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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
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Outline à The Waterproofing Conundrum
à Proving It
à Testing It
à Measuring It
à Findings to Date
à What to Look for?
à What Next?
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Inquisitive: definition: eager to learn or learn more, to be curious, desire to solve problems.. …engineers!
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The Waterproofing Conundrum
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Vancouver c. 2004 – 5 year roof review
Really Heavy Pink Stuff
Liquid Waterproofing over Concrete Deck
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Water Filled Blisters Under Pressure
30-60 mil Liquid Applied Waterproofing
Membrane Cut & Water Released from Blister
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Liquid Water Below Membrane & Reported Intermittent Leaks
Lots of water below the membrane
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Problematic Roof Assemblies Affected
à Concrete Pavers, Ballast, or
Dirt/Green Roof
à Pedestals (optional)
à Filter Fabric
à XPS Insulation (over heated
space)
à Drainage Mat (optional)
à Liquid membrane
à Concrete roof slab
Blistering observed over both conditioned (interior) and unconditioned space (parking garages), within planters, green roofs, and water features
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2004 - Evaluating the Problem
à Systemic failure of 5 year old
waterproofing membrane
throughout massive 4 tower
residential complex à Just one of many buildings
affected that we were aware of
à Cause of the blistering unknown
at the time à Apparent correlation with
membrane thickness
à Initial monitoring & research
started
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2004 – Membrane “Blistering Index”
>90 mils okay?
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Vancouver c.2008 The Problem Grows…
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Blisters Everywhere you Dig!
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Gallons of Water Beneath Membranes
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Leaks, Lawsuits & Membrane Renewals
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Membrane Blisters Lifting Pavers & Leaks
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Membrane Blisters Lifting Pavers & Leaks
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Paver Water Beds!
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Polyurethane Membrane Blisters in Water Features
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2008 – Updated Blister Index
10
12
12
10 11
2004 2008
Nothing below 50%
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2008 – State of Affairs
à Systemic issue affecting mostly asphalt modified polyurethane membranes in protected membrane roofs over concrete decks à 2 similar membranes from 2 major manufacturers
à Findings – Water Filled Blisters à Membranes 3 to 15 years old with blisters
à Membranes 30-60 mils, some up to 120 mils
à Blisters filled with water under pressure
à Blisters range from penny size to entire roof deck areas
à No obvious detail or discontinuity
à Top of membrane almost always wet
à Ability to lift pavers, expand/grow over time
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Theories & Urban Legends
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Industry Perception Pre 2008
à Many hypotheses and
strong opinions as to the
blistering mechanisms
à Little building science
understanding or research
– lots of speculation
à Blame fell to many roofers
and the liquid membrane
manufacturers
à Reports of problems
worldwide
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Theory #1: Pinholes in Thin Membrane
? In but not out
X
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Theory #2: Hydrostatic Head from Details
? Self contained fully adhered blisters far away from any details X
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Theory #3: Vapor Diffusion from Inside
INDOORS
OUTDOORS
OUT
IN X
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Theory #4: Diffusion & Capillary from Outside
INDOORS
OUTDOORS
OUTSIDE & BLISTER WATER EQUAL X
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Hypothesis: Osmosis
à Osmosis developed as a possible hypothesis after
debunking all other options
à Osmosis is the flow of water across a semi-permeable
membrane from the side of low to high salt (solute)
concentration
à Requires 2 things: à Difference in salt (solute, metal ion) concentration
à A membrane permeable to water molecules, but with pore
structure too small for dissolved ions to pass
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What is Osmosis?
Osmosis: Water flows through
membrane from lower to
higher dissolved salt Ion
concentration
Salty Water
Fresh Water
Fresh Water
Salty Water
Membrane
Osmotic Pressure
Fresh Water
Salty Water
Applied Pressure
Equilibrium: Osmotic pressure is the
pressure required to stop
water flow and reach
equilibrium across membrane
Reverse Osmosis: Mechanical pressure greater
than the natural osmotic
pressure is applied to filter
dissolved salt ions out and
create fresh water
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Osmosis in Other Applications
à Not well documented by
building/roofing industry à Either rare or unreported
à Other industries: à Fiberglass boat hulls
• Uncured resins create chemical osmotic cell
à Epoxy Floor Coatings • Moisture from slabs on
grade create blisters beneath certain membranes
à Bridge decks • De-icing salts cause
blistering of coatings
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Could it Be Osmosis?
