18th Westford Symposium 2014 August 6, 2014

Osmosis: The Bane of Liquid Applied

Waterproofing Membranes
WESTFORD SYMPOSIUM SUMMER CAMP 2014:
GRAHAM FINCH, MASC, P.ENG
PRINCIPAL, BUILDING SCIENCE RESEARCH SPECIALIST, RDH BUILDING ENGINEERING

Outline

The Waterproofing Conundrum

Proving It

Testing It

Measuring It

Findings to Date

What to Look for?

What Next?

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Inquisitive:
definition: eager to learn or learn more, to be curious,
desire to solve problems..…engineers!

Inquisitive at a Young Age

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Inquisitive & Loaded with

Cool Tools at Career Age

Colleague Brian Hubbs being stuffed up in a hole by Silvio

Plescia to perform air leakage testing… Definitely Inquisitive

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18th Westford Symposium 2014 August 6, 2014

The Waterproofing
Conundrum

Vancouver c. 2004 – 5 year roof review

Really Heavy
Pink Stuff

Liquid Waterproofing
over Concrete Deck

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30-60 mil Liquid Applied Waterproofing

Water Filled Blisters

Under Pressure

Membrane Cut & Water

Released from Blister

Liquid Water Below Membrane &

Reported Intermittent Leaks

Lots of water below

the membrane

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Problematic Roof Assemblies Affected

Concrete Pavers, Ballast, or

Dirt/Green Roof

Pedestals (optional)

Filter Fabric

XPS Insulation (over heated
space)

Drainage Mat (optional)

Liquid membrane

Concrete roof slab

Blistering observed over both conditioned (interior) and

unconditioned space (parking garages), within planters,
green roofs, and water features

2004 - Evaluating the Problem

Systemic failure of 5 year old

waterproofing membrane
throughout massive 4 tower
residential complex

Just one of many buildings
affected that we were aware of

Cause of the blistering unknown
at the time

Apparent correlation with
membrane thickness

Initial monitoring & research
started

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2004 – Membrane “Blistering Index”

>90 mils okay?

Vancouver c.2008 The Problem Grows…

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Blisters Everywhere you Dig!

Gallons of Water Beneath Membranes

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Leaks, Lawsuits &

Membrane Renewals

Membrane Blisters Lifting Pavers & Leaks

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Membrane Blisters Lifting Pavers & Leaks

Paver Water Beds!

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Polyurethane Membrane
Blisters in Water Features

2008 – Updated Blister Index

12 10
11

2004 2008

12

10

Nothing below 50%

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2008 – State of Affairs

Systemic issue affecting mostly asphalt modified

polyurethane membranes in protected membrane
roofs over concrete decks

2 similar membranes from 2 major manufacturers

Findings – Water Filled Blisters

Membranes 3 to 15 years old with blisters

Membranes 30-60 mils, some up to 120 mils

Blisters filled with water under pressure

Blisters range from penny size to entire roof deck areas

No obvious detail or discontinuity

Top of membrane almost always wet

Ability to lift pavers, expand/grow over time

Theories & Urban Legends

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Industry Perception Pre 2008

Many hypotheses and

strong opinions as to the
blistering mechanisms

Little building science
understanding or research
– lots of speculation

Blame fell to many roofers
and the liquid membrane
manufacturers

Reports of problems
worldwide

Theory #1: Pinholes in Thin Membrane

? In but not out

X
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Theory #2: Hydrostatic Head from Details

X
? Self contained fully
adhered blisters far
away from any details

Theory #3: Vapor Diffusion from Inside

OUTDOORS

X
OUT

IN

INDOORS

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Theory #4: Diffusion & Capillary from Outside

OUTDOORS

X
OUTSIDE &
BLISTER
WATER
EQUAL

INDOORS

Hypothesis: Osmosis

Osmosis developed as a possible hypothesis after

debunking all other options

Osmosis is the flow of water across a semi-permeable

membrane from the side of low to high salt (solute)
concentration

Requires 2 things:

Difference in salt (solute, metal ion) concentration

A membrane permeable to water molecules, but with pore
structure too small for dissolved ions to pass

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What is Osmosis?

Membrane Applied Pressure

Osmotic
Pressure

Salty Fresh Salty Fresh Salty Fresh

Water Water Water Water Water Water

Osmosis: Equilibrium: Reverse Osmosis:

Water flows through Osmotic pressure is the Mechanical pressure greater
membrane from lower to pressure required to stop than the natural osmotic
higher dissolved salt Ion water flow and reach pressure is applied to filter
concentration equilibrium across membrane dissolved salt ions out and
create fresh water

Osmosis in Other Applications

Not well documented by

building/roofing industry

Either rare or unreported

Other industries:

Fiberglass boat hulls
• Uncured resins create
chemical osmotic cell

Epoxy Floor Coatings
• Moisture from slabs on
grade create blisters
beneath certain
membranes

Bridge decks
• De-icing salts cause
blistering of coatings

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Could it Be Osmosis?

