ASTM D7492/D7492M-16a(2024)

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: D7492/D7492M − 16a (Reapproved 2024)
Standard Guide for
Use of Drainage System Media with Waterproofing Systems
This standard is issued under the fixed designation D7492/D7492M; 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 mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.1 This guide makes recommendations for the selection
and application of prefabricated drainage media used in con-
2. Referenced Documents
junction with waterproofing systems on horizontal and vertical
2.1 ASTM Standards:
surfaces. Drainage media considered include rigid and semi-
C165 Test Method for Measuring Compressive Properties of
rigid insulation boards and rigid materials including plastics.
Thermal Insulations
This guide considers drainage media as it relates to the
C898/C898M Guide for Use of High Solids Content, Cold
performance of the waterproofing system, so its primary focus
Liquid-Applied Elastomeric Waterproofing Membrane
is draining water away from the membrane. This guide does
with Separate Wearing Course
not cover in detail other aspects or functions of drainage
C981 Guide for Design of Built-Up Bituminous Membrane
system performance such as efficiency of soil dewatering. The
Waterproofing Systems for Building Decks
scope of this guide does not cover other drainage media
C1471/C1471M Guide for the Use of High Solids Content
including gravel and filter fabric systems that can be con-
Cold Liquid-Applied Elastomeric Waterproofing Mem-
structed. The scope of this guide does not cover drainage
brane on Vertical Surfaces
materials or drainage system designs used for vegetative roof
D896 Practice for Resistance of Adhesive Bonds to Chemi-
systems. Vegetative roof systems require specialized designs.
cal Reagents
1.2 The committee with jurisdiction over this standard is not
D1079 Terminology Relating to Roofing and Waterproofing
aware of any other comparable standards published by other
D2434 Test Methods for Measurement of Hydraulic Con-
organizations.
ductivity of Coarse-Grained Soils
D3273 Test Method for Resistance to Growth of Mold on the
1.3 The values stated in either SI units or inch-pound units
Surface of Interior Coatings in an Environmental Cham-
are to be regarded separately as standard. The values stated in
ber
each system may not be exact equivalents; therefore, each
D3385 Test Method for Infiltration Rate of Soils in Field
system shall be used independently of the other. Combining
Using Double-Ring Infiltrometer
values from the two systems may result in nonconformance
D4511 Test Method for Hydraulic Conductivity of Essen-
with the standard.
tially Saturated Peat
1.4 This standard may involve hazardous materials, opera-
D4630 Test Method for Determining Transmissivity and
tions and equipment. This standard does not purport to address
Storage Coefficient of Low-Permeability Rocks by In Situ
all of the safety concerns, if any, associated with its use. It is
Measurements Using the Constant Head Injection Test
the responsibility of the user of this standard to establish
D4716/D4716M Test Method for Determining the (In-plane)
appropriate safety, health, and environmental practices and
Flow Rate per Unit Width and Hydraulic Transmissivity
determine the applicability of regulatory limitations prior to
of a Geosynthetic Using a Constant Head
use.
D5898/D5898M Guide for Standard Details for Adhered
1.5 This international standard was developed in accor-
Sheet Waterproofing
dance with internationally recognized principles on standard-
D6622/D6622M Guide for Application of Fully Adhered
ization established in the Decision on Principles for the
Hot-Applied Reinforced Waterproofing Systems
Development of International Standards, Guides and Recom-
E154/E154M Test Methods for Water Vapor Retarders Used
in Contact with Earth Under Concrete Slabs, on Walls, or
as Ground Cover
This guide is under the jurisdiction of ASTM Committee D08 on Roofing and
Waterproofing and is the direct responsibility of Subcommittee D08.22 on Water-
proofing and Dampproofing Systems. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Jan. 1, 2024. Published January 2024. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2011. Last previous edition approved in 2016 as D7492/D7492M – 16a. Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D7492_D7492M-16AR24. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7492/D7492M − 16a (2024)
3. Terminology consist of one or more of the following basic components. The
basic components of typical drainage medium are a mounting
3.1 Refer to Terminology D1079 for definitions of terms
surface that is placed against the waterproofing membrane to
used in this guide.
prevent embedment of the media, a porous core that provides
a drainage path, and a filter surface, often a fabric bonded over
4. Summary of Practice
the porous core to prevent clogging of the drainage paths.
