ASTM E2397/E2397M-19

Standard Practice for Determination of Dead Loads and Live Loads Associated with Vegetative (Green) Roof Systems

SIGNIFICANCE AND USE
5.1 This practice addresses performance characteristics for vegetative (green) roof systems with respect to the dead load and transient water load of the entire vegetative (green) roof system.  
5.2 Determining these performance characteristics of vegetative (green) roof systems provides information to facilitate the assessment of related engineering aspects of the facility. Such aspects may include structural design requirements, mechanical engineering and thermal design requirements, and fire and life safety requirements.  
5.3 Determining these performance characteristics of vegetative (green) roof systems provides information to facilitate assessment of the performance of one vegetative (green) roof system relative to another.
SCOPE
1.1 This practice covers a standardized procedure for predicting the system weight of a vegetative (green) roof system.  
1.2 The practice addresses the loads associated with vegetative (green) roof systems. Components that are typically encountered in vegetative (green) roof systems include: membranes, non-absorptive plastic sheet components, metallic layers, fabrics, geocomposite drain layers, synthetic reinforcing layers, cover/recover boards, insulation materials, growth media, granular drainage media, and plant materials.  
1.3 This practice also addresses the weight of the vegetative (green) roof system under two conditions: (1) weight under drained conditions after new water additions by rainfall or irrigation have ceased (this includes the weight of retained water and captured water), and (2) weight when rainfall or irrigation is actively occurring and the drain layer is completely filled with water. The first condition is considered the dead load of the vegetative (green) roof system. The difference in weight between the first and second conditions, approximated by the weight of transient water in the drain layer, is considered a live load.  
1.4 This practice does not address point or line loads associated with architectural elements that are not essential components of a particular vegetative (green) roof system. These architectural elements may include pavement, walls, and masonry, and so forth.  
1.5 This practice does not address live loads associated with construction activities.  
1.6 This practice does not address loads associated with snow or wind.  
1.7 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.  
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and to determine the applicability of regulatory limitations prior to use.  
1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Jan-2019
• ICS: 65.020.20 - Plant growing
• ICS: 91.060.20 - Roofs
• Technical Committee: D08 - Roofing and Waterproofing
• Drafting Committee: D08.24 - Sustainability

Relations

• Replaces: ASTM E2397/E2397M-15 - Standard Practice for Determination of Dead Loads and Live Loads Associated with Vegetative (Green) Roof Systems
• Effective Date: 01-Feb-2019
• Refers: ASTM E2398/E2398M-19 - Standard Test Method for Water Capture and Media Retention of Geocomposite Drain Layers for Vegetative (Green) Roof Systems
• Effective Date: 01-Feb-2019
• Refers: ASTM E2399/E2399M-19 - Standard Test Method for Maximum Media Density for Dead Load Analysis of Vegetative (Green) Roof Systems
• Effective Date: 01-Feb-2019
• Refers: ASTM E2396/E2396M-19 - Standard Test Method for Saturated Water Permeability of Granular Drainage Media [Falling-Head Method] for Vegetative (Green) Roof Systems
• Effective Date: 01-Feb-2019
• Refers: ASTM E2114-17 - Standard Terminology for Sustainability Relative to the Performance of Buildings
• Effective Date: 01-Feb-2017
• Refers: ASTM E2398/E2398M-15a - Standard Test Method for Water Capture and Media Retention of Geocomposite Drain Layers for Vegetative (Green) Roof Systems
• Effective Date: 01-Nov-2015
• Refers: ASTM E2396/E2396M-15 - Standard Test Method for Saturated Water Permeability of Granular Drainage Media [Falling-Head Method] for Vegetative (Green) Roof Systems
• Effective Date: 01-Jun-2015
• Refers: ASTM E2398/E2398M-15 - Standard Test Method for Water Capture and Media Retention of Geocomposite Drain Layers for Vegetative (Green) Roof Systems
• Effective Date: 01-Jun-2015
• Refers: ASTM E2399/E2399M-15 - Standard Test Method for Maximum Media Density for Dead Load Analysis of Vegetative (Green) Roof Systems
• Effective Date: 01-Jun-2015
• Refers: ASTM E631-15 - Standard Terminology of Building Constructions
• Effective Date: 01-Mar-2015
• Refers: ASTM E631-14 - Standard Terminology of Building Constructions
• Effective Date: 01-Nov-2014
• Refers: ASTM E11-13 - Standard Specification for Woven Wire Test Sieve Cloth and Test Sieves
• Effective Date: 01-Oct-2013
• Refers: ASTM E11-09e1 - Standard Specification for Woven Wire Test Sieve Cloth and Test Sieves
• Effective Date: 01-May-2009
• Refers: ASTM E2114-08 - Standard Terminology for Sustainability Relative to the Performance of Buildings
• Effective Date: 01-Nov-2008
• Refers: ASTM E2114-06a - Standard Terminology for Sustainability Relative to the Performance of Buildings
• Effective Date: 01-Dec-2006

