This is a post about my experience in our green roof construction in fall 2012.
We started our construction in September. The first day was to assemble the membrane. This membrane was used for waterproofing, and it can project the roof itself too. We used a very bad smelling chemical liquid to seal the seam. I had to brush the sand away from the seam before other students spread the seal on the membrane, so the sand will not damage the seam area. Then we used adhesive tape on top of the seal after it dries out to strengthen it. I was kind of wondering if they can prevent the water from flowing into underneath, but I figured the seal could make it work better.
The first step was finished quickly, while the pavement took us a little bit longer. We used the 2’*2″ interlocking rubber tile as pavement, paving them from the door all the way to modules, and using them inbetween modules, I think they can better protect the membrane. Those tiles have holes on the side, so we used a stick fixer to connect two tiles. The fixers are easy to push in and hard to pull out because of the teeth on them. While, the holes on tiles were so small to push the fixers in, and it gave us a hard time to assemble the tiles, finally we began drilling holes on tiles. When I searched the interlocking tiles I saw some jigsaw puzzle piece like tiles, I think they are easy to assemble. Maybe we couldn’t find that kind of product, but I finished the pavement anyway.
The next step was for drainage layer and soil. We went to the green house to assemble them. We first put the expanded clay on the bottom of modules. We should allow the drainage holes on the bottom of the module to show so it can drain the excessive water. Next layer is the root barrier fabric, and then goes the soil. I saw the name on the bag was playing sand, I figured professor would want to use the soil that could be a little bit harsh for plants to grow on, because it looked not rich in nutrient. But I think sand is more good for drainage, so the water will not stay there for very long. The soil depth is approximately 3″-4″ which I measured later.
Finally we can plant the plants on the roof, so it really can be a green roof. I helped with plant propagation in the summer. We just cut a stem from the plant and sticked it in the soil, and we used the mixture of sand and gravel. I was suprised that Kirk told me they can survive under this condition! I remember we planted Sedum album f. ‘Murale’. In this project, we planted five types of plants in each module with 4″ spacing and 5 rows*5 columns. I saw some of them were large and tall, some are so small, I was wondering if the small ones can survive with a large strong neighbor, so I was more careful with those large ones to prevent them from hindering the small plants. I always wetted the soil before planting, but I found that it took a while for the water to prenetrate the soil and water only stayed in the topsoil if I only water it once. I had to wait for a while before the second round watering. I tried not to damage the root when I pulled the plants out of the strips, and I basiclly used my hand to dig the hole for planting, and everytime my nails were left with soil in them after I washed my hands several times! This is a extremely labor intensive work, and I wonder if other green roof constrcutions always have people plant plants on site by hands? Right now we have finished all the sedums, we are on mixed planting now, and final round would be herbaceous. We may not be able to finish all the planting this semester, I hope we can finish it in the next semester soon enough.
The drainage system is really simple enough to understand, which is not what I expected before. I thought we would have the one like Houston’s green roof, an advanced system. I did not participate in that part, but I learned something from Chelsea’s post.
I really appreciate this opportunity to participate in a real green roof project. We have been taught many times about the structure of green roofs, so I think I am quite familiar with them. But I found that I could not really understand it and remember it if I were not in this project. I had to ask Kirk to explain to me every steps and materials we use. When I told my colleagues about the construction, I thought they would knew it since we had learned it before, then I realized you had to see it to really understand it. From this project, I also learned some details of every steps which I have tried to described above. We will have the atmospheric data measurement equipment installed to collect data of temperature, wind speed and others. I found that a simple research really takes whole lots of people from different backgrounds to involve in. This green roof project is related to landscape architecture, horticulture, and atmospherical schience, which is big than I thought. I hope our work can contribute some valuable information to green roof research!