Waterproofing membranes are widely used in the building industry as a barrier for water entry into a building enclosure. Over the past two decades, waterproofing system failure due to osmotic blistering has occurred in some protected membrane/inverted roofing assemblies. Not all waterproofing membrane assemblies are at risk for this process and the authors have developed a test protocol to establish the relative risk level of waterproofing membranes to osmosis. Using this protocol, the osmotic flow rate of SBS, hot rubberized asphalt, PMMA, EPDM, TPO, HDPE, polyurea, asphalt emulsion, asphalt-modified polyurethane, and various other 2-component cold applied membranes was measured to determine a threshold osmotic flow rate for low risk waterproofing membrane systems. In this research, a wide range of osmotic flow rates were obtained for the various membrane types. Most asphalt-modified polyurethane membranes consistently exhibit osmotic flow rates significantly higher than the low-risk threshold of ~0.0 g/m²/day (typically 1.4 to over 20 g/m²/day) after data corrections, which results in osmotic blistering and premature membrane failures. Some polyurea and asphalt emulsion membranes have flow rates above 2.0 g/m²/day with unknown long-term performance, while most other membranes that were tested have flow rates around 0.0 g/m²/day after data corrections from control samples. To reduce the potential for osmotic blistering over concrete, it is recommended that waterproofing membranes used in inverted roofing assemblies should have an osmotic flow rate near 0.0 g/m²/day when tested using the methodology herein, an inverted wet cup vapour permeance less than that of the substrate (i.e. <0.1 US Perms on a concrete substrate), and minimal long-term water absorption. Presented at the 15th Canadian Conference on Building Science and Technology.

1. 1
Solutions to Address Osmosis:
Blistering of Liquid Applied Waterproofing
Membranes
CCBST CONFERENCE, VANCOUVER BC
NOVEMBER 8TH 2017
ELYSE HENDERSON, MSC; GRAHAM FINCH, MASC, P.ENG; BRIAN HUBBS, P.ENG
PRESENTED BY ELYSE HENDERSON

2. 2
 Background
 Review of theories
 Current research
 Recommendations
Agenda

3. 3
Background & History

4. 4
Review of Theories
Pinholes in thin membrane Hydrostatic head from details
Vapour diffusion from inside Diffusion & capillary from outside
X X
X X

5. 5
The Osmosis Mechanism
 Requirements for osmosis to occur:
1. Semi-permeable membrane
(impermeable to Total Dissolved Solids)
2. TDS concentration differential
(higher osmotic flow rate with higher
differential) Colligative Property

6. 6
TDS and Equivalent Osmotic Pressure
Sample A Sample B Sample C
Rain water
pooled on
membrane
Total Dissolved
Salts (TDS), mg/L
17,500 13,056 3,650 7
Osmotic
Pressure, kPa
1,488 1,089 326 ~3
 Extracted from water blisters
under blistered membranes
 TDS and equivalent osmotic
pressure are elevated!

7. 7
Research Objectives
1) Determine the susceptibility of various waterproofing
membrane types to osmotic blistering
 Find true “zero” osmotic flow
2) Set test parameters and recommendations for low-risk
membranes
 e.g. osmotic flow rate, vapour permeance, absorption
3) Understand the aging effects of membranes in contact with
liquid water for long periods of time
 Changes in material properties (e.g. vapour permeance)
 Degradation of the membrane

8. 8
Project Methodology
 Osmotic flow rate testing
 Method developed by RDH

9. 9
Project Methodology
 Osmotic flow rate testing
 Method developed by RDH
 Vapour permeance testing per ASTM E-96
 Wet cup
 Inverted wet cup

10. 10
Project Methodology
 Osmotic flow rate testing
 Method developed by RDH
 Vapour permeance testing per ASTM E-96
 Wet cup
 Inverted wet cup
 Water absorption testing
 Method adapted from ASTM D-570 for prolonged time
 Water analysis
 3rd-party analytical lab
 Measure TDS concentrations and specific solutes

11. 11
Previous Osmosis Results
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 50 100 150 200 250 300
OsmoticFlow(g/m²)
Time (days)
Asphalt-modified polyurethane 1
Asphalt-modified polyurethane 2
Asphalt emulsion
Polyurea membrane
2-Component membrane
Low enough?