Overview

ASTM E2397/E2397M-19 is the standard practice developed by ASTM International for the determination of dead loads and live loads associated with vegetative (green) roof systems. This standard provides a systematic approach to predicting and measuring the weights relevant to the components and water-retention characteristics of green roofing systems. The procedure outlined is vital for evaluating the structural, mechanical, thermal, and safety requirements essential for the successful implementation and comparison of vegetative roof designs.

Keywords: green roof load, vegetative roof dead load, live load, green roof system, water retention, ASTM E2397/E2397M-19

Key Topics

• Dead Loads: The standard defines dead load as the weight of the vegetative roof system under drained conditions, including all retained and captured water but after rainfall or irrigation have ceased.
• Live (Transient) Loads: Live load refers to the additional weight added when rainfall or irrigation is actively occurring and the drain layer is completely filled with water. The difference in weight between this state and the drained state characterizes the live load.
• Component Weight Assessment: The practice details procedures to measure the weight of various typical green roof components, such as:
  • Waterproof membranes
  • Non-absorptive plastic sheets
  • Metallic layers and fabrics
  • Geocomposite drain layers
  • Synthetic reinforcing
  • Growth media and granular drainage media
  • Plant materials
• Water Retention Analysis: The standard addresses methods for determining the amount of water captured and retained by different system layers, making it possible to estimate the overall load introduced by water under different conditions.
• Reporting & Units: Both SI and inch-pound units are accepted, but should be used independently to avoid non-conformance.

Applications

• Structural Design: The standard's procedures assist structural engineers in accurately estimating roof loads, essential for verifying compliance with building codes and ensuring safety and reliability.
• Mechanical and Thermal System Planning: By determining the load and water retention of green roofs, mechanical and thermal designs can be optimized for energy efficiency and durability.
• Fire and Life Safety Assessment: Knowing exact loads, especially in saturated conditions, informs safety planning and emergency protocols.
• Comparative Performance Evaluation: Facilities managers, architects, and specifiers can leverage this standard to compare different vegetative roofing systems based on standardized load criteria.
• Sustainability Planning: Understanding water retention supports sustainability goals and helps tailor green roof designs for stormwater management and ecological performance.

Related Standards

Several ASTM standards are referenced or commonly used in conjunction with ASTM E2397/E2397M-19, including:

• ASTM E11: Specification for woven wire test sieve cloth and test sieves
• ASTM E631: Terminology of building constructions
• ASTM E2114: Terminology for sustainability related to building performance
• ASTM E2396/E2396M: Test method for saturated water permeability of granular drainage media for green roofs
• ASTM E2398/E2398M: Test method for water capture and media retention of geocomposite drain layers
• ASTM E2399/E2399M: Test method for maximum media density for dead load analysis of green roof systems

