{"id":279,"date":"2023-02-22T18:00:07","date_gmt":"2023-02-22T23:00:07","guid":{"rendered":"http:\/\/core.loc\/development\/?page_id=279"},"modified":"2023-11-22T16:26:57","modified_gmt":"2023-11-22T21:26:57","slug":"f-9-green-roofs","status":"publish","type":"page","link":"https:\/\/water.phila.gov\/development\/stormwater-plan-review\/manual\/appendices\/f-design-guidance-checklists\/f-9-green-roofs\/","title":{"rendered":"F.9 Green Roofs"},"content":{"rendered":"\n

F.9.1 Green Roof Plan Standards<\/h4>\n\n\n\n
    \n
  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]<\/li>\n\n\n\n
  2. Verify that the plans include an appropriate cross-sectional detail for the green roof. [Section 2.3.1]<\/li>\n\n\n\n
  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\u20117]<\/li>\n<\/ol>\n\n\n\n

    F.9.2 Green Roof Design Standards<\/h4>\n\n\n\n
      \n
    1. Verify that runoff from impervious roof area onto the green roof is dispersed evenly across the green roof surface and passes through the growing medium either by sheet flow or a level spreading device. [Section 4.3.3, 1]<\/li>\n\n\n\n
    2. Verify that the flow path of runoff across the green roof surface is greater than or equal to the contributing DCIA length. [Section 4.3.3, 2]<\/li>\n\n\n\n
    3. Verify that structural loading is considered for the green roof design, and that the green roof design is coordinated with a licensed structural engineer for both new building construction and retrofits to existing structures. [Section 4.3.3, 3a]<\/li>\n\n\n\n
    4. If runoff estimation calculations are required, verify that the correct curve number for the proposed green roof is used in the calculations. Refer to Table 3.4\u20112 of the Manual. [Section 4.3.3, 4a]<\/li>\n\n\n\n
    5. If flow routing is required, verify that the rational coefficient used is 0.40. [Section 4.3.3, 4b]<\/li>\n\n\n\n
    6. If flow routing is required, verify that the time of concentration used is six minutes. [Section 4.3.3, 4c]<\/li>\n\n\n\n
    7. Verify that the total amount of impervious surfaces within the designated boundary of the green roof footprint does not exceed 1\/3 of the combined area. [Section 4.3.3, 5]<\/li>\n\n\n\n
    8. If runoff is conveyed via piping, verify that a distribution piping manifold embedded in a gravel strip, along with an appropriate detail, is provided on the plans to dissipate energy and promote uniform flow. [Section 4.3.3, 7]<\/li>\n\n\n\n
    9. For green roofs that receive direct (1:1) rainfall only, verify the following:\n
        \n
      1. The minimum allowable thickness of the green roof growing medium is three inches. This can include both an upper finer-grained medium and a basal foundation growth media (lightweight drainage aggregate). The minimum allowable thickness of the foundation growth media is one inch. [Section 4.3.3, 9a]<\/li>\n\n\n\n
      2. Green roofs that meet minimum growing medium thickness requirements are permitted a DCIA reduction equal to the entire area of the green roof. [Section 4.3.3, 9b]<\/li>\n<\/ol>\n<\/li>\n\n\n\n
      3. For green roofs that receive runoff from contributing impervious roof catchments, verify the following:\n
          \n
        1. Impervious roof areas that direct runoff onto the green roof cannot exceed 50% of the green roof area, which is equivalent to a maximum hydraulic impervious runoff loading ratio of 0.5:1. [Section 4.3.3, 10a]<\/li>\n\n\n\n
        2. The minimum thickness of the green roof growing medium must be calculated as follows, where the \u201cimpervious roof area to green roof area\u201d ratio is less than or equal to 0.50: [Section 4.3.3, 10b] Minimum thickness (in inches) of green roof growing medium<\/span>  = <\/span> 3 inches<\/span>  + <\/span> [ <\/span> 3<\/span>  * <\/span> ( <\/span>Impervious roof area \/ <\/span>Green roof area<\/span> )<\/span>  ]<\/span><\/span><\/li>\n\n\n\n
        3. Green roofs that meet minimum growing medium thickness requirements are permitted a DCIA reduction equal to the entire area of the green roof. Impervious roof areas that drain to these green roofs can be also considered as disconnected impervious cover, and, thus, included in the green roof\u2019s DCIA reduction. [Section 4.3.3, 10c]<\/li>\n\n\n\n