à Questions to answer: à Is the blister water salty?
à What is the osmotic pressure difference between rainwater
and blister water?
à Is the waterproofing membrane semi-permeable?
à Industry resources available à Reverse Osmosis filter industry – formulas/calculators for
reverse osmosis system pressures based on dissolved salt
concentrations
à Visual/ microscope & vapor permeance testing (ASTM E96)
for relative permeability of membrane
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Water Extraction For Testing
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Is the Blister Water Salty?
à Blister water extracted from several
roofs & sent to 3rd party water lab
à Blister water found to contains high
concentrations of dissolved metals:
à Sodium: naturally occurring within
cement and aggregates
à Potassium: potash used within
concrete additive
à Silicon: naturally occurring within
cement and aggregates
à Rainwater from ponding water - no
relevant concentration of minerals
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What is the Osmotic Pressure Potential?
à Blister water contains: Sodium, Potassium,
Silicon and traces of other dissolved minerals
including Boron, Magnesium, Tin and other
stuff!
à Calculated osmotic suction pressures for
different blister water samples found to range
from 300 to 400 kPa (43 to 58 psi)!
à Reinforces finding that water extracted
from membrane blister tended to be under
some positive pressure
à As blisters form and grow, the membrane
delaminates – so full pressures are never
realized
à For reference – brackish water = 25 kPa
(3.6 psi), seawater 2500 kPa (363 psi)
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Membrane Removal
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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
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Is the Membrane Permeable?
à Many manufacturers were in 2008 and still are today
reporting ASTM E96 vapor permeance ‘dry-cup’ values
à Tested both aged (removed from site) and new (laboratory
made) membrane samples for each
à Tested: dry, wet, and inverted wet cup
Lab, 50% RH
0% RH, Desiccant
DRY CUP – Average RH = 25%
Lab, 50% RH
100% RH, water
WET CUP – Average RH = 75%
Lab, 50% RH
100% RH, water
Inverted WET CUP – Average RH = 75% + H20
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Are These Membranes Permeable?
0
1
2
3
4
5
6
7
8
DRY CUP WET CUP INVERTED WET CUP
VA
PO
R P
ER
MEA
NC
E -
US P
ER
MS
VAPOR PERMEANCE OF LIQUID MEMBRANES
Aged Membrane 1- 30 mils
Aged Membrane 2- 60 mils
New Membrane 3 -120 mils
SBS/Hot Rubber
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Impact of High Vapor Permeance
à 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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60
80
100
120
140
2000 2001 2002 2003 2004 2005 2006 2007
MO
IST
UR
EIN
TO
PS
UR
FA
CE
OF
CO
NC
RET
E(K
G/M
3)
WUFI SIMULATED MOISTURE CONTENT OF TOP 1/2" OF CONCRETE SLAB -COMPARISON BY MEMBRANE TYPE
Impermeable hot rubber waterproofing
Semi-permeable asphalt modified polyurethane waterproofing
Impact of High Vapour Permeance
drying trend
wetting trend
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How to Measure Osmotic Flow Rate?
à Dissolved salt/metal ion
concentration difference
across membrane?
à Membrane permeable to
water?
à Mechanism of initial
wetting?
à Measure osmotic flow
rate directly Osmosis: Water flows through membrane from lower to
higher dissolved salt Ion
concentration
SaltyWater
FreshWater
FreshWater
SaltyWater
Membrane
OsmoticPressure
Fresh
Water
Salty
Water
Applied Pressure
√
√
√
? Measure movement of water across waterproofing membrane with salt water from site
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Chamber Concepts: Version 1.0
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Chamber Concepts: Version 1.1
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Chamber Concepts: Version 1.2
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Chamber Concepts: Version 1.3
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Chamber Concepts: Versions 2.0 & 2.1
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Chamber Concepts: Version 3.0
Sometimes simpler is better…
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Osmotic Flow Laboratory Apparatus
Salty Water Fresh
Water Membrane
Increase in Volume = Flow through Membrane
Salty Water
Fresh Water
Membrane
Initial Setup, Pressure within Container is equal to atmospheric.
