Burnley Biodiversity Green Roof

Location:                      Burnley Campus, The University of Melbourne 500 Yarra Boulevard,                                         Richmond, Victoria

Completion date:         February 2013

Size:                                49 m2 on an existing building with heritage considerations

Description

The green roof is located above ground floor offices on a concrete roof deck with a 1 degree slope. The roof is accessible only to authorised staff or students with Working at Heights certification; however, it can be viewed from the first floor hallway window.

The Biodiversity Green Roof features:

  • Victorian grassland plant species in a shallow scoria-based growing substrate
  • a range of landscaping materials (sand, gravel, ash, rubble) and features (logs, rocks, hollow twigs, roof tiles, terracotta pots) to create habitat opportunities for birds, lizards, insects and other invertebrates
  • a small ephemeral pond and shallow creek bed, that are supplied by rainfall run-off from the roof above.

 

Introduction

The University of Melbourne has a campus in Richmond, near the Yarra River, focusing on horticultural research and education. The main building was constructed between 1946 and 1949 and is protected by a Heritage Overlay, and the entire site is listed on the Victorian Heritage Register. The northern end of the roof of the main building has been developed into a Biodiversity Green Roof as part of the larger scale Green Roofs Project, which also includes a Demonstration Roof and a Research Roof on the same building. A design team from HASSELL worked with the University to provide design solutions to assemble the roofs. Junglefy constructed the roofs. A planning consultant was hired to navigate through the planning process and clarify which permits were required.

The Biodiversity Green Roof was developed as a part of the larger Burnley Green Roofs Project to encompass demonstration, education, extension and research. The Biodiversity Green Roof provides students and visitors to the University with an example of the design and features of a non-irrigated, shallow depth green roof designed for habitat.

Design and Components

The roof has a weight loading of 150 kg/m2

Replacement of waterproofing was avoided by patch repair of existing waterproofing: the estimated cost saving was $2,000. Components include ZinCo SSM45 protection mat and high-density polyethylene (HDPE) root barrier, a ZinCo FD40 drainage layer and ZinCo Filter Sheet SF. A scoria-based growing substrate was delivered by crane in 1 m3 bulker bags, and installed to a depth of 100 mm.

A 400 mm wide unplanted perimeter zone keeps the area around the edge of the roof clear.Aluminium edge restraints separate vegetated and non-vegetated areas of the roof. Scoria aggregate was installed in the non-vegetated areas of the green roof.

The Biodiversity Roof receives run-off from two downpipes that drain the roof area above it. One is directed into the pond and ephemeral stream, the other enters a buried drain pipe that travels along the long axis of the roof. This allows lateral seepage of water into the substrate, and supports plant species with higher water needs, such as Kangaroo Grass (Themeda triandra). Drainage off the roof is achieved through two drains on the northern perimeter of the building.

There is no irrigation system on the Biodiversity Roof. It is watered infrequently by hand-held hose during hot weather or prolonged periods without rain.

The plant palette consists of Victorian perennial grasses, herbs, and one species each of an orchid and a fern. These species are typically found in grassland and woodland, and some are known sources of food and nectar for insects. Plants provide colour and interest through a significant part of the year. Tubestock (grown in the Burnley campus nursery, with a small number of plants purchased from Victorian indigenous nurseries) was planted in February 2013. The roof was hand-watered through autumn to promote establishment.