        4. In areas that will receive tributary discharge, verify that the plans include specifications that demonstrate that the drainage layer is not a high-transmissivity drainage layer, defined as a layer with a transmissivity of 0.005 m2<\/sup>\/s or greater (ASTM D4716). In general, this will exclude peg-style or egg-carton-style geosynthetic sheets. High-transmissivity drainage layers will allow runoff to effectively flow under the green roof, minimizing contact with medium and plant roots. Typical granular aggregate, or coarse granular green roof medium, with a grain-size distribution complying with ASTM gradation No. 7 will satisfy the requirement, as will also a variety of mats and composite drainage layer assemblies. [Section 4.3.3, 10d]<\/li>\n\n\n\n
        5. Verify that any deck built atop a green roof that does not allow for sheet flow runoff is slotted, and that the minimum thickness of growing medium required for the green roof is maintained under the entire extent of the deck. [Section 4.3.3, 10e]<\/li>\n<\/ol>\n<\/li>\n\n\n\n
        6. Verify that the plans indicate that the saturated permeability of the growing medium, in its compacted state [ASTM E2399], is not less than six inches per hour. [Section 4.3.3, 11]<\/li>\n\n\n\n
        7. Verify that a drainage layer is provided and that it prevents ponding of runoff in the growing medium during the ten-minute maximum rainfall rate associated with the one-year, 24-hour storm event. [Section 4.3.3, 13]<\/li>\n\n\n\n
        8. Verify that the contributing area of rooftop to each disconnected discharge point is equal to, or less than, 500 square feet. [Section 4.3.3, 15]<\/li>\n\n\n\n
        9. Verify that details are provided on the plans that demonstrate that all drains and scuppers are covered and protected by an enclosure, typically a square or round chamber with a locking lid. These chambers are designed to prevent clogging of the drains by debris. [Section 4.3.3, 17]<\/li>\n\n\n\n
        10. Verify that the roof drainage system and the remainder of the site drainage system safely convey roof runoff to the storm sewer, combined sewer, or receiving water. [Section 4.3.3, 18]<\/li>\n\n\n\n
        11. Verify that the green roof is designed to allow for safe access and working conditions for green roof inspection and maintenance personnel. This access must be a permanent feature of the building, such as a pilot house, roof hatch, or exterior stairs to the green roof. Retractable, unsecured ladders should not be required for routine maintenance and inspections. The design may include other permanent personal safety measures. For green roofs, designers must specifically assess applicability to Occupational Safety and Health Administration (OSHA) Fall Protection Safety Standards and the American National Standards Institute (ANSI) and American Society of Safety Engineers (ASSE) consensus-based fall protection standards. [Section 4.3.3, 20]<\/li>\n<\/ol>\n\n\n\n

          F.9.3 Green Roof Material Standards<\/h4>\n\n\n\n
            \n
          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]\n
              \n
            1. Moisture content at maximum water holding capacity (ASTM E2399 or FLL): 40% to 60% (vol)<\/li>\n\n\n\n
            2. Porosity at maximum water holding capacity (ASTM E2399 or FLL): 10% to 15%<\/li>\n\n\n\n
            3. Density at maximum water holding capacity (ASTM E2399 or FLL): \u2264 85 lb\/ft3<\/li>\n\n\n\n
            4. Total organic matter (MSA): 6% to 10% (dry weight)<\/li>\n\n\n\n
            5. pH (MSA): 6.5 to 7.8<\/li>\n\n\n\n
            6. Soluble salts (DPTA saturated media extraction): \u2264 2 mmhos\/cm<\/li>\n\n\n\n
            7. Water permeability (ASTM E2399 or FLL): 0.25 in\/min to 1.25 in\/min<\/li>\n\n\n\n
            8. Grain-size distribution consisting of \u2264 4.5% passing for clay (0.002 mm) and 5% to 15% passing for silt (0.05 mm)<\/li>\n\n\n\n
            9. The nutrients must be initially incorporated in the formulation of a suitable mix for the support of the specified plant materials.<\/li>\n\n\n\n
            10. The medium must withstand freeze\/thaw cycles.<\/li>\n<\/ol>\n<\/li>\n\n\n\n