P atm
P atm
P c = P atm
P c >P atm
Osmosis occurs until Pressure within container reaches the Osmotic Pressure
Osmotic Flow
250 mL Glass container with open screw-top lid
Brass coated or plastic screw-top lid
Waterproofing Membrane
Membrane bedded in waterproof epoxy, epoxy fills voids in screw top lid and prevents unscrewing
Salty Water
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Proof of Concept Testing
Measured volume/mass rates up to
15 L/m2/day
per manufacturers
specs
Commercial reverse osmosis filter
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At Last… Some Results
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Measured Osmotic Flow – Control Samples
0
500
1000
1500
2000
2500
3000
0 50 100
150
200
250
300
OSM
OTIC FLOW THR
OUGH MEM
BRAN
E -‐g
/m2
DAYS FROM START OF TEST
OSMOTIC FLOW THROUGH MEMBRANE -‐ INFLUENCE OF OSMOTICPRESSURE POTENTIAL
Membrane #1 -‐ 0 M NaCl, water control sample
Membrane #1 -‐ 0.1 M NaCl -‐ 460 kPa
Membrane #1 -‐ 1.0 M NaCl -‐ 55,000 kPa
Control sample with no osmotic difference - moisture uptake due to absorption into membrane only
9.7 g/m2/day
5.9 g/m2/day
~0 g/m2/day
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Measured Osmotic Flow – Blister Water
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 25 50 75 100
125
150
OSM
OTIC FLOW THR
OUGH MEM
BRAN
E -‐g
/m2
DAYS FROM START OF TEST
OSMOTIC FLOW THROUGH MEMBRANE -‐ INFLUENCE OF OSMOTICPRESSURE POTENTIAL
Membrane #1 -‐ 0 M NaCl, water control sample
Membrane #1 -‐ 0.1 M NaCl -‐ 460 kPa
Membrane #1 -‐ 1.0 M NaCl -‐ 55,000 kPa
Membrane #1 -‐ Blister Water -‐ 326 kPa
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Aged Membrane Testing
0
500
1000
1500
2000
0 25 50 75 100
125
150
OSM
OTIC FLOW RAT
E -‐g
/m2
DAYS FROM START OF TEST
AVERAGE OSMOTIC FLOW THROUGH MEMBRANES #1 & #2
Membrane #1 -‐ 30 mil Aged
Membrane #2 -‐ 60 mil Aged
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0
200
400
600
800
1000
1200
1400
1600
0 20 40 60 80 100 120 140 160 180 200
Osm
oti
c Fl
ow
Rat
e -
g/m
2
# days from start of test
OSMOTIC FLOW THROUGH VARIOUS ASPHALT MODIFIED POLYURETHANE WATERPROOFING MEMBRANES
Membrane #1 - 30 mil - blistered
Membrane #1 - 30 mil - blistered
Membrane #2 - 60 mil - blistered
Membrane #3 - 70 mil - blistered
Membrane #5 - 120 mil - unknownperformance
Membrane #7 - 60 mil - unknownperformance
Membrane #9 - 100 mil - unknownperformance
Membrane #10 - 100 mil - unknownperformance
New vs Aged Membrane Testing
Aged - Blistered
New – Unknown Performance
Same membrane manuf. & chemistry
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Impacts of Primers?
0
50
100
150
200
250
300
350
400
0 20 40 60 80 100 120 140 160 180 200 220 240 260
Osm
oti
c Fl
ow
thro
ugh m
embra
ne
-g/m
2
Days from Start of Test
EFFECT OF MEMBRANE PRIMER TYPE - POLYURETHANE VS EPOXY
Epoxy Primer on membrane - 0.5 Perms
Polyurethane Primer on membrane - 0.9 Perms
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Findings – Original Membranes
à Asphalt modified polyurethane membranes have serious
shortcomings as waterproofing
à Vapor permeance typically >5 US Perms after aging, even if
initially <1 US perms
à Osmotic Flow Rates of 5-12 g/m2/day,
(up to 20+ g/m2/day with some 10-15 year old membranes)
à Aged values much worse than initial • Impacts of alkaline environment and constant wetting?