Questions to answer:

Is the blister water salty?

What is the osmotic pressure difference between rainwater
and blister water?

Is the waterproofing membrane semi-permeable?

Industry resources available

Reverse Osmosis filter industry – formulas/calculators for
reverse osmosis system pressures based on dissolved salt
concentrations

Visual/ microscope & vapor permeance testing (ASTM E96)
for relative permeability of membrane

Water Extraction For Testing

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Is the Blister Water Salty?

Blister water extracted from several

roofs & sent to 3rd party water lab

Blister water found to contains high
concentrations of dissolved metals:

Sodium: naturally occurring within
cement and aggregates

Potassium: potash used within
concrete additive

Silicon: naturally occurring within
cement and aggregates

Rainwater from ponding water - no
relevant concentration of minerals

What is the Osmotic Pressure Potential?

Blister water contains: Sodium, Potassium,

Silicon and traces of other dissolved minerals
including Boron, Magnesium, Tin and other
stuff!

Calculated osmotic suction pressures for
different blister water samples found to range
from 300 to 400 kPa (43 to 58 psi)!

Reinforces finding that water extracted
from membrane blister tended to be under
some positive pressure

As blisters form and grow, the membrane
delaminates – so full pressures are never
realized

For reference – brackish water = 25 kPa
(3.6 psi), seawater 2500 kPa (363 psi)

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Membrane Removal

Is the Membrane Permeable?

Membrane #1 – Aged 30 mil moisture cure chemistry, removed from roof

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Is the Membrane Permeable?

Membrane #2 – Aged 60 mil moisture cure chemistry, removed from roof

Is the Membrane Permeable?

Many manufacturers were in 2008 and still are today

reporting ASTM E96 vapor permeance ‘dry-cup’ values

Tested both aged (removed from site) and new (laboratory
made) membrane samples for each

Tested: dry, wet, and inverted wet cup

Lab, 50% RH Lab, 50% RH Lab, 50% RH

100% RH, water

0% RH, Desiccant 100% RH, water

DRY CUP – WET CUP – Inverted WET CUP –

Average RH = 25% Average RH = 75% Average RH = 75% + H20

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Are These Membranes Permeable?

V APOR P ERMEANCE OF L IQU ID M EM BRANES

8
VAPOR PERMEANCE - US PERMS

6
Aged Membrane 1
- 30 mils
5
Aged Membrane 2
4 - 60 mils
New Membrane 3 -
3 120 mils
SBS/Hot Rubber
2

0
DRY CUP WE T C U P I N VE R TE D WE T
CUP

Impact of High Vapor Permeance

How does the concrete get wet or water initially get

below the membrane to create the osmotic cell?
1. Fresh cast concrete is initially saturated or rained on
2. Condensation & liquid water within bug holes and
unfilled surface voids below membrane
3. Vapor diffusion from topside of membrane – until water
& equilibrium on both sides

1 2 3

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Impact of High Vapour Permeance

WUFI SIMULATED MOISTURE CONTENT OF TOP 1/2" OF CONCRETE SLAB -

COMPARISON BY MEMBRANE TYPE
140
CONCRETE (KG/M 3)

wetting trend

120
Semi-permeable asphalt
modified polyurethane
waterproofing
OF
TOP SURFACE

100
IN

80
MOISTURE

Impermeable hot rubber

drying trend waterproofing

60
2000 2001 2002 2003 2004 2005 2006 2007

How to Measure Osmotic Flow Rate?

Membrane

Dissolved salt/metal ion
concentration difference √
across membrane?
Membrane permeable to

water?
√

Mechanism of initial
wetting?
√ Salty
Water
Fresh
Water

Measure osmotic flow

rate directly ? Measure movement of
water across
waterproofing membrane
with salt water from site

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Chamber Concepts: Version 1.0

Chamber Concepts: Version 1.1

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Chamber Concepts: Version 1.2

Chamber Concepts: Version 1.3

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Chamber Concepts: Versions 2.0 & 2.1

Chamber Concepts: Version 3.0

Sometimes simpler is better…

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Osmotic Flow Laboratory Apparatus

250 mL Glass container

with open screw-top lid

P atm P c = P atm

Salty Fresh
Water Water

Membrane Brass coated or plastic

screw-top lid
Initial Setup, Pressure within Container is
equal to atmospheric.

