Underhill House now has the hopefull beginnings of a sod roof.
This has not been an easy project!
I call it a saga of dirt, sweat and tears.
The tears are mine. They are tears of frustration.
I’ll get to that later.
Our roof undulates with the natural curves of the unmilled trees that make up it’s timber frame and rafters. It’s flowing lines are a thing of beauty and have been an engineering challenge every step of the way. It is very well insulated with many non-conducting layers including blown in castor bean oil foam that was topped with wood decking and a layer of old billboard tarps and a layer of the kind of rubber sheeting used on flat roofs and under the ponds people make in their yards. And over that was placed another layer of old billboard tarps to protect the rubber membrane for the winter.
The roof wasn’t ready to plant until it was too late in the fall. If we had put the soil on the roof without planting, it would have been blown away so it went through the winter like that. And it worked very well at keeping in the heat! Our passive solar and solar hot water heat system and great insulation kept the house comfy with very little need for the propane backup we have built into the system.
But there is another kind of protection a roof need to give in the summer — keeping the heat out instead of in. Something tells me our summers are not going to get cooler. That is where we are counting on the sod roof. The 3 inches of soil and plants will not only provide thermal insulation — the plants will absorb that solar energy beating on its surface and photosynthesis will transform the blazing heat into more plant material.
It’s a lovely idea, and we were ready to help pioneer a workable, growing roof.
Our builder, WholeTree Architecture and Buildings has done some growing roofs before, but none quite as big or high in the air as Underhill House, and that meant we were all winging it. Doug and I researched what to plant up there, what kind of soil to use and how to get it up on the roof.
For plants, we consulted extensively with Neal at Prairie Nursery and decided to grow two prairie grasses in the 3″ of soil on the roof — June Grass and Side Oats Grama Grass . We picked these because they will need very little watering. Once they are established, unless we are experiencing true drought conditions, they will just go dormant when the weather is dry. When we get more rain, they will spring back to life.
Our other choice of no mow fescue, would need more watering. When ever the weather gets dry, it could quickly go beyond dormant to dead.
Fescue is that it is easer to start. Prairie grasses, though they are very touchy to establish, should be a more sustainable solution long-term.
For soil, we opted for screened soil mixed with compost and sand from Keleny Top Soil.
in Madison. Our normal source for all the gravel, sand, Ivey’s on Mineral Point, was like most top soil providers in the area — they keep their soil outside, and it was too wet to move. Keleny keeps some soil under a roof, so it is ready to go. It was also screened, so that it would be poured more easily.
Then a layer of discarded and recycled wall to wall carpeting went on to provide more gripping surface for the dirt and protect the rubber membrane. ost people replace their carpet because Fifi had a bladder problem, but that should just make them more attractive to plants.) We have been VERY careful not to puncture that membrane.
Last Monday the screened dirt arrived. To get this fine soil on the roof, we needed a crane to hoist it up in a giant bucket. We turned to McCutcheson Cranes in Dodgeville just 10 miles away.Tuesday morning the crane was trucked in. It was a challenge to find a good place to anchor it, and the most secure spot to set up the crane did not allow Mike McCutcheson to see what was going on the roof, so Doug took the task of giving him hand signals about where to swing each bucket full.
We had estimated we would need about 17 cubic yards for the roof, and since the truck holds 21 yards, we asked them to bring a truckfull, expecting to use the rest on the ravaged ground around the building site.
Unfortunately, the roof gobbled up just about all the screened soil.
Over the course of the morning, as soil was dumped on and smoothed out, it became impossible to tell how deep it was in any given spot – because of those lovely undulations. So the men underestimated how close to 3 inches of soil had been haulted up and opted to leave the last bucket or two on the ground.
So far so good —
but we are coming to the tears part now.
Sitting next to the was a big pile of clay that has been abandoned there since last summer when our plastering team decided that this particular clay would not work on our walls, and they used a different clay for the job. What to do with this pile of clay has been a puzzle. It can not be spread over the ground. It can’t be put in the garden.
It is the kind of clay used to seal walls and make pottery. Though it looks a lot like soil — it is not soil.
Suddenly Roald Gundersen of WholeTrees began talking about putting that clay on top of our roof.
This came out of nowhere and completely dumbfounded me. He seemed to suddenly realize that something would be needed to hold down the erosion mat that goes on over the seed. He decided on the spot that it should be this clay.
