Appendices

F.9 Green Roofs

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F.9.1 Green Roof Plan Standards

  1. Verify that the plans include an appropriate sequence of construction that is specific to the construction of the green roof. Refer to Section 4.3.5 for guidance. [Section 2.3.1]
  2. Verify that the plans include an appropriate cross-sectional detail for the green roof. [Section 2.3.1]
  3. Verify that a roof drainage plan is provided and that the roof drainage is consistent with the green roof design. [Appendix E, Table E‑7]

F.9.2 Green Roof Design Standards

F.9.3 Green Roof Material Standards

  1. Verify that the green roof growing medium is specified on the plans to be a lightweight mineral material with a minimum of organic material that meets the following specifications: [Section 4.3.4, 2]
    1. Moisture content at maximum water holding capacity (ASTM E2399 or FLL): 40% to 60% (vol)
    2. Porosity at maximum water holding capacity (ASTM E2399 or FLL): 10% to 15%
    3. Density at maximum water holding capacity (ASTM E2399 or FLL): ≤ 85 lb/ft3
    4. Total organic matter (MSA): 6% to 10% (dry weight)
    5. pH (MSA): 6.5 to 7.8
    6. Soluble salts (DPTA saturated media extraction): ≤ 2 mmhos/cm
    7. Water permeability (ASTM E2399 or FLL): 0.25 in/min to 1.25 in/min
    8. Grain-size distribution consisting of ≤ 4.5% passing for clay (0.002 mm) and 5% to 15% passing for silt (0.05 mm)
    9. The nutrients must be initially incorporated in the formulation of a suitable mix for the support of the specified plant materials.
    10. The medium must withstand freeze/thaw cycles.
  2. Verify that the foundation growth media (lightweight drainage aggregate) is specified on the plans to be composed of blended media that meets the following specifications: [Section 4.3.4, 3]
    1. Density at maximum water capacity (ASTM E2399-05): ≤ 65 lbs/ft3
    2. Maximum water holding capacity: 15% to 25%
    3. Water permeability (ASTM E2396-05): ≥ 25 in/min
    4. Total organic matter by loss on ignition (ASTM F1647): ≤ 1%
    5. Porosity (ASTM C29): 20% to 65%
    6. Grain-size distribution (ASTM C136) consisting of the following gradations:
      1. Pct. Passing US#18 sieve (1.0 mm): ≤ 5%
      2. Pct. Passing ¼-inch sieve: ≤ 30%
      3. Pct. Passing 3/8-inch sieve (9.5 mm): ≥ 75%
      4. Pct. Passing ½-inch sieve (12 mm): 100%
  3. Verify that geotextile is specified on the plans to consist of polypropylene fibers and to meet the following specifications (AASHTO Class 1 or Class 2 geotextile is recommended): [Section 4.3.4, 4]
    1. Grab Tensile Strength (ASTM-D4632): ≤ 120 lbs
    2. Mullen Burst Strength (ASTM-D3786): ≥ 225 psi
    3. Flow Rate (ASTM-D4491): ≥ 95 gal/min/ft2
    4. UV Resistance after 500 hrs (ASTM-D4355): ≥ 70%
    5. Heat-set or heat-calendared fabrics are not permitted
  4. For vegetated cover assemblies with an overall thickness of five inches or greater, verify that the drainage layer is specified on the plans to meet the following specifications: [Section 4.3.4, 5b]
    1. Abrasion resistance (ASTM-C131-96): ≤ 25% loss
    2. Soundness (ASTM-C88): ≤ 5% loss
    3. Porosity (ASTM-C29): ≥ 25%
    4. Percent of particles passing 1/2-inch sieve (ASTM-C136): ≥ 75%
    5. The minimum thickness of the granular layer must be two inches. The granular layer may be installed in conjunction with a synthetic reservoir sheet.
  5. Verify that all waterproof membranes meet appropriate ASTM specifications. PVC membranes must meet ASTM D4434 requirements, EPDM membranes must meet ASTM D4637 requirements, and TPO membranes must meet ASTM D6878 requirements. [Section 4.3.4, 6b]
  6. Verify that all waterproofing membranes are fully waterproof with properly sealed seams, corners, and protrusions to prevent any intrusion of standing water above the membrane. [Section 4.3.4, 6c]
  7. Verify that roofing membranes meet all building code requirements and guidelines of the City of Philadelphia. [Section 4.3.4, 6d]
  8. Verify that the proposed green roof plantings are indicated on the plans and that the proposed plantings and are non-invasive. Refer to Appendix I for plant lists. [Section 4.3.4, 7]
  9. Verify that sedum sarmentosum, also known as star sedum, gold moss, stringy stonecrop, or graveyard moss, is not proposed. [Section 4.3.4, 10]
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