à Some primers effective at reducing flow rate, but difficult to
apply to sufficient thickness in field
à Conclusion – if we could reduce osmotic flow rate to less than
the vapor diffusion rate through concrete slab then could we
be okay?
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Summary: Osmotic Blistering Process
à Top surface of the membrane wet all
year (insulation/dirt/water feature)
à Moisture moves though the membrane
via vapor diffusion
à Concrete less permeable than the
membrane = moisture accumulation
à Moisture dissolves minerals from
concrete
à Osmosis forms small blisters at
localized voids or de-bonded areas of
membrane
à Osmotic pressure grows and continues
expanding blisters over time
Water on top of membrane almost year round in inverted roofassembly (poor slope = more water)
Concrete is initially at or close to saturation. Vapour diffusionmoves additional moisture though membrane to concreteinterface.Concrete is less permeable than membrane and water begins tosaturate the concrete and accumulate at the membraneinterface.
Mineral ions dissolve out of concrete increasing the saltconcentration of the water beneath the membrane. Osmosisbegins and small blisters are formed.
Vapour diffusion to interior through concrete is relativelyslow compared to the rate transported by Osmosis.
Blisters grow and expand due to osmotic flow.
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Worldwide Findings
à RDH observations à Pacific Northwest to California
à Reported Osmotic Blistering issues by others through
discussions and by our project involvement à Florida & Southern US
à Hawaii
à New Zealand
à Europe & Asia
à Appears more prevalent in temperate, humid climates –
where water is able to sit on membrane year-round à Or in ponds, planters and other wet places
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Added to Hartwig Kuenzel’s Roofing Book
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Lots of Repairs Made… With Other Materials Many Blistered Membrane Renewals Projects
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A Little Caution About Roofers & Tie-ins…
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New and Ongoing Research
à Between 2008 and 2014 we have worked with numerous
liquid applied membrane manufacturers to address osmosis
à Measure osmotic flow rate, vapor permeance, absorption
à Assess impacts of thickness, reinforcing, primers, fillers, cure
method, different chemistries, etc.
à Looked at alternate membrane chemistries & membrane types
• 2 component & single component chemistries • Polyurethanes (asphalt and non-asphalt modified) • Polyureas
• Polyesters • PMMAs • Asphalt Emulsions
à Continued testing of original two membrane offenders &
other membranes applied in past decade (litigation and R&D)
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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?
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0
250
500
750
1000
1250
1500
0 20 40 60 80 100 120
OSM
OT
ICF
LO
WT
HR
OU
GH
MEM
BR
AN
E, g
/m²
Days from Start of Test
VARIOUS POLYUREA MEMBRANES (7 TYPES) AVERAGED OSMOTIC FLOW RATES
What About Polyureas?
Aged asphalt modified urethane control sample
7 new different polyurea chemistries
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What About Polyureas
Membrane Sample Name
Membrane Thickness:
Average, mils
Range, mils
Osmotic Flow Rate
Average, g/m2/day
Range, g/m2/day
Water Absorption - % & Time to Reach
Equilibrium
Inverted Vapour Permeance as
Measured:
US Perms
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
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What About Other Chemistries?
What About Other Membrane Chemistries?
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What About Other Membrane Chemistries?
Membrane Sample Name
Vapour Permeance of 100 mil Standard
Thickness: (US Perms)
Water Absorption: % by Mass Osmotic Flow Rate,
Thickness
Average, g/m2/day
Wet Cup Inverted Wet Cup At 20 days At 250 days
AFU-Asphalt Free Urethane Resin
0.08 US Perms
0.08 US Perms 1.6% >4.5% (has not
stopped) ~0.7 (87 mils)
PE – Polyester Based System
0.26 US Perms
0.27 US Perms 1.3% 0.2% 0.4 (55 mils)
PE2 Two component polyester system
0.31 US Perms
0.33 US Perms 1.7% 0.8% 0.5 (54 mils)
PMMA – Poly Methyl MethAcrlyate
0.27 US Perms
0.28 US Perms 1.7% >4.4% (has not
stopped) ~0.8 (65 mils)
RED = BAD TRAIT, GREEN = DESIRABLE TRAIT, ORANGE - BORDERLINE
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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?