ASTM E2397/E2397M-19 is an integral component within the suite of standards supporting safe, efficient, and sustainable vegetative roof system implementation, ensuring accurate and consistent calculation of both dead and live loads induced by green roof construction and maintenance.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E2397/E2397M − 19
Standard Practice for
Determination of Dead Loads and Live Loads Associated
with Vegetative (Green) Roof Systems
ThisstandardisissuedunderthefixeddesignationE2397/E2397M;thenumberimmediatelyfollowingthedesignationindicatestheyear
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope system shall be used independently of the other. Combining
values from the two systems may result in non-conformance
1.1 This practice covers a standardized procedure for pre-
with the standard.
dicting the system weight of a vegetative (green) roof system.
1.8 This standard does not purport to address all of the
1.2 The practice addresses the loads associated with vegeta-
safety concerns, if any, associated with its use. It is the
tive (green) roof systems. Components that are typically
responsibility of the user of this standard to establish appro-
encountered in vegetative (green) roof systems include:
priate safety, health, and environmental practices and to
membranes, non-absorptive plastic sheet components, metallic
determine the applicability of regulatory limitations prior to
layers, fabrics, geocomposite drain layers, synthetic reinforc-
use.
ing layers, cover/recover boards, insulation materials, growth
1.9 This international standard was developed in accor-
media, granular drainage media, and plant materials.
dance with internationally recognized principles on standard-
1.3 This practice also addresses the weight of the vegetative
ization established in the Decision on Principles for the
(green) roof system under two conditions: (1) weight under
Development of International Standards, Guides and Recom-
drained conditions after new water additions by rainfall or
mendations issued by the World Trade Organization Technical
irrigation have ceased (this includes the weight of retained
Barriers to Trade (TBT) Committee.
water and captured water), and (2) weight when rainfall or
irrigationisactivelyoccurringandthedrainlayeriscompletely 2. Referenced Documents
filledwithwater.Thefirstconditionisconsideredthedeadload 2
2.1 ASTM Standards:
of the vegetative (green) roof system. The difference in weight
E11 Specification for Woven Wire Test Sieve Cloth and Test
between the first and second conditions, approximated by the
Sieves
weight of transient water in the drain layer, is considered a live
E631 Terminology of Building Constructions
load.
E2114 Terminology for Sustainability Relative to the Perfor-
1.4 This practice does not address point or line loads mance of Buildings
E2396/E2396M Test Method for SaturatedWater Permeabil-
associated with architectural elements that are not essential
components of a particular vegetative (green) roof system. ity of Granular Drainage Media [Falling-Head Method]
for Vegetative (Green) Roof Systems
These architectural elements may include pavement, walls, and
masonry, and so forth. E2398/E2398M Test Method for Water Capture and Media
Retention of Geocomposite Drain Layers for Vegetative
1.5 This practice does not address live loads associated with
(Green) Roof Systems
construction activities.
E2399/E2399M Test Method for Maximum Media Density
1.6 This practice does not address loads associated with
for Dead Load Analysis of Vegetative (Green) Roof
snow or wind.
Systems
1.7 The values stated in either SI units or inch-pound units
3. Terminology
are to be regarded separately as standard. The values stated in
each system may not be exact equivalents; therefore, each
3.1 Definitions:
3.1.1 For terms related to building construction, refer to
Terminology E631.
This Practice is under the jurisdiction of ASTM Committee D08 on Roofing
and Waterproofing and is the direct responsibility of Subcommittee D08.24 on
Sustainability. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Feb. 1, 2019. Published March 2019. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2005. Last published in 2015 as E2397/E2397M – 15. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
E2397_E2397M-19. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2397/E2397M − 19
3.1.2 For terms related to sustainability relative to the a vegetative (green) roof system, or in one of its components,
performance of buildings, refer to Terminology E2114. after new additions by rainfall or artificial irrigation have