4.1 This guide describes a method to estimate the amount of
Fibrous and foam drainage media are homogeneous materials
water a drainage system may need to carry. The guide also
that are sufficiently dense that they can be placed directly
offers descriptions of the various drainage systems in existence
against the waterproofing membrane. However, fibrous and
today along with suggestions on how different building situa-
foam media may not function properly in horizontal or nearly
tions will require different performance characteristics from the
horizontal (<30°) orientations. Other foam boards merely
drainage medium chosen. Items to be aware of during the
provide periodic grooves creating paths to drain water away
installation of drainage systems are also covered along with
from the waterproofed surface. Where appropriate, a protection
illustrations of typical drainage systems.
board should be installed between the waterproofing and
drainage media to reduce embedment of drainage media into
5. Significance and Use
the waterproofing.
5.1 This guide provides information and guidelines for the
6.4 The drainage media selection should include a consid-
selection and installation of drainage systems media that are in
eration of the forces that will be placed on it, such as backfill
conjunction with waterproofing systems. This guide is intended
pressure, gravity loads, and shear loads both initially and over
to be used in conjunction with Guides C898/C898M, C981,
the expected useful life of the assembly.
C1471/C1471M, D5898/D5898M, and D6622/D6622M and to
provide guidelines for the total waterproofing and drainage
6.5 The construction of drainage media should be consid-
system.
ered relative to the strength and protection of the waterproofing
membrane. The bearing surface of drainage media should place
6. General
no sharp edges against the waterproofing membrane, which
6.1 In selecting a drainage medium for use with could puncture, abrade the membrane, or imprint itself in the
waterproofing, consideration should be given to the design of
membrane. The filter fabric and its bond to the drainage
the waterproofing system. In particular orientation of the medium core should resist impact, compressive, and shear
system, attachment recommendations, connections to interior
loads imposed by backfilling and compaction, and temporary
and exterior drainage systems, and external loads applied to the and permanent construction loads.
system. Additional considerations include the materials and
6.6 The drainage media should always be placed next to the
construction over the drainage medium, installation
waterproofing. This location minimizes the hydrostatic head on
recommendations, durability, and penetrations and joints. (See
top of the waterproofing. If insulation is required the insulation
Figs. 1-3.) In all designs, the potential slip planes should be
shall be specified to handle the environment that is present
considered.
outside the drainage media and waterproofing membrane. If the
6.2 Compatibility—It is essential that all components and
insulation is porous, the drainage media must allow the porous
contiguous elements of the waterproofing system are compat-
insulation to drain any water accumulated during construction
ible and that the design of the system’s waterproofing and
or during its service on the wall into either the drainage media
drainage is coordinated to form an integrated waterproofing
or the footing drain tile system. A non-porous insulation is any
system.
insulation with closed cells that prevent water from flowing in
or out, for example extruded polystyrene foam or polystyrene
6.3 Basic Components—The various types of drainage me-
foam bead boards. A porous insulation is any insulation that
dia available are outlined in Section 12 of this guide and all
has open channels that easily allow water to enter and leave the
insulation such as rigid fiberglass boards with a perm rating of
4.6 Darcy (k, mm/s) or more (see X1.1.3).
7. Drainage Capacity
7.1 General—The drainage capacity is the volume of water
that passes through drainage media in a specified direction
under a known hydraulic gradient. The two major drainage
capacities of interest are the in-plane and through-the-face
drainage capacities. The orientation of the media and any slope
of the substrate will have a major effect on the drainage
capacity.
