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[[File:roof_finished.jpg|thumb|left|500px|Living Roof. Image credit: A.R.Shearer]][[File:roof_finished_01.jpg|thumb|right|500px|Living Roof. Image credit: A.R.Shearer]][[File:roof_finished_02.jpg|thumb|right|500px|Living Roof. Image credit: A.R.Shearer]] | [[File:roof_finished.jpg|thumb|left|500px|Living Roof. Image credit: A.R.Shearer]][[File:roof_finished_01.jpg|thumb|right|500px|Living Roof. Image credit: A.R.Shearer]][[File:roof_finished_02.jpg|thumb|right|500px|Living Roof. Image credit: A.R.Shearer]] | ||
==Abstract== | ==Abstract== | ||
Revision as of 18:29, 17 May 2015
Abstract
Humboldt State University Engineering 305 class volunteered to construct a living roof for Bayside Park Farm a community farm in Arcata, California. The roof was designed to be placed on top of an animal hutch that the farm was currently in the process of building. The type of living roof is considered to be a form of an extensive living roof, due to the fact that it allows for low maintenance and ease of construction. Currently, the living roof seems to be serving its purpose as a roof for the animal hutch.
Background
Bayside Park Farm located in Arcata California in Northern California in the United States and also goes by the name Arcata Educational Farm. It is a Community Supported Agriculture (CSA) facility that also acts as an educational farm. The Engineering 305 class during the North American Spring 2015 semester will be constructing a functioning living roof. This living roof must attend to the owner's specifications regarding its dimensions and purpose, which are that the living roof be made on a small animal hutch that is currently being made. The construction and development of the living roof will span from January 2015 until May 2015.
Problem statement
The objective of this project is to create a functional, sustainable and sufficient living roof at Bayside Park Farm. A living roof also known as garden roof or green roof, is a roof that provides protection to the roof base and helps reduce water runoff and allows for some temperature regulation inside the housing unit. Furthermore it can be used for improving air and water quality, promoting energy conservation, providing food, and creating an ecosystem within an urban area. If possible we plan on using affordable or recycled materials that may be donated for the roofs construction and by doing so we will cut costs down for the construction of the roof. By doing this we aim to create a feeling of community involvement and create another area of the farm that may teach the community about an alternative to roofing.
The original suggested project was to build a living roof over a cob oven that would be rebuilt. However, at the request of the farm our project was changed to building a roof for a future animal hutch that the farm was wanting to build.
Criteria
The criteria was defined according to the farms purposes and preferences, which were very loose and only asked that the roof serve as an educational tool that could be used over time. This criteria was used as a guide for the construction of the roof. Where values were higher is where the most effort was placed in providing those demands in the construction of the project. The scale (1-10) represents the importance level of the constraint of each listed criteria.
| Criteria | Constraints | Weight (1-10) |
|---|---|---|
| Functionality | Must serve recreational and educational purposes. | |
| Safety | Must be able to hold while put on a structure. | |
| Durability/Resistance | Must be weather resistant. | |
| Maintainability | Must be low and easy maintenance. | |
| Aesthetics | Must be pleasing to the eye. | |
| Weight | Must be able to hold at least 20lbs per square meter. |
Literature Review
Living roof basics
The basic components of green roof systems are waterproofing, soil and plants. It really is that simple. The combination of these material is easy and the success of all living roofs depends on the types of plants used and an understanding of how these combined materials will work.[1] An understanding of the type of environment the roof will be located in is also important for the success of any living roof. For example here in Humboldt County earthquakes pose a risk as well as a high precipitation level in the fall and winter months, however in the spring and summer months there is little to no rain fall. Design should account for earthquakes and the forces it will create on the building as well as any irrigation or drainage components that will function during both during the wet season and dry season. These however are design features that should be asked when building the structural support and housing unit the living roof will be placed on top of before and during construction of both the roof and the house or structures for the roof. For the purpose of our project we were only asked to concern ourselves with the construction of the roof itself because the farm would be responsible for the hutch or housing unit and the structural support. This means we focused on the weather aspect of design for the roof. Living roofs are that simple especially for small designs. Living roofs are becoming increasingly popular in North America and are starting to show themselves in large scale industrial buildings. The design and construction of those types of roofs are a little more complex and a lot more labor intensive, but the end result is worth the effort
Living roof concerns
A main concern regarding living roofs revolves around the types of vegetation that is being used because the performance of the living roof is the plant communities. Concerns regarding the plant communities on living roofs deal with weather factors such as wind stress and over exposure to the sun, however in the literature the main focus has been on wind stress because plants are not generally accustomed to the heights that roofs generally are. There has been some practice of using native plant species because they are generally most accustomed to the region the roof is. However, in some of the literature discusses native plants not working on extensive living roofs because of the shallow soil depth generally found on extensive living roofs.This then means that not only is wind stress the main factor in determining the types of flora being used but that the rooftop itself is challenging for the survival of plants.[2]
Another more recent concern that has appeared during the increased popularity of living roofs is water-quality of the storm water runoff from living roofs. The literature suggestes that living roofs may act as another source surface-water pollution primarily because of the nutrient content found in the growing medium and soil used. [2] To combat this we tried to use soil and growing mediums that not only would maintain the health of the plants but that were already found on the farm. We went with a perlite and coco peat combination.