3.2 Definitions of Terms Specific to This Standard: ceased. Neglecting the effects of capillary rise, evaporation,
3.2.1 captured water, n—the quantity of water that is re- and plant transpiration all of this water would eventually
producerunoff.However,inpracticemostofthiswaterwillnot
tained in the drain layer of a vegetative (green) roof system
after new water additions have ceased and that cannot escape become runoff but will be lost to evaporation and the plant-
mediated processes of transpiration. This procedure describes
the roof except through evaporation or plant transpiration.
standardized methods for estimating the quantity of water
3.2.1.1 Discussion—Water capture is a design technique for
retained in a vegetative (green) roof system.
enhancing the water holding properties of a vegetative (green)
roof system. Water may be captured using a number of
3.2.7 roof system, n—see roofing system.
techniques, including reservoirs built into a geocomposite
3.2.8 roofing system, n—assembly of interacting compo-
drain layer, trays, and restricting drainage in order to hold
nents designed to weatherproof, and sometimes to insulate, the
water within the drain layer. In some vegetative (green) roof
roof surface of a building. E631
systems a granular course at the bottom of the vegetative
3.2.8.1 Discussion—This term includes all components
(green) roof system provides both drainage and water capture
abovetheroofdeckthatarenotpartoftheoverlyingvegetative
functions. In this case the captured water applies only to the
(green) roof system. In practice this usually means the water-
thickness of the granular course for which drainage is re-
proofing membrane and all materials below the waterproofing
stricted. A method for determining the captured water associ-
membrane, down to the structural deck. It may include
ated with geocomposites based on the unit water capture
structural materials such as cover/recover board, insulation,
volume is provided in Test Method E2398/E2398M. The
protective layers, fire-suppressing materials, and waterproofing
quantity of captured water will depend on whether or not the
materials.The weight of these components (assumed dry) must
upper surface of the geocomposite drain layer is in-filled with
be obtained from the manufacturer of the roofing system.
granular media.
3.2.9 transient water, n—the quantity of water that is re-
3.2.2 geocompositedrainlayer,n—asyntheticsheet,mat,or
quired to completely fill the drain layer of a vegetative (green)
panel that is specifically designed to convey water horizontally
roof system, less the quantity of captured water.
toward the roof deck drains, gutters, or scuppers.
3.2.9.1 Discussion—Transient water fills the open space,
3.2.2.1 Discussion—Geocomposite drain layers include ab-
including pore spaces. This water can only be held for a period
sorptive drain mats whose principle function is drainage, but
of minutes and drains immediately when rainfall additions end.
which will also contribute to water retention (see retained
This moisture contributes to the live load of the vegetative
water). Some geocomposite drain layers may incorporate
(green) roof system.
reservoirs on their upper surfaces that will capture water (see
captured water).
4. Summary of Practice
3.2.3 maximum media density, n—the density of a mixed
4.1 This practice describes a systematic procedure for esti-
media material determined after it has been subjected to a
matingthedeadloadandtransientwaterliveloadofvegetative
specific amount of compaction and hydrated by immersion to
(green) roof systems using information about the vegetative
simulate prolonged exposure to both foot traffic and rainfall.
(green) roof components that are available from laboratory
3.2.3.1 Discussion—The maximum media density applies to
analysis.
media in a drained condition. The measurement of the maxi-
5. Significance and Use
mum media density is provided in Test Method E2399/
E2399M.
5.1 This practice addresses performance characteristics for
vegetative (green) roof systems with respect to the dead load
3.2.4 maximum media water retention—the quantity of wa-
ter held in a media layer at the maximum media density, and transient water load of the entire vegetative (green) roof
system.
measured in volume percent.
3.2.4.1 Discussion—A procedure for measuring the maxi-
5.2 Determining these performance characteristics of veg-
mum media water retention is provided in Test Method
etative (green) roof systems provides information to facilitate
E2399/E2399M.
the assessment of related engineering aspects of the facility.
Such aspects may include structural design requirements,
3.2.5 module, n—modular vegetative (green) roof systems
