he sugest always have solid earth for runoff to go, but ive seen lots of shelters where the rain runs off the corners but what prevents those corners from eroding?

We made the fasica boards at the edge a couple of inches higher than the surface behind, and then put some gravel around the edge, about 3 or 4" wide. At the corners there's a hole drilled and the rubber membrane pushed down into it, with a bit of 1" pipe pushed into the hole. The water finds the gravel 'drain', and gets directed to the corners where it can run down and we can do something useful with it. Until we get some root structure in the soil, then its going to be prone to washing toward the lowest point, so until then its just a case of keeping an eye on it and repairing. Even coming into winter, that bare earth won't be bare for long, and once there's growth up there it will all stay where we want it to.