            11. 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]\n
                \n
              1. Density at maximum water capacity (ASTM E2399-05): \u2264 65 lbs\/ft3<\/sup><\/li>\n\n\n\n
              2. Maximum water holding capacity: 15% to 25%<\/li>\n\n\n\n
              3. Water permeability (ASTM E2396-05): \u2265 25 in\/min<\/li>\n\n\n\n
              4. Total organic matter by loss on ignition (ASTM F1647): \u2264 1%<\/li>\n\n\n\n
              5. Porosity (ASTM C29): 20% to 65%<\/li>\n\n\n\n
              6. Grain-size distribution (ASTM C136) consisting of the following gradations:\n
                  \n
                1. Pct. Passing US#18 sieve (1.0 mm): \u2264 5%<\/li>\n\n\n\n
                2. Pct. Passing \u00bc-inch sieve: \u2264 30%<\/li>\n\n\n\n
                3. Pct. Passing 3\/8-inch sieve (9.5 mm): \u2265 75%<\/li>\n\n\n\n
                4. Pct. Passing \u00bd-inch sieve (12 mm): 100%<\/li>\n<\/ol>\n<\/li>\n<\/ol>\n<\/li>\n\n\n\n
                5. 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]\n
                    \n
                  1. Grab Tensile Strength (ASTM-D4632): \u2264 120 lbs<\/li>\n\n\n\n
                  2. Mullen Burst Strength (ASTM-D3786): \u2265 225 psi<\/li>\n\n\n\n
                  3. Flow Rate (ASTM-D4491): \u2265 95 gal\/min\/ft2<\/sup><\/li>\n\n\n\n
                  4. UV Resistance after 500 hrs (ASTM-D4355): \u2265 70%<\/li>\n\n\n\n
                  5. Heat-set or heat-calendared fabrics are not permitted<\/li>\n<\/ol>\n<\/li>\n\n\n\n
                  6. 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]\n
                      \n
                    1. Abrasion resistance (ASTM-C131-96): \u2264 25% loss<\/li>\n\n\n\n
                    2. Soundness (ASTM-C88): \u2264 5% loss<\/li>\n\n\n\n
                    3. Porosity (ASTM-C29): \u2265 25%<\/li>\n\n\n\n
                    4. Percent of particles passing 1\/2-inch sieve (ASTM-C136): \u2265 75%<\/li>\n\n\n\n
                    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.<\/li>\n<\/ol>\n<\/li>\n\n\n\n
                    6. 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]<\/li>\n\n\n\n
                    7. 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]<\/li>\n\n\n\n
                    8. Verify that roofing membranes meet all building code requirements and guidelines of the City of Philadelphia. [Section 4.3.4, 6d]<\/li>\n\n\n\n
                    9. 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<\/a> for plant lists. [Section 4.3.4, 7]<\/li>\n\n\n\n
                    10. Verify that sedum sarmentosum, also known as star sedum, gold moss, stringy stonecrop, or graveyard moss, is not proposed. [Section 4.3.4, 10]<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

                      F.9.1 Green Roof Plan Standards F.9.2 Green Roof Design Standards F.9.3 Green Roof Material Standards<\/p>\n","protected":false},"author":3,"featured_media":0,"parent":898,"menu_order":9,"comment_status":"closed","ping_status":"closed","template":"page-manual.php","meta":{"custom_css":"","custom_js":"","dp_submitted":"0","dp_notify":"0","dp_created":"","version":"","effective":"","short-page-title":"","pwd_rlv_phrase_match":"f 9 green roofs | f 9 green roofs | f 9 1 green roof plan standards | 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 | verify that the plans include an appropriate cross sectional detail for the green roof section 2 3 1 | 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 | verify that runoff from impervious roof area onto the green roof is dispersed evenly across the green roof surface and passes through the growing medium either by sheet flow or a level spreading device section 4 3 3 1 | verify that the flow path of runoff across the green roof surface is greater than or equal to the contributing dcia length section 4 3 3 2 | verify that structural loading is considered for the green roof design and that the green roof design is coordinated with a licensed structural engineer for both new building construction and retrofits to existing structures section 4 3 3 3a | if runoff estimation calculations are required verify that the