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Comparison of Results to Date
0
2
4
6
8
10
12
14
16
18
20
0 1 2 3 4 5 6 7 8 9 10
OSM
OT
ICF
LO
WR
AT
E-g
/m2
(ALL
SA
LT
SO
LU
TIO
NS)
Inverted Wet Cup Vapor Permeance - US Perms
INVERTED WET CUP VAPOR PERMEANCE VS OSMOTIC FLOW RATE - COMPARISON
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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0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
OSM
OT
ICF
LO
WR
AT
E-g
/m2
(ALL
SA
LT
SO
LU
TIO
NS)
Inverted Wet Cup Vapor Permeance - US Perms
INVERTED WET CUP VAPOR PERMEANCE VS OSMOTIC FLOW RATE - COMPARISON
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
Comparison of Results to Date
Targets: <0.1 US perms, <0.1 g/m2 Osmotic Rate Plus minimal absorption
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Revised Test Procedure & Targets
à Key Measurements: à Vapor Permeance – Inverted wet cup testing (<0.1 perms, want
this to be less than the concrete slab)
à Osmotic Flow Rate – measure by apparatus with control salt
solution for 3-6 months (<0.1 g/m2/day)
à Water Absorption – soak it until it stops (<1%)
Osmotic Flow Rate
Concrete Vapour Diffusion Rate
√ ? X
< = >
VS.
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Recommendations
à 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.)
à Be very careful of membranes made for “green concrete” as
tend to be worse (higher vapor permeance)
à Not just a black asphalt modified membrane problem –
affects all types – polyureas, polyurethanes, PMMAs etc.
à In meantime use a good tried and true fully adhered system –
use hot rubber, 2 Ply SBS, built-up asphalt etc.
à Where “hands-tied”, keep water from getting down to liquid
waterproofing (supplemental drainage above insulation)
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Some Conversions
à Desired Inverted Wet Cup Vapor permeance to be less than
0.1 US Perms (<6 ng/Pa s m2)
à Few manufacturers report inverted wet cup, usually just wet
cup (Procedure B) (or worse still dry cup, Procedure A)
à Inverted wet cup values typically 10 to 50% higher than wet cup
and can be many times higher than dry cup values
à Watch reporting units à 1 mil = 1/1000”
à 1 mm = 25.4 mils
à Permeability in perm-in : divide by thickness (inches)
à WVT (grains/hr/ft2) not same units or value as vapor
permeance (grains/hr/ft2 inHg)
à Convert to US perms for quick check
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Red Flags to Look Out For
2.3 US Perms!
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Red Flags to Look Out For
Withdrawn standard Needs Updating!
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Red Flags to Look out For
1.7 US Perms (DRY CUP)
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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)
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Next Steps
à Determine maximum safe vapor permeance threshold for
waterproofing membranes over concrete
à Refine and develop ASTM osmotic flow test method and determine
acceptable maximum flow rates for different applications.
à Revise Applicable Standards (ASTM C836 and/or withdrawn CAN/
CGSB–37.58-M86) to specify:
à Maximum allowable inverted wet cup permeance (<0.1 perms?)
à Maximum absorption for constant & prolonged immersion (this
is not the typical 24 hr/7day ASTM test)
à Maximum allowable osmotic flow rate (<0.1 g/m2, so less than
concrete can dry through)
à Consideration for aging and submersion within wet concrete
environment (accelerated wet alkaline test?)
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Next Steps
à Need a waterproofing industry champion to raise
awareness and push revisions to ASTM standards and
bring forth the osmosis test method à We gave been looking for a manufacturer with a cold
applied liquid membrane that works! (market advantage)
à Testing and evaluation of all products currently on
market
à Hopefully No More Problems!?
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A Final Word of Warning