Types of Living Roofs
In the world that is living roofs there are generally two types of designs. They are intensive and extensive. More recently there has been the inclusion of a hybrid living roof that is a combination of these two types called semi-extensive.
Intensive
Intensive living roofs are found on industrial building such as parking garages or other public buildings usually heavily trafficked by humans. Intensive living roofs have a very high plant diversity because these roofs have the ability to provide very deep soil potential for these various plant communities.[3] Intensive living roofs may be viewed as actual gardens on roof structures not just because of the plant diversity but because those plants are maintained on an individual basis similar to what is found on ground level. [4] This also means that intensive living roofs have irrigation systems built into the living roof system. The combination of these two things makes intensive living roofs very high maintenance physically and monetarily.[5][6]
- Here is a useful advantages and disadvantages look at intensive living roofs that may express the concept a little easier. [5]
| Advantages | Disadvantages |
|---|---|
| Diversity of plants | Greater weight load on roof |
| Good insulation properties | Need irrigation and drainage system |
| Simulate wildlife garden | Greater weight load on roof |
| Attractive aesthetically | Need irrigation and drainage system |
| Accessable/recreation | High maintenance and cost |
| Longer membrane life | High maintenance and cost |
| Storm water retention capability | More complex |
Extensive
Extensive living roofs are low maintenance roofs because this design type is used most often used with lightweight and low height buildings. The soils in extensive living roofs are generally shallow. [3]Especially much shallower than intensive living roofs because the plant communities in extensive living roofs tend to be self-generative plants or types of plants that can survive in some sort of “desert” like environment.[4] Some types of plants may include shrubs, grasses, mosses, and indigenous plant species.[6]
- Here is a useful advantages and disadvantages look at extensive living roofs that may express the concept a little easier.[5]
| Advantages | Disadvantages |
|---|---|
| Lightweight. Generally no reinforcement | Less energy efficient |
| Suitable for large areas | Less storm water retention benefits |
| Roof slope 0degrees-30degrees | Limited choice of plants |
| Long life and low maintenance | Not accessible for recreation or other uses |
| No need for irrigation or specialized drainage system. | Unattractive usually in the winter season |
| Inexpensive | |
| Vegetation can grow spontaneously |
Semi-Extensive
There is more information on semi-extensive living roofs out there, but the main idea behind the design is that it is low maintenance like an extensive roof, but has deeper layers for growing medium like an intensive roof has. Meaning high diversity of plants with low-input.[3]
Living roof design
The design of a living roof depends on the wants and needs of those requesting one for their home or industrial units. A living roof should be viewed as another artistic expression of self because they can be built, placed, and designed in a manner that expresses either the designer or the one inhabiting the structure. However, the one aspect of living roofs that generally has laid out plans or rules that should be followed are the different layering components of living roofs.[1]
- Here is an example of generic layering usually found on industrial living roof systems. Some of these layers may be applicable to smaller scale roofs.[7]
| Layers | Description |
|---|---|
| Deck Layer | Is the foundation of a green roof and may be of concrete, wood, metal, plastic or a composite material |
| Leak Detection System (optional) | Leak detection systems are often installed above the deck layer to identify leaks, minimize leak damage through timely detection, and locate leak locations. |
| Waterproofing Layer | Very important to prevent water damage through the deck layer. This layer must be entirely waterproof and long lasting. Several waterproofing materials can be used, like thermoplastic membranes, elastomeric membranes, modified bitumen polyvinyl chloride (PVC), applied rubberized asphalt, built up bitumen and others. The waterproofing material may be loose laid or bonded, which is more recommended. |
| Insulation Layer(optional) | Usually located above, but sometimes below, the waterproofing layer. Its function is to increase the energy efficiency. Recommended for metal roofs |
| Root Barrier | Used to protect the waterproofing membrane from root penetration |