7.1.1 Through-the-Face Drainage—Through-the-face
drainage is the flow or seepage of water perpendicular to the
longitudinal axis of the drainage media. When media are
FIG. 1 Drainage at Lot Line Below-Grade Wall installed in a horizontal orientation, through-the-face drainage
D7492/D7492M − 16a (2024)
NOTE 1—Or slotted drains with ⁄2 in. slots.
FIG. 2 Drain in Plaza with Solid Surfacing
7.1.3 Resistance to Clogging—Drainage media should resist
clogging or silting of the media filter or other openings. The
function of the filter surface is to prevent excess soil or other
materials from entering the drainage media and impeding
in-plane drainage. In applications where removal of water from
the overburden (through-the-face drainage) is an expected
function of the drainage media, avoiding clogging of the filter
surface itself is just as important. Selection of the media to
resist clogging should be based on the particle-size distribution
of the material(s) placed adjacent to the filter media. If the filter
FIG. 3 Drain in Plaza with Paver and Pedestal Surfacing
opening size is large relative to the majority of adjacent
particles, the adjacent particles will pass though the filter media
and may, in time, clog the media. A correctly selected filter
may occur due to cracks, joints, or other openings in the
media should permit some fine particles to pass through the
material(s) placed atop the media or due to the normal
face of the media but retain a layer of larger particles at its
permeability of the material(s) such as soil. Through-the-face
surface until a filter cake is established. The fine particles
drainage capacity is critical to the drainage system’s efficiency
within the media will eventually be flushed from the media. As
at removing water from the overburden, which may affect the
for determining which fabric should be used, there are a
performance and durability of the overburden, but is less
number of resources that may be used if the particle-size
relevant to waterproofing membrane performance. In applica-
distribution is known. Several geotextile manufacturers have
tions where removal of water from the overburden is an
brochures and spec data sheets for different types of fabrics that
expected function of the drainage media, the filter surface,
contain information on how to choose the right geotextile for
whether fabric or the base material, should have adequate
the given situation. Another fabric may be needed to handle
porosity so as not to restrict drainage through the face of the
particular soils or situations with fine laden overburden. Recent
media.
civil engineering handbooks (see Note 1) have sections de-
7.1.2 In-plane Drainage—In-plane drainage is the flow or
voted to the selection of geotextiles for filtration and water
seepage of water within and along the plane of the drainage
drainage among other topics. Some handbooks on drainage
media and refers to the ability of the drainage media to remove
system design recommend designing the drainage system
whatever water makes it through the overburden and into the
assuming the filter fabric is 50 % clogged.
drainage media. In-plane drainage helps the performance of
7.1.4 Long-Term Performance—The materials used for
most membrane waterproofing systems by minimizing the
drainage media must be capable of surviving the environment
exposure of the membrane to hydrostatic pressure. In horizon-
in which they are placed for at least the life of the waterproof-
tal orientations, the hydraulic gradient will be relatively low.
ing system. The physical properties of the media that relate to
Therefore, the drainage paths or pores in the media should be
drainage capacity, such as compressive strength, shear
relatively large to ensure the media does not hold water due to
strength, resistance to biological deterioration, and freeze-thaw
surface tension and capillary forces.
resistance must be sustained throughout the service life of the
7.1.2.1 To determine the drainage capacity needed, the
media.
designer should be familiar with the climate, terrain, adjacent
buildings, and structures that could redirect rain water or run 7.1.5 Another performance issue arises when installing
off onto the area that has to be drained, whether there is soil drainage media on “vegetative roof system” or garden patio
overburden on the drainage media, etc. Appendix X1 contains situations. Consideration must be given on how the drainage
methods that could be used to calculate the capacity needed for media will either stop root penetration or how the roots from
the drainage system. In no way does Appendix X1 contain all large plants and small trees will affect the performance of the
the different methods for calculating the capacity needed by a drainage media. How this is accomplished along with other
drainage system; other met
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