mechanical engineering and thermal design requirements, and
combine many functional elements of vegetative (green) roof
fire and life safety requirements.
systems in a pre-manufactured module.
3.2.5.1 Discussion—Independent modules are designed to
5.3 Determining these performance characteristics of veg-
be placed adjacent to one another and linked in order to tile
etative (green) roof systems provides information to facilitate
larger surfaces.
assessment of the performance of one vegetative (green) roof
system relative to another.
3.2.6 retained water, n—water which is held for a period of
hours or days but would eventually drain out given enough
6. Apparatus
time in the absence of evaporation or plant transpiration.
3.2.6.1 Discussion—Retained water is the quantity of water 6.1 Apparatus:
that is held for a prolonged period against gravity drainage in 6.1.1 Scale, accurate to 0.005 oz [0.14 g];
E2397/E2397M − 19
3 3
6.1.2 Metal mesh with sieve opening size of U.S. #30 and dry media density, D , both measured in lb/ft [kg/m ],
dry
[0.6 mm], or larger, suspended from a drain stand; and the maximum media water retention (MMWR), measured
6.1.3 Pan; and in volume percent. Multiply the maximum media density times
6.1.4 Water bath. the thickness of the media layer in feet [metres] to convert to
2 2
2 2
unit weight in lb/ft [kg/m ], and record. This is the unit
6.2 Units of measure: lb/ft [kg⁄m ].
weight of the growth media. Multiply the dry media density
times the thickness of the media layer in feet to convert to unit
7. Procedure
2 2
weight in lb/ft [kg/m ], and record. This is the dry unit weight
7.1 Weight of All Non-Absorptive Sheet Component—These
of the growth media. To determine the unit weight of the
materials include plastic or rubber membranes, closed-cell
retained water, Wr, multiply the MMWR by the thickness of
foam layers, and the rigid or semi-rigid plastic cores of
the media layer in feet and by 0.624 [10] and record this unit
2 2
geocomposite drain layers. Also included is insulation pro-
weight in lb/ft [kg/m ].
vided as part of protected membrane roofing (PMR) installa-
7.5 Weight of Granular Drainage Media:
tion. Absorptive drainage mats and fabrics, including fabrics
integrated with geocomposite drain layers, are excluded (see
7.5.1 Drain Layers Consisting Entirely of Granular Drain-
7.2 and 7.3). As needed, remove fabrics bonded to geocom- age Media—UseTestMethodE2399/E2399Mtodeterminethe
posite drain layers for separate measurement according to 7.2.
MMD and dry media density, D , both measured in lb/ft
dry
Weigh a 4-in. by 4-in. [10-cm by 10-cm] piece. Multiply this [kg/m ], and the MMWR of the granular material, measured in
2 2
weight by 9 [100] to convert to unit weight in lb/ft [kg/m ],
volume percent. Multiply the MMD times the thickness of the
and record.
granular drainage media in feet [metres]. Record the unit
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E2397/E2397M − 15 E2397/E2397M − 19
Standard Practice for
Determination of Dead Loads and Live Loads Associated
with Vegetative (Green) Roof Systems
This standard is issued under the fixed designation E2397/E2397M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers a standardized procedure for predicting the system weight of a vegetative (green) roof system.
1.2 The practice addresses the loads associated with vegetative (green) roof systems. Components that are typically encountered
in vegetative (green) roof systems include: membranes, non-absorptive plastic sheet components, metallic layers, fabrics,
geocomposite drain layers, synthetic reinforcing layers, cover/recover boards, insulation materials, growth media, granular
drainage media, and plant materials.
1.3 This practice also addresses the weight of the vegetative (green) roof system under two conditions: (1) weight under drained
conditions after new water additions by rainfall or irrigation have ceased (this includes the weight of retained water and captured
water), and (2) weight when rainfall or irrigation is actively occurring and the drain layer is completely filled with water. The first
condition is considered the dead load of the vegetative (green) roof system. The difference in weight between the first and second
conditions, approximated by the weight of transient water in the drain layer, is considered a live load.
1.4 This practice does not address point or line loads associated with architectural elements that are not essential components
of a particular vegetative (green) roof system. These architectural elements may include pavement, walls, and masonry, and so
forth.
1.5 This practice does not address live loads associated with construction activities.