correct curve number for the proposed green roof is used in the calculations refer to table 3 4 2 of the manual section 4 3 3 4a | if flow routing is required verify that the rational coefficient used is 0 40 section 4 3 3 4b | if flow routing is required verify that the time of concentration used is six minutes section 4 3 3 4c | verify that the total amount of impervious surfaces within the designated boundary of the green roof footprint does not exceed 1 3 of the combined area section 4 3 3 5 | if runoff is conveyed via piping verify that a distribution piping manifold embedded in a gravel strip along with an appropriate detail is provided on the plans to dissipate energy and promote uniform flow section 4 3 3 7 | for green roofs that receive direct 1 1 rainfall only verify the following | the minimum allowable thickness of the green roof growing medium is three inches this can include both an upper finer grained medium and a basal foundation growth media lightweight drainage aggregate the minimum allowable thickness of the foundation growth media is one inch section 4 3 3 9a | green roofs that meet minimum growing medium thickness requirements are permitted a dcia reduction equal to the entire area of the green roof section 4 3 3 9b | for green roofs that receive runoff from contributing impervious roof catchments verify the following | impervious roof areas that direct runoff onto the green roof cannot exceed 50 of the green roof area which is equivalent to a maximum hydraulic impervious runoff loading ratio of 0 5 1 section 4 3 3 10a | the minimum thickness of the green roof growing medium must be calculated as follows where the impervious roof area to green roof area ratio is less than or equal to 0 50 section 4 3 3 10b minimum thickness in inches of green roof growing medium 3 inches 3 impervious roof area green roof area | green roofs that meet minimum growing medium thickness requirements are permitted a dcia reduction equal to the entire area of the green roof impervious roof areas that drain to these green roofs can be also considered as disconnected impervious cover and thus included in the green roofs dcia reduction section 4 3 3 10c | in areas that will receive tributary discharge verify that the plans include specifications that demonstrate that the drainage layer is not a high transmissivity drainage layer defined as a layer with a transmissivity of 0 005 m 2 s or greater astm d4716 in general this will exclude peg style or egg carton style geosynthetic sheets high transmissivity drainage layers will allow runoff to effectively flow under the green roof minimizing contact with medium and plant roots typical granular aggregate or coarse granular green roof medium with a grain size distribution complying with astm gradation no 7 will satisfy the requirement as will also a variety of mats and composite drainage layer assemblies section 4 3 3 10d | verify that any deck built atop a green roof that does not allow for sheet flow runoff is slotted and that the minimum thickness of growing medium required for the green roof is maintained under the entire extent of the deck section 4 3 3 10e | verify that the plans indicate that the saturated permeability of the growing medium in its compacted state astm e2399 is not less than six inches per hour section 4 3 3 11 | verify that a drainage layer is provided and that it prevents ponding of runoff in the growing medium during the ten minute maximum rainfall rate associated with the one year 24 hour storm event section 4 3 3 13 | verify that the contributing area of rooftop to each disconnected discharge point is equal to or less than 500 square feet section 4 3 3 15 | verify that details are provided on the plans that demonstrate that all drains and scuppers are covered and protected by an enclosure typically a square or round chamber with a locking lid these chambers are designed to prevent clogging of the drains by debris section 4 3 3 17 | verify that the roof drainage system and the remainder of the site drainage system safely convey roof runoff to the storm sewer combined sewer or receiving water section 4 3 3 18 | verify that the green roof is designed to allow for safe access and