Creating the Living Roof

The addition of the straw bale house also has a living roof on both sections of the house. With 4 foot overhangs on the south walls and 3 feet overhangs everywhere else, the two levels of the new section total 2,000 square feet of roof over 1,100 interior square feet. Both roof lines have an element of curvature over the 25′ sections running east/west, and are otherwise flat over the 15′ depth.

We elected to go for a torch on roof underneath our soil, rather than the pond liner that we used on the first build. Over that, we laid out the vapour barrier plastic and then rolled out the drain mat. Also at some point, Colin fitted the flashing over the lip of the roof in one foot sections. We also added drain rock to the roof sections that are under the overhang, and made gravel beds around the drains that funnel into the downspouts so those areas don’t get clogged up with dirt and roots.

Next was the job of loading soil onto both levels of roof. We had our friend and neighbour come over with his excavator, and he loaded up his bucket and lifted it onto the lowest corner of the roof. More friends and neighbours then transferred buckets of soil up to the second roof, also at the lowest point, which was then spread out by more amazing friends and neighbours. Our depth of soil was set at 3 inches, calculated by our building engineer as the weight capacity for the roof based on the framing structure we used. The soil type we used was simply a mix of local sand and soil.

I waited until the fall to begin planting, as I didn’t intend to do any watering. Mostly the plants collected were from the first roof we planted, which was rather fully grown and could use some thinning. Many of the local sedums were lifted from the rocks on either side of the house, but also we were gifted with succulents thinned from crowded patches from friends’ gardens. There were spaced about 4 inches apart, with each variety planted separately inside linear sections that I imagined flowing across the curves of the roof, so that eventually when they are filled in, the colour diversity of the plants as well as the flowering times and colours will show up as differentiated sections. Eventually it may be too time consuming to keep the plants inside their own sections and succulent chaos will rule. Each following spring and fall I have added to the planting, thus, it has taken 2 years to get the roof covered, although not filled in. 2,000 square feet is a lot of plants.

Varieties include- ice plant, sempervivum (hens and chicks), sedum spurium, broad leaved stonecrop, oregon stonecrop, spreading stone crop, and various other sedums of unknown names. These two new roof sections are visible from inside the house, as each floor is stacked like a terrace down the bedrock, which makes the prospect of design and colour more interesting. Our first living roof is not at all noticeable except from a place outside and to the east of the front door, which is not a highly used space, and so the plants on that section are rather unattended, which suits us just fine. I am happy knowing that the ground space our shelters occupy is not being wasted on the birds and insects that might have otherwise foraged for food in it’s space. Each morning I watch as the chickadees tumble all over the roof, and in the summer the bees cling to the range of variously flowering plants. It is reassuring to know that we can continue to provide habitat for those that live side by side us in this world, while we clear hillsides and raise buildings in the pursuit of comfort.

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