1.6 This practice does not address loads associated with snow or wind.
1.7 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and to determine the
applicability of regulatory limitations prior to use.
1.9 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves
E631 Terminology of Building Constructions
E2114 Terminology for Sustainability Relative to the Performance of Buildings
E2396E2396/E2396M Test Method for Saturated Water Permeability of Granular Drainage Media [Falling-Head Method] for
Vegetative (Green) Roof Systems
E2398E2398/E2398M Test Method for Water Capture and Media Retention of Geocomposite Drain Layers for Vegetative
(Green) Roof Systems
This Practice is under the jurisdiction of ASTM Committee D08 on Roofing and Waterproofing and is the direct responsibility of Subcommittee D08.24 on Sustainability.
Current edition approved June 1, 2015Feb. 1, 2019. Published July 2015March 2019. Originally approved in 2005. Last published in 20112015 as E2397 – 11.E2397/
E2397M – 15. DOI: 10.1520/E2397_E2397M-15.10.1520/E2397_E2397M-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2397/E2397M − 19
E2399E2399/E2399M Test Method for Maximum Media Density for Dead Load Analysis of Vegetative (Green) Roof Systems
3. Terminology
3.1 Definitions:
3.1.1 For terms related to building construction, refer to Terminology E631.
3.1.2 For terms related to sustainability relative to the performance of buildings, refer to Terminology E2114.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 captured water, n—the quantity of water that is retained in the drain layer of a vegetative (green) roof system after new
water additions have ceased and that cannot escape the roof except through evaporation or plant transpiration.
3.2.1.1 Discussion—
Water capture is a design technique for enhancing the water holding properties of a vegetative (green) roof system. Water may be
captured using a number of techniques, including reservoirs built into a geocomposite drain layer, trays, and restricting drainage
in order to hold water within the drain layer. In some vegetative (green) roof systems a granular course at the bottom of the
vegetative (green) roof system provides both drainage and water capture functions. In this case the captured water applies only to
the thickness of the granular course for which drainage is restricted. A method for determining the captured water associated with
geocomposites based on the unit water capture volume is provided in Test Method E2398E2398/E2398M. The quantity of captured
water will depend on whether or not the upper surface of the geocomposite drain layer is in-filled with granular media.
3.2.2 geocomposite drain layer, n—a synthetic sheet, mat, or panel that is specifically designed to convey water horizontally
toward the roof deck drains, gutters, or scuppers.
3.2.2.1 Discussion—
Geocomposite drain layers include absorptive drain mats whose principle function is drainage, but which will also contribute to
water retention (see retained water). Some geocomposite drain layers may incorporate reservoirs on their upper surfaces that will
capture water (see captured water).
3.2.3 maximum media density, n—the density of a mixed media material determined after it has been subjected to a specific
amount of compaction and hydrated by immersion to simulate prolonged exposure to both foot traffic and rainfall.
3.2.3.1 Discussion—
The maximum media density applies to media in a drained condition. The measurement of the maximum media density is provided
in Test Method E2399E2399/E2399M.
3.2.4 maximum media water retention—the quantity of water held in a media layer at the maximum media density, measured
in volume percent.
3.2.4.1 Discussion—
A procedure for measuring the maximum media water retention is provided in Test Method E2399E2399/E2399M.
3.2.5 module, n—modular vegetative (green) roof systems combine many functional elements of vegetative (green) roof
systems in a pre-manufactured module.
3.2.5.1 Discussion—
Independent modules are designed to be placed adjacent to one another and linked in order to tile larger surfaces.
3.2.6 retained water, n—water which is held for a period of hours or days but would eventually drain out given enough time
in the absence of evaporation or plant transpiration.
3.2.6.1 Discussion—
Retained water is the quantity of water that is held for a prolonged period against gravity drainage in a vegetative (green) roof
system, or in one of its components, after new additions by rainfall or artificial irrigation have ceased. Neglecting the effects of
capillary rise, evaporation, and plant transpiration all of this water would eventually produce runoff. However, in practice most of