Increase in Volume = Flow

through Membrane Salty
Water Membrane bedded in
waterproof epoxy, epoxy
P c>P atm
P atm fills voids in screw top lid
and prevents unscrewing

Salty
Water Waterproofing Membrane
Fresh
Water

Membrane
Osmotic Flow

Osmosis occurs until Pressure within container

reaches the Osmotic Pressure

Proof of Concept Testing

Commercial reverse osmosis filter

Measured
volume/mass
rates up to
15 L/m2/day
per
manufacturers
specs

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At Last… Some Results

Measured Osmotic Flow – Control Samples

O SMOTIC F LOW T HROUGH M EMBRANE - I NFLUENCE OF O SMOTIC

P RESSURE P OTENTIAL
3000
OSMOTIC FLOW THROUGH MEMBRANE - g/m2

Membrane #1 - 0 M NaCl, water control sample

2500 Membrane #1 - 0.1 M NaCl - 460 kPa 9.7 g/m2/day

Membrane #1 - 1.0 M NaCl - 55,000 kPa

2000

1500
5.9 g/m2/day

1000

500 Control sample with no osmotic difference - moisture ~0 g/m2/day

uptake due to absorption into membrane only

0
0

50

100

150

200

250

300

DAYS FROM START OF TEST

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Measured Osmotic Flow – Blister Water

O SMOTIC F LOW T HROUGH M EMBRANE - I NFLUENCE OF O SMOTIC

P RESSURE P OTENTIAL
2000
OSMOTIC FLOW THROUGH MEMBRANE - g/m2

Membrane #1 - 0 M NaCl, water control sample

1800
Membrane #1 - 0.1 M NaCl - 460 kPa
1600
Membrane #1 - 1.0 M NaCl - 55,000 kPa
1400
Membrane #1 - Blister Water - 326 kPa
1200

1000

800

600

400

200

0
0

25

50

75

100

125

150
DAYS FROM START OF TEST

Aged Membrane Testing

AVERAGE O SMOTIC F LOW T HROUGH M EMBRANES #1 & #2

2000
Membrane #1 - 30 mil Aged
OSMOTIC FLOW RATE - g/m2

Membrane #2 - 60 mil Aged

1500

1000

500

0
0

25

50

75

100

125

150

DAYS FROM START OF TEST

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New vs Aged Membrane Testing

OSMOTIC FLOW THROUGH VARIOUS ASPHALT MODIFIED POLYURETHANE WATERPROOFING MEMBRANES

1600

1400 Membrane #1 - 30 mil - blistered

Same membrane
Aged - manuf. & chemistry Membrane #1 - 30 mil - blistered
1200
Blistered
Osmotic Flow Rate - g/m2

Membrane #2 - 60 mil - blistered

1000
Membrane #3 - 70 mil - blistered

800
Membrane #5 - 120 mil - unknown
performance
600
Membrane #7 - 60 mil - unknown
performance

400 Membrane #9 - 100 mil - unknown

performance

Membrane #10 - 100 mil - unknown

200
performance

0
0 20 40 60 80 100 120 140 160 180 200
# days from start of test
New – Unknown
Performance

Impacts of Primers?

EFFECT OF MEMBRANE PRIMER TYPE - POLYURETHANE VS EPOXY

400
Osmotic Flow through membrane - g/m2

350

300

250

200

150

100 Epoxy Primer on membrane - 0.5 Perms

50 Polyurethane Primer on membrane - 0.9 Perms

0
0 20 40 60 80 100 120 140 160 180 200 220 240 260

Days from Start of Test

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Findings – Original Membranes

Asphalt modified polyurethane membranes have serious

shortcomings as waterproofing

Vapor permeance typically >5 US Perms after aging, even if
initially <1 US perms

Osmotic Flow Rates of 5-12 g/m2/day,
(up to 20+ g/m2/day with some 10-15 year old membranes)

Aged values much worse than initial
• Impacts of alkaline environment and constant wetting?

Some primers effective at reducing flow rate, but difficult to
apply to sufficient thickness in field

Conclusion – if we could reduce osmotic flow rate to less than
the vapor diffusion rate through concrete slab then could we
be okay?