I have been trained as a Master Gardener and had just been re-reading the extensive section on soil in my Master Gardener training materials because the soil where we are planning to plant our vineyard has been proving problematic. I was painfully, excruciatingly aware of negative consequences of dumping clay — even just “sprinkling” it as Roald wanted to — on top of prairie seed smaller than sesame seed.
I spent our lunch time trying to talk him out of it, but I could not. (If this were written on paper, there would be tears of frustration smearing the ink here.)
Against my express wishes, buckets of clay were hoisted onto the roof and dumped on two tarps.
Then we got to work preparing to seed.
Our first task was to make sure we had a soil depth of 3″ all over the roof. This was a laborious process of sticking pencils marked at 3 inches with tape into the soil over every few feet of the roof. I did a lot of the bending over and applying my depth guage and marking areas which Doug, and our two assistants hauled dirt to bring the level up to 3 inches.
At first, they were able to take dirt from the hollows in the roof, which were much more than three inches deep, but eventually, they had to go back to the remaining screened soil left on the ground, wheel barrow it around the house and haul it up the ladder by hand in 5-gallon buckets. I don’t have any photos of this process because we were all working too hard. I estimate that somewhere between 30 and 40 buckets were hauled up and distributed.
Finally we were ready to sow the seed.
The seed for the entire roof amounted to a mere 2 cups of June Grass and 11 cups of Side Oats Gramma Grass. To spread it evenly, it had to be mixed into a lot of saw dust. Fortunately, we have a vast supply of very fine sawdust from when we had a portable sawmill on site cutting some of our trees into the boards for the roof and the slabs for the window sills and counter tops. We divided the seed into two halves and mixed each up in our power wagon.
That was my job, and it was a treat. Running your hands and arms through cool, damp sawdust again and again is a very pleasant feeling. I found it soothing. I needed to be soothed. I was still steaming about putting the clay on the roof.
Doug and I carefully spread out the seed on the roof in 8-foot swaths from east to west. The planting instructions say rake the seed into the soil and then press it down with a roller to create good soil/seed contact.
There was NO WAY we were hauling a heavy roller up on the roof, so we stepped it in very methodically covering every inch with firm foot falls, although at the very edges, we reached our foot out while leaning away from the drop off. That area didn’t get such good compression. Couldn’t be helped. Safety first.
Then the 8-foot erosion mat was rolled out over the seed.
THE BAD NEWS
Then Roald sprinkled shovels full of clay all over it to “hold it down.”
It hurt me to watch him.
We got about halfway done by about 5. We were all seriously exhausted and starting to wobble in the brutal heat (mid 80s). Wobbling on the roof didn’t seem like such a good idea, so we quit for the night and had a beer.
Later that evening before full dark, a huge storm came up on the horizon. The wind was whipping, and pounding rain seemed imminent. I climbed back up on the roof with chunks of sand stone from where the hill was dug out for the house and placed them strategically. As I stood on the roof watching, the ominous, dark green clouds passed just to the south of us, and all we got was some medium wind and a bit of rain.
Wednesday, Roald came back with a couple of assistants. He threw the sandstone pieces off the roof, and we finished seeding, matting and shoveling clay clumps onto the roof.
Yesterday morning Doug and I woke up wind howling around the house. We quickly climbed to the roof to find that the whole south edge of erosion mat had already peeled back over a foot from the wind – which was building. The matwas ready to start rolling further. Doug carried the rocks back up by the bucket full, while I crawled along the edge of the roof rolling the erosion mat back into place and setting rocks all along the south edge.
That brought me as close to that south edge as I have ever come. It’s the farthest drop down on the roof, and it gave me a lot of respect for all the work that has been done on that roof by the carpenters as they built its many layers.
The storm once again spent most of its fury to the south of us, but the rocks held the mat in place. Away from the edge, the mat seems to have interwoven along the 3-4″ overlap between panels and is holding well.
So I’m hoping that the rocked-down erosion mat will continue to hold, and the grasses will germinate and grow. I do not have high hopes for all the places where there are clumps of pottery clay sealing them from water and making a barrier which may be too hard for their tiny spikes to penetrate.
Ironically, my book group is about to discuss When Women Were Birds by Terry Tempest Williams. She was raised Mormon, and much of the book is about her experience of how women are often ignored to the point they felt they had no voice. While I was reading, I felt glad that I haven’t had that awful experience — suddenly I felt like a chapter in the book.
Today as I was driving to Madison I watched young grasses about a foot tall ripple in the wind like waves on the water. I hope our roof will look like that by end of summer.