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FOTD living green roof

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ENGR215 Project Page in Progress
This page is a project page in progress by students in Engr215. Please refrain from making edits unless you are a member of the project team, but feel free to make comments using the discussion tab. Check back for the finished version on {{{1}}}.


The purpose of the project was to educate Nature Center visitors on the benefits of living green roofs, to enhance the aesthetics of the Nature Center, and to inspire others to build their own green roofs. The Dune-Gineers Green Roof was built at the Friends of the Dunes Nature Center by students at Humboldt State University Engineering 215 class.


The Friends of the Dunes is a non-profit organization, and they work to protect and preserve the natural habitats of the dunes. Their Coastal Nature Center is a place where they promote green solutions by educating visitors. Construction started on the nature center in 2007, and there are still a few outstanding projects that need to be completed. One of the projects is a green roof on the west awning. As part of the Engineering 215 course, we were given the opportunity to design the green roof and build an educational model of it.

Problem statement

The objective of the project is to design a green roof for the western awning at the Humboldt Coastal Nature Center, and to build a model of the green roof that educates visitors and enhances the aesthetics of the Center.

Problem Analysis and Criteria

Criteria Weight Description
Aesthetics 10 The roof must look as professional as the rest of the Nature Center.
Local Suppliers 9 As many local businesses as possible.
Cost 3 Entire design must cost less than $400.
Weight 5 The roof must weigh less than the roof can handle. The lighter the final design, the better.
Safety 5 Must be designed to be accessible for maintainable and weeding.

The Solution

Describe the design and the model

Western Awning Green Roof

Using the criteria and their respective weights, we picked an option that although is slightly more expensive, looks professional and allows plants to survive in the summer. It has a low weight, and can be built without threatening the structural integrity of the building. Plastic Bend-A-Board is used for the retaining wall, with the components of the green roof layered behind. Hydrostop waterproofing paint is applied once more to roof to ensure the roof will not leak. The base layer of the roof is a protection fabric to stop roots from growing into the roof, and is followed by a synthetic drainage layer. The synthetic layer is a light material, and with its many pockets to hold water, will keep the roof green during the dry months, while removing excess water during the rainy months. On top is a filter sheet used as the separation layer. Four inches of native soil used as the growing medium is placed on top of the filter sheet. An erosion control blanket placed on top of the planting medium stops the soil from getting blown off or washed away during winter storms. It is made of a biodegradable material, and is only expected to last until the plants are big enough to hold onto the soil themselves. A micro sprinkler system is installed on top to provide water during the summer. These layers of the roof stop water from pooling on the roof, and create a habitat on top in which native plants can thrive.

Model of the Green Roof

Description of the Model


Describe the costs section

Western Awning Green Roof

Here are the estimated costs for the Western Awning:

Material Qty Source Extended Amount($)
Hydrostop 1 bucket On site Free
Protection Fabric 500 ft sq Conservation Technology $357
Drainage Plates 500 ft sq Conservation Technology $905
Separation Fabric 500 ft sq Conservation Technology $267
Plastic Edge 100 ft Ace Hardware $70
Erosion Control Blanket (CS3) 500 ft sq Western Excelsior $180
Sprinkler System 500 ft sq Home Depot $113
TOTAL $1700

Model of the Green Roof

The costs of the materials used for building the model green roof are:

Material Qty Amount ($) Extended Amount($)
Plywood Board 24 sq ft $26.88 $26.88
Pine Pole 2 $9.99 $19.98
Concrete Anchor 4 $2.99 $11.96
Post Anchor 4 $4.89 $19.56
Framing Anchor 2 $0.39 $0.78
Waterproofing Paint 1 $11.59 $11.59
Paint Brush 1 $3.49 $3.49
Bend-A-Board 1 roll $19.99 $19.99
Drainage Rocks 1.5 cb ft $19.99 $19.99
Soil Mix 1 cb ft $7.99 $7.99
Rubber Mat 24 sq ft $35.94 $35.94
Filter Fabric 24 sq ft $6.00 $6.00
L Brackets 32 $0.49 $15.68
Bolts 4 $1.49 $5.96
Washers 8 $0.23 $1.84
Nuts 4 $0.23 $0.92
Screws 1 box $3.69 $3.69
MGV PHL Deck 1 $6.00 $6.00
Rubber Adhesive 1 $10.99 $10.99
Strap hanger 1 $2.59 $2.59
Plexiglass 4 by 8 in $1.20 $1.20
Tax 7.25% $16.17
Total $239.19

Labor Hours


How we built the model. Have pictures.

Instructions for Implementation and Use After installation, more plants will need to be added to the roof. These can be added by carefully planting on the roof, or by spreading seeds under the erosion control blanket. Extra heavy watering will be needed initially to get the plants established.

Periodic Watering When the plants on the roof look wilted or there has not been any substantial rainfall, the roof will need to be watered. This can be done by turning on the spigot on the north side of the building, two feet of the ground. Water should occur no more than twice a week, and for only twenty minutes.

Yearly Cleaning The maintenance of the green roof will require occasional pulling of weeds, cleaning of drain gutter, and inspecting of the sprinkler heads. Quarterly flushing will require approximately one to two hours.

Safety Precautions As the blocks on the side of the roof are not attached to anything, great care should be taken when accessing the roof. A 12 foot or higher ladder is recommended.

next steps

We are looking forward to building the roof!