| Drainage Layer | Placed between the root barrier and the growing media to remove excess water from the vegetation root zone. Must consist of synthetic or inorganic materials. The thickness of the drainage layer type is an important design decision. For extensive green roof systems, the depth of the drainage layer usually varies from 0.25 to 1.5 inches thick and increases for intensive designs. |
| Filter Sheet | Consists in a “semi-permeable needled polypropylene filter fabric placed between the drainage layer and the growing media” in order to prevent the drainage layer to clog by the migration of some particles from the media into it. The filter sheet must allow the water migration into the drainage layer |
| Growing Media | Usually 3 to 6 inches deep and composed of approximately 70 to 80 percent lightweight inorganic materials like clays, pumice, scoria or other similar materials. The remaining media must not exceed 30 percent organic matter because it can transport nutrients into the runoff from the roof and clog the permeable filter sheet. |
| Plant Cover | It is the top layer and consists of plants that are non-native, slow-growing, shallow-rooted and perennial. The selected plants must be able to withstand harsh conditions at the roof surface. For drought periods it is recommended the installation of a watering system. |
Construction
The construction of the roof took a combined total of four days with the effort of two people at a time.
Design
The living roof was designed based off the information given by the farm that the hutch being built would be a 4.5ft by 4.5ft structure. We were not told anything else about the hutch being built other than its proposed size. Because of the size of the roof it seemed practical to give the roof no more than a two degree slope to prevent soil erosion and allow water to drain naturally. Because we knew nothing of what the structure would look like we assumed an overhang of about three inches. The roof was asked to be built as low maintenance as possible therefore a simple one inch open was allotted for the back of the roof to allow water to flow backward naturally.
- We used this equation to determine the weight of the roof itself so that the structure may be built with the weight in mind.
- Here are the layers of the roof design being built.
| Layers | Description |
|---|---|
| Rubber Membrane | This first layer protects the wood from any moisture and prevents any leakage. |
| Pond Liner | This layer protects the rubber membrane from any moisture exposure. |
| Drainage Rocks | These rocks will allow the drained water to run-off slower. |
| Lava Rocks | These were used because they will allow the water to pass through easily. There will be no water build up or blockage which may cause any type of root rot or flooding compromising the layers. |
| Landscaping Fabric | The fabric is a permeable material that will prevent the soil from blocking the drain rocks or lava rocks. Without the landscaping fabric the water would not be able to drain properly which may cause root rot. |
| Perlite | This will add water retention. |
| Coco Peat | This soil has very low nutrients, but is very good at maintaining moisture. |
| Plants | Succulents were the desired plant of the farm. |
| Lava Rocks | These were used again, but this time as a soil protector instead of wood chips because the wood chips have the potential to increase the soil acidity. |
- Here is a crude example of the layers placed on the roof.
- Here is the design the roof is based off of.
How to Build
Video
Timeline
| Weeks | Tasks | Observation |
|---|---|---|
| 16-Fev | Roof sizing design (figure out dimensions and establish the adequate amount of materials). | |
| 23-Fev | Listed all needed materials and their looked prices. | |
| 2-Mar | Finalize the budget and start looking for donations. | |
| 9-Mar | Look for donations (delivering donation letters). | |
| 16-Mar | Look for donations (delivering donation letters). | |
| 23-Mar | Look for donations (waiting anwers from potential donators). | Got the donations. |
| 30-Mar | Transport materials to the farm and start preparing the wood. | Wood without treatment, had to treat before constructing. |
| 6-Apr | Build the base of the roof. | The farm provided the foundation. |
| 13-Apr | Put on the first layers (protection/root barrier and waterproof layers). | |
| 20-Apr | Finish putting the layers (drainage, filter layers, growing media and planting). | |
| 27-Apr | Verify functionality (check if the plants and the structure are okay and look if there is any problem). | Plants seem to be adapting well. No sigs of leakage. |
| 4-May | Verify functionality (check if the plants and the structure are okay and look if there is any problem). | |
| 11-May | Verify functionality (check if the plants and the structure are okay and look if there is any problem). |
Costs
This is the budget for the roof. Almost all of the items were donated.