E2397/E2397M − 19
this water will not become runoff but will be lost to evaporation and the plant-mediated processes of transpiration. This procedure
describes standardized methods for estimating the quantity of water retained in a vegetative (green) roof system.
3.2.7 roof system, n—see roofing system.
3.2.8 roofing system, n—assembly of interacting components designed to weatherproof, and sometimes to insulate, the roof
surface of a building. E631
3.2.8.1 Discussion—
This term includes all components above the roof deck that are not part of the overlying vegetative (green) roof system. In practice
this usually means the waterproofing membrane and all materials below the waterproofing membrane, down to the structural deck.
It may include structural materials such as cover/recover board, insulation, protective layers, fire-suppressing materials, and
waterproofing materials. The weight of these components (assumed dry) must be obtained from the manufacturer of the roofing
system.
3.2.9 transient water, n—the quantity of water that is required to completely fill the drain layer of a vegetative (green) roof
system, less the quantity of captured water.
3.2.9.1 Discussion—
Transient water fills the open space, including pore spaces. This water can only be held for a period of minutes and drains
immediately when rainfall additions end. This moisture contributes to the live load of the vegetative (green) roof system.
4. Summary of Practice
4.1 This practice describes a systematic procedure for estimating the dead load and transient water live load of vegetative
(green) roof systems using information about the vegetative (green) roof components that are available from laboratory analysis.
5. Significance and Use
5.1 This practice addresses performance characteristics for vegetative (green) roof systems with respect to the dead load and
transient water load of the entire vegetative (green) roof system.
5.2 Determining these performance characteristics of vegetative (green) roof systems provides information to facilitate the
assessment of related engineering aspects of the facility. Such aspects may include structural design requirements, mechanical
engineering and thermal design requirements, and fire and life safety requirements.
5.3 Determining these performance characteristics of vegetative (green) roof systems provides information to facilitate
assessment of the performance of one vegetative (green) roof system relative to another.
6. Apparatus
6.1 Apparatus:
6.1.1 Scale, accurate to 0.005 oz [0.14 g];
6.1.2 Metal mesh with sieve opening size of U.S. #30 [0.6 mm], or larger, suspended from a drain stand;
6.1.3 Pan; and
6.1.4 Water bath.
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6.2 Units of measure: lb/ft [kg ⁄m ].
7. Procedure
7.1 Weight of All Non-Absorptive Sheet Component—These materials include plastic or rubber membranes, closed-cell foam
layers, and the rigid or semi-rigid plastic cores of geocomposite drain layers. Also included is insulation provided as part of
protected membrane roofing (PMR) installation. Absorptive drainage mats and fabrics, including fabrics integrated with
geocomposite drain layers, are excluded (see 7.2 and 7.3). As needed, remove fabrics bonded to geocomposite drain layers for
separate measurement according to 7.2. Weigh a 4-in. by 4-in. [10-cm by 10-cm] piece. Multiply this weight by 9 [100] to convert
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to unit weight in lb/ft [kg/m ], and record.
7.2 Weight of All Fabrics—Weigh a 4-in. by 4-in. [10-cm by 10-cm] sample in the dry condition. Multiply this weight
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by 9 [100] to convert to unit weight in lb/ft [kg/m ], and record. This is the dry unit weight of the fabric. Immerse the sample
in a water bath for 15 min. Withdraw from the bath and drain for 15 min by laying the fabric flat on a suspended U.S. #30 [0.6 mm]
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wire cloth or sieve. Weigh the sample, convert to unit weight in lb/ft [kg/m ], and record. This is the unit weight of the fabric.
The difference between the two measurements is the unit weight of the retained water associated with the fabric, Wr.
7.3 Weight of Absorptive Drain Mats Used as Drain Layer Components—These materials include open-cell foam layers, porous
mats fabricated from particles of plastic or rubber, and mats manufactured from coir or other organic fibers. Weigh the pan using
E2397/E2397M − 19
the scale. Weigh a 4-in. by 4-in. [10-cm by 10-cm] sample in the dry condition. Multiply thi
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