working conditions for green roof inspection and maintenance personnel this access must be a permanent feature of the building such as a pilot house roof hatch or exterior stairs to the green roof retractable unsecured ladders should not be required for routine maintenance and inspections the design may include other permanent personal safety measures for green roofs designers must specifically assess applicability to occupational safety and health administration osha fall protection safety standards and the american national standards institute ansi and american society of safety engineers asse consensus based fall protection standards section 4 3 3 20 | f 9 3 green roof material standards | 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 | moisture content at maximum water holding capacity astm e2399 or fll 40 to 60 vol | porosity at maximum water holding capacity astm e2399 or fll 10 to 15 | density at maximum water holding capacity astm e2399 or fll 85 lb ft3 | total organic matter msa 6 to 10 dry weight | ph msa 6 5 to 7 8 | soluble salts dpta saturated media extraction 2 mmhos cm | water permeability astm e2399 or fll 0 25 in min to 1 25 in min | grain size distribution consisting of 4 5 passing for clay 0 002 mm and 5 to 15 passing for silt 0 05 mm | the nutrients must be initially incorporated in the formulation of a suitable mix for the support of the specified plant materials | the medium must withstand freeze thaw cycles | 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 | density at maximum water capacity astm e2399 05 65 lbs ft 3 | maximum water holding capacity 15 to 25 | water permeability astm e2396 05 25 in min | total organic matter by loss on ignition astm f1647 1 | porosity astm c29 20 to 65 | grain size distribution astm c136 consisting of the following gradations | pct passing us 18 sieve 1 0 mm 5 | pct passing \u00bc inch sieve 30 | pct passing 3 8 inch sieve 9 5 mm 75 | pct passing \u00bd inch sieve 12 mm 100 | 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 | grab tensile strength astm d4632 120 lbs | mullen burst strength astm d3786 225 psi | flow rate astm d4491 95 gal min ft 2 | uv resistance after 500 hrs astm d4355 70 | heat set or heat calendared fabrics are not permitted | 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 | abrasion resistance astm c131 96 25 loss | soundness astm c88 5 loss | porosity astm c29 25 | percent of particles passing 1 2 inch sieve astm c136 75 | the minimum thickness of the granular layer must be two inches the granular layer may be installed in conjunction with a synthetic reservoir sheet | 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 | 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 | verify that roofing membranes meet all building code requirements and guidelines of the city of philadelphia section 4 3 4 6d | 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 | verify that sedum sarmentosum also known as star sedum gold moss stringy stonecrop or graveyard moss is not proposed section 4 3 4 10","pwd_rlv_wordcount":"1424"},"section":[],"class_list":["post-279","page","type-page","status-publish","hentry","wpautop"],"acf":[],"parsely":{"version":"1.1.0","canonical_url":"https:\/\/phila.gov\/development\/stormwater-plan-review\/manual\/appendices\/f-design-guidance-checklists\/f-9-green-roofs\/","smart_links":{"inbound":0,"outbound":0},"traffic_boost_suggestions_count":0,"meta":{"@context":"https:\/\/schema.org","@type":"WebPage","headline":"F.9 Green Roofs","url":"http:\/\/water.phila.gov\/development\/stormwater-plan-review\/manual\/appendices\/f-design-guidance-checklists\/f-9-green-roofs\/","mainEntityOfPage":{"@type":"WebPage","@id":"http:\/\/water.phila.gov\/development\/stormwater-plan-review\/manual\/appendices\/f-design-guidance-checklists\/f-9-green-roofs\/"},"thumbnailUrl":"","image":{"@type":"ImageObject","url":""},"articleSection":"Uncategorized","author":[{"@type":"Person","name":"Lauren Sell"}],"creator":["Lauren Sell"],"publisher":{"@type":"Organization","name":"Development Services","logo":""},"keywords":[],"dateCreated":"2023-02-22T23:00:07Z","datePublished":"2023-02-22T23:00:07Z","dateModified":"2023-11-22T21:26:57Z"},"rendered":"