Summary: Osmotic Blistering Process

Top surface of the membrane wet all

year (insulation/dirt/water feature)

Moisture moves though the membrane
via vapor diffusion

Concrete less permeable than the
membrane = moisture accumulation

Moisture dissolves minerals from
concrete

Osmosis forms small blisters at
localized voids or de-bonded areas of
membrane

Osmotic pressure grows and continues
expanding blisters over time

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Worldwide Findings

RDH observations

Pacific Northwest to California

Reported Osmotic Blistering issues by others through
discussions and by our project involvement

Florida & Southern US

Hawaii

New Zealand

Europe & Asia

Appears more prevalent in temperate, humid climates –
where water is able to sit on membrane year-round

Or in ponds, planters and other wet places

Added to Hartwig Kuenzel’s Roofing Book

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LotsBlistered
Many of Repairs Made… With Other
Membrane MaterialsProjects
Renewals

A Little Caution About Roofers & Tie-ins…

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New and Ongoing Research

Between 2008 and 2014 we have worked with numerous

liquid applied membrane manufacturers to address osmosis

Measure osmotic flow rate, vapor permeance, absorption

Assess impacts of thickness, reinforcing, primers, fillers, cure
method, different chemistries, etc.

Looked at alternate membrane chemistries & membrane types
• 2 component & single component chemistries
• Polyurethanes (asphalt and non-asphalt modified)
• Polyureas
• Polyesters
• PMMAs
• Asphalt Emulsions

Continued testing of original two membrane offenders &
other membranes applied in past decade (litigation and R&D)

Laboratory Apparatus Revisions

Improved lid with

powder-coated
corrosion proof
finish & improved
epoxy seal to
keep water out of
gap & consistent
measurement

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What About Polyureas

What About Polyureas?

What About Polyureas?

VARIOUS POLYUREA MEMBRANES (7 TYPES) AVERAGED OSMOTIC FLOW RATES
1500
OSMOTIC FLOW THROUGH MEMBRANE, g/m²

1250
Aged asphalt modified
1000
urethane control sample

750

500 7 new different polyurea

chemistries
250

0
0 20 40 60 80 100 120
Days from Start of Test

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What About Polyureas

Membrane
Thickness: Osmotic Flow
Rate Water Inverted Vapour
Membrane Average, Permeance as
Absorption - % &
Sample mils Average, Time to Reach Measured:
Name g/m2/day Equilibrium
Range, mils US Perms
Range, g/m2/day

Grey 83 2.9 1.5%, <7 days 1.4 US Perms

Brown 78 2.0 2.0%, <7 days 2.2 US Perms

Beige 83 2.3 1.6%, <7 days 1.2 US Perms

Grey 2 135 2.9 0.6%, <7 days 1.9 US Perms

Grey 3 34 5.3 1.3%, <7 days 3.5 US Perms

Orange 106 2.3 1.2%, <7 days 1.2 US Perms

Green 74 2.9 1.6%, <7 days 2.1 US Perms

RED = BAD TRAIT, GREEN = DESIRABLE TRAIT

What About Other Chemistries?

What About Other Membrane Chemistries?

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What About Other Membrane Chemistries?

Vapour Permeance of
Membrane 100 mil Standard Water Absorption:
Sample Name Thickness: % by Mass Osmotic Flow Rate,
(US Perms) Thickness
Average, g/m2/day
Wet Cup Inverted At 20 days At 250 days
Wet Cup
AFU-Asphalt 0.08 0.08 US 1.6% >4.5% (has not
Free Urethane Perms stopped) ~0.7 (87 mils)
Resin US Perms

PE – Polyester 0.26 US 0.27 US 1.3% 0.2%

Based System Perms Perms 0.4 (55 mils)

PE2
Two component 0.31 US 0.33 US 1.7% 0.8%
Perms Perms 0.5 (54 mils)
polyester
system
PMMA –
0.27 US 0.28 US >4.4% (has not
Poly Methyl 1.7% ~0.8 (65 mils)
Perms Perms stopped)
MethAcrlyate

RED = BAD TRAIT, GREEN = DESIRABLE TRAIT, ORANGE - BORDERLINE

What About Asphalt Emulsions?

• 20% absorption by
weight after 210 days
and still rising, 20%
measured swelling
• Osmostic flow rate:
~5.4 g/m2/day
• Inverted wet cup
permeance 0.14 US
perms for 121 mils

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Asphalt Emulsion Waterproofing?