| Quantity | Material | Source | Cost ($) | Total ($) |
|---|---|---|---|---|
| 1 | Pond liner-10ft x 12ft | Donated by Pierson Building Center | 70.00 | 00.00 |
| 1 | Landscaping fabric-3' x 25' | Donated by Pierson Building Center | 09.00 | 00.00 |
| 1 | Soil-28L | Donated By Farm | 05.00 | 00.00 |
| 1 | Growing medium-4 cubic ft | Donated by Pierson Building Center | 19.00 | 00.00 |
| 1 | Wood Glue-18oz | Donated byPierson Building Center | 06.00 | 00.00 |
| 36 | Stainless Steel Wood Screws | Donated by Pierson Building Center | 00.85 | 00.00 |
| 1 | Wood Preserver Paint-32 oz | Donated by Pierson Building Center | 10.00 | 00.00 |
| 1 | Rubber membrane-5' x 6 ' | Donated by Pierson Building Center | 32.00 | 00.00 |
| 1 | Shower Pan Liner Adhesive-16oz | Donated by Pierson Building Center | 09.00 | 00.00 |
| 5 | Wood | Donated By Farm | 00.00 | 00.00 |
| 8 | Plants | Donated By Farm | 00.00 | 00.00 |
| 1/4 | Landscape Rocks a yard | Donated by Miller Farms Nursery | 67.00 | 00.00 |
| 1 | Drop cloth 9'x12' | Ace Hardware | 03.99 | 03.99 |
| 1 | Paintbrush 3" poly | Ace Hardware | 02.99 | 02.99 |
| 1 | Paintbrush 2-1/2" poly | Ace Hardware | 02.79 | 02.79 |
| Total Cost | $10.58 | |||
Operation
Maintenance
The roof was designed specifically for low maintenance therefore the farm will have to do some weeding and if required some watering. However, side paneling was placed on the structure and that was not accounted for in the roof over hang calculations. This means that when the roof drains water the back paneling is getting wet because the structure is now extended out an extra three inches. Making sure that back paneling wood does not rot or mold is pertinent to the health of the system.
Schedule
For the functional longevity of the roof the farm should do minor maintenance as suggested.
- Daily
- A soil finger test maybe done to make sure the soil is not too dry.
- Weekly
- A soil finger test.
- Check on the health of the plants. Curb any growth that may hinder/puncture the membrane.
- Check for any leakage.
- Check for any membrane/pond liner tears or punctures.
- Check back paneling if rain has fallen because it is possible the wood may rot or mold.
- Weed if necessary. making sure to pull anything that may have a long tap root.
- Monthly
- A soil finger test.
- Water.
- Any weeding. Making sure to stop the growth of anything with tap-roots that may compromise the membrane.
- Check back paneling if rain has fallen because it is possible the wood may rot or mold.
- Yearly
- Harvest succulents if desired.
- A soil finger test.
- Check the life of the membrane.
- Check on any touch ups if they were done.
- Check back paneling if rain has fallen because it is possible the wood may rot or mold.
Conclusion
Testing results
Testing involved checking on the roof once a week to make sure the structure was still standing and that the plants were still alive. Testing also involved watering to check for any potential leakage. During the construction of the layers of the roof we had tested to make sure the slope tested on paper was actually appropriate for the roof. This testing consisted of us pouring water at the head of the roof once the first two layers (the membrane and pond liner) and drainage rocks were placed. This allowed us to see that gravity was working for us and that the slope was enough to allow for drainage. We did this same test after each subsequent layer to again make sure the theoretical slope would pan out with each layer.