12. 12
Current Osmosis Results
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 50 100 150 200 250 300
OsmoticFlow(g/m²)
Time (days)
Asphalt-modified polyurethane
Hot Rubber 1-ply
Hot Rubber 2-ply
SBS (1-ply)
PMMA 1
PMMA 2
EPDM
TPO
HDPE

13. 13
TDS Dilution from Osmotic Flow
57600 57600
57100
53600
51000
52000
53000
54000
55000
56000
57000
58000
1.0 M NaCl 1.0 M NaCl
(Hot Rubber)
1.0 M NaCl
(PMMA)
1.0 M NaCl
(Asph-Mod.
Polyurethane)
Concentration(mg/L)
 Total Dissolved Solids (TDS) concentration after 8 months
 TDS is diluted in the jar that took up most water, i.e. had the
highest osmotic flow across membrane

14. 14
Osmosis Results
Membrane Type
(name or material)
Membrane
Thickness (mil)
Osmotic Flow Rate
(g/m²/day)
Asphalt-modified
polyurethane*
30 – 90 1.4 – 26.2
Asphalt emulsion 110 4.6 ±1.6
Polyurea 30 – 100 2.1 ±1.6
SBS (1-ply) 100 0.3 ±0.8
TPO 58 0.8 ±0.9
Hot rubberized asphalt (2-ply) 244 0.0 ±0.7
HDPE 52 0.0 ±0.7
PMMA 70 – 80 -0.2 ±0.8
2-Component cold-applied 40 – 90 -0.3 ±0.8
EPDM 47 -0.3 ±0.7
*Large range of membrane thicknesses and osmotic flow rates for asphalt-
modified polyurethane samples (macroscopic variations in the samples)

15. 15
Colligative Property of Osmosis, Demonstrated
1.0 M
0.5 M
0.1 M
0.0 M
1.0 M
0.1 M
0.0 M
0
200
400
600
800
1000
1200
1400
1600
1800
0 25 50 75 100 125 150 175 200 225
OsmoticFlow(g/m²)
Time (days)
Asph.-Mod. Polyurethane, 1.0M
Asph.-Mod. Polyurethane, 0.5M
Asph.-Mod. Polyurethane, 0.1M
Asph.-Mod. Polyurethane, 0.0M
Hot Rubberized Asphalt, 1.0M
Hot Rubberized Asphalt, 0.1M
Hot Rubberized Asphalt, 0.0M
Recall, osmosis
requires semi-
permeable
membrane Flow rate depends on TDS concentration
 Higher TDS = higher osmotic flow rate
 But only for semi-permeable membranes

16. 16
How Does Vapour Permeance Affect Osmosis?
 Osmotic flow rate is higher for high vapour permeance
 How does aging affect membrane permeance?
-5
0
5
10
15
20
25
30
0 100 200 300 400 500 600
OsmoticFlowRate(g/m²/day)
Inverted Wet Cup Vapour Permeance (ng/Pa-s-m²)
Aged Asphalt-modifed Polyurethane
(blistering has occurred)
Modified Polyurethane (non-asphalt)
Polyurea
New 2-component chemistries
Hot rubberized asphalt
PMMA
1-ply SBS

17. 17
Effects of Aging Membranes
 Aged asphalt-modified polyurethane = higher permeance
 Can prolonged water absorption help us understand aging?
0
5
10
15
20
25
30
0 100 200 300 400 500 600
OsmoticFlowRate(g/m²/day)
Inverted Wet Cup Vapour Permeance (ng/Pa-s-m²)
Aged Asphalt-modifed
Polyurethane (blistering has
occurred)
New Asphalt-modified
Polyurethane

18. 18
Water Absorption Results
 Some membranes do not reach equilibrium
 Unknown effects over longer time: 1 year? 5 years? 10 years?
 Asphalt-modified polyurethane absorbs the most
 Decease in mass points to membrane degradation
-2%
0%
2%
4%
6%
8%
10%
12%
14%
16%
18%
0 20 40 60 80 100 120 140 160 180 200 220 240 260
ChangeinMass(%)
Time (days)
Asphalt-modified polyurethane
Hot rubberized asphalt
SBS (1-ply)
PMMA 1
PMMA 2
EPDM
TPO
HDPE

19. 19
What is Coming Off the Membranes?
 Total Organic Carbon (TOC) points to membrane degradation
 Degrading membranes:
 Change membrane properties (vapour permeance, rigidity, etc.)
 Increase the TDS in the water blister
› Self-propagation of osmosis in susceptible membranes
0
100
200
300
400
500
600
700
TOC Calcium Potassium Silicon Sulfur
Concentration(mg/L)
Real blister water
1.0 M NaCl (Hot Rubber)
1.0 M NaCl (PMMA)
1.0 M NaCl (Asph-Mod. Polyurethane)

20. 20
What are the Solutions?
 Rules of thumb for selecting waterproofing membranes:
1. Measured osmotic flow rate near 0 g/m²/day (+/- 1)
2. Inverted wet cup vapour
permeance lower than
substrate
3. Minimal long-term water
absorption or membrane
degradation

21. 21
Questions
CONTACT THE PRESENTER
 ehenderson@rdh.com
 1-604-873-1181