Comparison of Results to Date

INVERTED WET CUP VAPOR PERMEANCE VS OSMOTIC FLOW RATE - COMPARISON

OSMOTIC FLOW RATE - g/m2 (ALL SALT SOLUTIONS)

20

18

16

14

12

10

0
0 1 2 3 4 5 6 7 8 9 10
Inverted Wet Cup Vapor Permeance - US Perms
Aged Asphalt Modified Polyurethane Membranes - Where Blistering Observed
New Asphalt Modified Polyurethane Membranes - Unknown Performance
New Polyurea Membranes - Unknown Performance
New Membrane Chemistries - 1 and 2 component - Unknown performance

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Comparison of Results to Date

OSMOTIC FLOW RATE - g/m2 (ALL SALT SOLUTIONS) INVERTED WET CUP VAPOR PERMEANCE VS OSMOTIC FLOW RATE - COMPARISON
4.0

3.5

3.0 Targets:
<0.1 US perms,
2.5
<0.1 g/m2 Osmotic Rate
2.0 Plus minimal absorption
1.5

1.0

0.5

0.0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Inverted Wet Cup Vapor Permeance - US Perms
Aged Asphalt Modified Polyurethane Membranes - Where Blistering Observed
New Asphalt Modified Polyurethane Membranes - Unknown Performance
New Polyurea Membranes - Unknown Performance
New Membrane Chemistries - 1 and 2 component - Unknown performance

Revised Test Procedure & Targets

Key Measurements:

Vapor Permeance – Inverted wet cup testing (<0.1 perms, want
this to be less than the concrete slab)

Osmotic Flow Rate – measure by apparatus with control salt
solution for 3-6 months (<0.1 g/m2/day)

Water Absorption – soak it until it stops (<1%)

Osmotic Flow
= >
Rate <
VS.
Concrete
Vapour
Diffusion Rate

√ ? X

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Recommendations

Avoid use of cold applied membrane chemistries over

concrete in a protected roof or environment where top of
membrane will be wet (roof, pond, split-slab, planter etc.)

Be very careful of membranes made for “green concrete” as
tend to be worse (higher vapor permeance)

Not just a black asphalt modified membrane problem –
affects all types – polyureas, polyurethanes, PMMAs etc.

In meantime use a good tried and true fully adhered system –
use hot rubber, 2 Ply SBS, built-up asphalt etc.

Where “hands-tied”, keep water from getting down to liquid
waterproofing (supplemental drainage above insulation)

Some Conversions

Desired Inverted Wet Cup Vapor permeance to be less than

0.1 US Perms (<6 ng/Pa s m2)

Few manufacturers report inverted wet cup, usually just wet
cup (Procedure B) (or worse still dry cup, Procedure A)

Inverted wet cup values typically 10 to 50% higher than wet cup
and can be many times higher than dry cup values

Watch reporting units

1 mil = 1/1000”

1 mm = 25.4 mils

Permeability in perm-in : divide by thickness (inches)

WVT (grains/hr/ft2) not same units or value as vapor
permeance (grains/hr/ft2 inHg)

Convert to US perms for quick check

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Red Flags to Look Out For

2.3 US Perms!

Red Flags to Look Out For

Needs Updating!
Withdrawn standard

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Red Flags to Look out For

1.7 US Perms
(DRY CUP)

Red Flags to Look out for

No Permeance
measurements
anywhere

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Red Flags to Look out for

Two measurements?

0.72 WVT works out to ~ 1.8 US Perms (Wet cup)

1.56 WVT ~ 4.0 US Perms (Wet cup)

Next Steps

Determine maximum safe vapor permeance threshold for

waterproofing membranes over concrete

Refine and develop ASTM osmotic flow test method and determine
acceptable maximum flow rates for different applications.

Revise Applicable Standards (ASTM C836 and/or withdrawn
CAN/CGSB–37.58-M86) to specify:

Maximum allowable inverted wet cup permeance (<0.1 perms?)

Maximum absorption for constant & prolonged immersion (this
is not the typical 24 hr/7day ASTM test)

Maximum allowable osmotic flow rate (<0.1 g/m2, so less than
concrete can dry through)

Consideration for aging and submersion within wet concrete
environment (accelerated wet alkaline test?)

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Next Steps

Need a waterproofing industry champion to raise

awareness and push revisions to ASTM standards and
bring forth the osmosis test method

We gave been looking for a manufacturer with a cold
applied liquid membrane that works! (market advantage)

Testing and evaluation of all products currently on
market

Hopefully No More Problems!?

A Final Word of Warning

Roof over concrete parking garage in US

“New” 60/120 mil fluid applied waterproofing under
landscaping

Irrigation system/grass over waterproofing over
concrete

Assembly is <5 years old, applied to repair a previous
failure

Manufacturer claims “vapor drive from within the
substrate or hydraulic pressure beneath the
waterproofing membrane”

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Discussion + Questions

gfinch@rdh.com – 604-873-1181

rdh.com

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