Shawn Smith

Instructor Jesse Peterson

Technical Writing

30 September 2015

DIY Build a Green Roof on Your Own Home

What is a green roof? A green roof or living roof is a roof of a building that is partially or

completely covered with vegetation and a growing medium, planted over a waterproofing

membrane.

What are the benefits of having a green roof?

Cleaner air

Growing food

Health Benefits

Filtered rain water

More roof insulation

Noise and sound insulation

In order to turn a roof into a green roof there are some things that need to be considered.

What building materials will be required especially if more support is needed for the structure?

What type of tools will be necessary?

Can the roof hold that much weight?

What type of plants should I plant?

How much will it cost?

Is the roof, flat or pitched?

Here is a list of the steps need to build your very own green roof. Before starting this project you

can look up your cities specific building codes on the internet or your city hall, to see if you can

build a green roof on your house. Some cities and HOA’s do not allow green roofs.

Step One

Assess what type of roof it will be built upon, flat or pitched. A flat roof is ideal for building

on but not required. See figure 1 below. No matter what type of roof it is, flat or pitched, it will

have a slight slope for draining. Typically roofs are already designed for drainage and have

gutters laid out to catch and collect water. A green roof is a great way to filter water naturally for

collecting rain water.

Figure 1

Step Two

See if the structure is capable of holding the extra weight of a green roof. Typically a

green roof will add around 25-30 lbs. of extra weight per square foot. If the structure is in a high

snowfall area or will not be able to withstand the extra weight, then extra structural beams

supports may be required. See Figure 1.

To check the structural integrity of load bearing beams, climb into the attic or crawl space

of the structure if it is a pitched roof. Inspect sheeting for rot and mold as well as large cracks

and holes. Inspect the trusses for rot, mold and cracks, next inspect the truss brackets for rust,

cracks and any loose bolts, (if applicable). If needed, replace any trusses and add heavy duty

truss brackets at the peaks and where any joints meet if planting any larger heavier plants. See

figure 2. Keep in mind not all structures can handle extra weight without adding a load bearing

wall or column. If you don’t feel comfortable inspecting the structure of your roof by yourself,

see a licensed contractor or structural engineer.

Figure 2

Step Three

Prepping the roof. Most pitched roofs have a layer of asphalt, wood or tile shingles. Flat

roofs have either asphalt and rock or a rubber membrane. All of these different types of materials

are extra added weight that will not be required and could possibly overload a structure. The

existing material will need to be tore off.

*Hint, use a square mouth shovel or a roof spade to save time.

Step Four

A barrier or box will need to be built around the edges, tall enough to keep soil and

gravel from falling off the roof. This can be built with either wood, steel or a concrete board.

Leave a half inch to an inch of gap between the edge of the roof and the bottom of the barrier for

water to drain. A wire mesh screen or chicken wire can be used to keep loose gravel in the box.

See Figure 3.

Figure 3

Step Five

Once the roof has been inspected to handle weight and the existing shingles have been

tore off, sheeting can be laid down. The type of sheeting needed will need to be a water proof

membrane or rubber roofing membrane as a root barrier to prevent damage to the roof. Before

any sheeting is laid down, a layer of insulation may be required prior to putting on the

membrane. See Figure 4.

Step Six

After the water proof membrane or rubber roofing membrane has been installed, layers

can be laid down. See Figure 4.

1. Base layer of gravel 1-2 inches thick

2. Weed liner

3. Another layer of gravel 1-2 inches thick

4. Moisture blanket (Old blankets or cardboard can be used)

5. Woodchips 1-2 inches thick

6. Enriched top soil 2-3 inches thick depending on the type of plants being grown

Step Seven

Check the structure for any bending stress marks or leaning. If the structure shows any

signs of any of these characteristics, remove the extra weight as soon as possible. More

reinforcements will be required for the structure to handle weight. See licensed contractor for

details.

Figure 4

Step Eight

Find the type of plants desired for growth, depending on the type’s environment the

structure is in. Temperate climates could be grass or even garden vegetables. Tropic climates can

be flowers, berries or even fruit plants. The types of plants will also vary the amount of soil the

roof will require for its top layer. A watering system can be added depending on rainfall and

location.

If you take these steps you can properly build your own green roof. Enjoy.

REFERENCES:

http://www.efb-greenroof.eu/verband/fachbei/fa01_englisch.html

http://www.greenroofs.com/archives/gf_aug06.htm

http://greenrooftraining.com/

http://www.thisoldhouse.com/toh/how-to/intro/0,,20473692,00.html/

https://en.wikipedia.org/wiki/Green_roof

http://www.familyhandyman.com/roof/repair/roof-removal-how-to-tear-off-roof-shingles/view-all

Figure 1

http://www.amusingplanet.com/2010_09_01_archive.html

Figure 2

https://www.etsy.com/listing/205736651/2-wood-truss-shelf-brackets-with-steel?ref=related-2

Figure 3

http://www.greenroofs.com/projects/pview.php?id=455

Figure 4

http://www.instructables.com/id/Build-a-Living-Roof-Green-Roof/step2/Theory-and-shopping/