 

Herbaceous perennial herbs

 

 

Arthropodium milleflorum

Pale Vanilla Lily

Ptilotus macrocephalus

Green Pussytails

Asperula conferta

Common Woodruff

Ptilotus macrocephalus

Green Pussytails

Brachyscome basaltica

Swamp Daisy

Rumex dumosus

Wiry Dock

Brunonia australis

Blue Pincushion

Rutidosis leptorrynchoides

Button Wrinklewort

Bulbine bulbosa

Bulbine Lily

Selliera radicans

Shiny Swamp-mat

Calocephalus citreus

Lemon Beauty-heads

Senecio quadridentatus

Cotton Fireweed

Calotis anthemoides

Cut-leaf Burr-daisy

Stylidium graminifolium

Grass Trigger-plant

Chrysocephalum apiculatum

Common Everlasting

Veronica gracilis

Slender Speedwell

Cullen tenax

Emu Foot

Vittadinia cuneata

Woolly Vittadinia

Dianella revoluta

Black-anther Flax Lily

Wahlenbergia communis

Tufted Bluebell

Eryngium ovinum

Blue Devil

Grasses and grass-like forms

Eryngium vesiculosum

Prickfoot

Austrodanthonia carphoides

Short Wallaby-grass

Helichrysum rutidolepis

Pale Everlasting

Austrostipa scabra

Velvet Tussock Grass

Hypericum gramineum

Small St. John’s Wort

Chloris truncata

Windmill Grass

Leptorynchos squamatus

Scaly Buttons

Dichelachne crinita

Longhair Plumegrass

Leucochrysum albicans var. tricolor

Hoary Sunray

Lepidosperma concavum

Sword-sedge

Linum marginale

Native Flax

Lomandra filiformis

Wattle Mat-rush

Lobelia pratioides

Poison Lobelia

Themeda triandra

Kangaroo Grass

Marsilea drummondii

Common Nardoo

Orchid species

Microseris lanceolata

Yam Daisy

Microtis unifolia

Common Onion-Orchid

Pelargonium rodneyanum

Magenta Storksbill

Fern species

Podolepis jaceoides

Showy Podolepis

Cheilanthes austrotenuifolia

Green Rock Fern

 

Maintenance

Staff maintain the Biodiversity Green Roof: this takes about one hour per month. A photographic record of weed species is maintained to monitor those that germinate on the roof. Timely removal of these plants before they set seed prevents them from becoming more widespread. Plant nutrition is provided as eight to nine-month low phosphorus controlled-release fertiliser, applied at half the recommended rate.

Cost

Total: $13,930

The following details outline the indicative cost of the Biodiversity Green Roof. As it was installed as part of the larger Burnley Green Roofs Project, with works carried out simultaneously (for example, substrates for all green roofs were lifted by crane on the same day), there were economies of scale for design and installation. However, for this case study, costs are provided for a stand-alone ‘design and build’, as the scale of this roof was small and simple in relation to the overall Burnley project.

Specific costs of project components:

Preliminary costs: design, project management, etc.   
$3,000
Repairs to existing waterproofing                                           
$1,500
Protection Mat SSM 45                                                
$   250
Root barrier                                                                                      
$   100
Aluminium retaining edge (33 linear m)                            
$3,580
FD40 drainage                                                                 
$1,100
Filter Sheet SF                                                                 
$   120
Scoria-based growing substrate (10 cm depth)               
$   680
Scoria aggregate installed on non-vegetated
perimeter                                                                                          
 
$   350
Labour cost of installation including crane fees              
$1,020
Temporary fencing (required on three open sides
of the roof – 20 linear m)                                                           
 
$   630
Plant production/purchase costs                                           
$   600
Materials collection and planting                                           
$1,000
TOTAL                                                                                                               
$13,930

 

Results and Reflections

Nine months after planting the vegetation is still quite sparse, although this is likely to fill in, particularly as the grasses self-sow over time. Plants were grazed by possums living in a pair of Italian Cypress trees (Cupressus sempervirens ‘Swane’s Gold’) that were growing adjacent to the building. The trees were removed during 2013 because possum nesting and grazing caused irreparable damage to the trees’ canopies. The rooftop plants recovered well over spring.

Australian ravens and magpies visit the roof to bathe in the pond, and also bring food to consume on the roof. Spiders have colonised the tree debris, and an ant colony has moved into the rocky substrate near the end of the stream. Burnley staff members have commented on their enjoyment of the colourful grassland species planted outside the first floor window.