The actual test was trying to simulate rain fall. This was done by trying to fill the roof with about 12 gallons of water. This proved very arduous and somewhat difficult. However, we were able to exam how the drainage worked and we were able to check the consistency of the water leaving the roof. We discovered that the roof does a very good job of draining the water and retaining some water. We also discovered that there does not seem to be any nutrient loss from the soil, but that because the lava rocks are red (full of iron, magnesium, and potassium) the waters discoloration seems to only be coming from that. Here is what those results looked like.
Discussion
The maintenance of the roof and durability of the roof seem to be withstanding. The succulents planted have started to take over meaning that thus far the soil depth seems to be permit-able for the succulents. There is a possibility that we could maybe try to go deeper with the soil there is some room currently to add just a few inches of more soil. Regarding the usage of lava rocks. There was some concern that the heavy metals from the igneous rock has the potential to seep into the soil maybe altering the nutrient level for the plants. With this testing result however, it seems that the water is leaching those metals out of the roof. This seems to be good news for the plants, but regarding the water run-off this could pose a potential problem to the grass or plants around the structure. This is actually one of the concerns brought up in peer-reviewed articles regarding living roofs and the amount of metal leaching from living roof structures. Testing of the surrounding plants and grasses of living roofs could be a next step.
Lessons learned
Adding more soil or rather having the soil flow over would maybe make the roof more aesthetically pleasing and allow for more root depth. We were lucky enough to use untreated milled wood for the roof base which is a lot easier to work with than particle board or pallets.
Next steps
The roof has placed side paneling that was not accounted for during the construction of the roof. We were not aware that this would be something that the farm would be doing. What this means is that the farm will have to make sure during the raining season that the back panel wood does not rot or collect mold because it is now getting wet by the water drainage. The farm will have to make sure that the roots being set by the succulents are deeo enough to withhold the strong winds during the spring season. The farm should maintain the plants and grasses surrounding the roof according to the amount of metals being released by the roof run off.
Troubleshooting
We do not for see any major problems. However, for minor issues we suggest:
| Problem | Suggestion |
|---|---|
| Pond Liner tear/weathered | Fix with pond liner tape |
| Membrane puncture | Replacing the membrane with an uncompromising piece. |
| Leakage | Attending to the problem immediately. If it is a membrane/liner issue replacing those pieces would be suggested. If it is because of wood rot or splitting then if possible replacing that piece of wood is advised. |
| Lava rocks as a soil cover | If the lava rocks prove hazardous to the health of the soil and/or plants replacing the soil cover with another organic material is required. |
| Back Paneling | The back paneling extends out to the roofs three inch overhang meaning the paneling is now being exposed to water. Making sure that wood does not mold or rot is important. If this happens either treat the wood or replace it. |
Team
Introduce team and semester in the following format:
References
- ↑ 1.0 1.1 Weiler, S.K. and Scholz-Barth. 2011. "Green rood system: A Guide to the Planning, Design, and Construction of Landscapes over Structure".
- ↑ 2.0 2.1 Oberndorfer, Erica, Jeremy Lundholm, Brad Bass, Reid R. Coffman, Hitesh Doshi, Nigel Dunnett, Stuart Gaffin, Manfred Köhler, Karen K. Y. Liu, and Bradley Rowe. 2007. “Green Roofs as Urban Ecosystems: Ecological Structures, Functions, and Services. (Cover Story).” BioScience 57 (10): 823–33.
- ↑ 3.0 3.1 3.2 Dunnett, Nigel, and Noel Kingsbury. Planting Green Roofs and Living Walls. Portland: Timber Press, 2008.
- ↑ 4.0 4.1 Lazzarin, Renato M., Francesco Castellotti, and Filippo Busato. 2005. “Experimental Measurements and Numerical Modelling of a Green Roof.” Energy and Buildings 37 (12): 1260–67.
- ↑ 5.0 5.1 5.2 Peck, S. and M. Kuhn. 2003. Design Guidelines for Green Roofs (PDF) (22 pp, 551K). Canada Mortgage and Housing Corporation and the Ontario Association of Architects
- ↑ 6.0 6.1 "Green Roof Systems: Intensive, Semi-Intensive, and Extensive.".Architect's Technical Reference. Accessed February 8, 2015. http://www.archtoolbox.com/materials-systems/site-landscape/green-roofs.html..
- ↑ "Hoffmann, G., Stack, R.C. and Wye, B.V. 2012. “Stormwater Management Guidebook”.