Flat roof waterproofing systems based on liquid products

Flat roof waterproofing systems based on liquid products

Experimental characterization of the systems’

mechanical performance

João Luís Garcia Feiteira

Extended abstract

Supervisor: Jorge Grandão Lopes

Co-supervisor: Jorge Manuel Caliço Lopes de Brito

November 2009


1

1. Introduction

Due to the slow drainage of accumulated rainwater, flat roofs require a waterproof coating [1].

Traditionally, for more than 100 years, this coating has been made of bituminous material

applied either as a built-up roofing system or as a membrane sheet. However, other

waterproofing materials have been available for decades.

Liquid applied roof waterproofing systems (LARWSs) include, in addition to bituminous systems,

systems based on less well-known waterproofing materials such as polyester, polyurethane and

water dispersible polymers.

LARWSs offer some advantages over membrane sheets. Applied like paint or with the help of a

spatula, they form an adhesive, seamless waterproof coating over practically any surface or

shape. Thus, both the possibility of water migrating beneath the coating and the need to treat

laps and seams are eliminated [2].

LARWS requirements and their methods of verification are established by the European

Organization for Technical Approvals (EOTA). Resistance to mechanical damage, especially

perforation, is one of the most important requirements set out in the relevant EOTA guide, the

ETAG 005 [3]. ETAG 005 also links LARWS resistance to perforation to the recommended

accessibility and frequency of traffic envisaged for the roof on which it is to be applied.

The scope of this study includes determining LARWS resistance to static and dynamic

indentations, tensile properties, fitness for intended use and flexibility at low temperature.

2. Materials and method

Free-standing samples were prepared from some of the LARWSs available on the Portuguese

market. In order to evaluate the influence of the number of coats and reinforcements on

mechanical resistance, in the case of most systems samples were obtained from different

formulations, as shown in Table 2.1. All the samples were prepared according to the

manufacturer’s instructions and dried under the conditions specified in ETAG 005, at a

temperature of 23 ºC and relative humidity of 50%. The reinforcement layers used (Table 2.2)

were as prescribed by each LARWS manufacturer.

Systems of different materials with similar thicknesses immediately after installation do not

necessarily produce coatings with similar thicknesses after drying. Thus, although desirable,

similar film thicknesses for comparable coatings could not be assured. The number of coats

(applying the quantity per coat prescribed by the manufacturer) was used instead to generate

comparable coatings and their thickness was determined by means of a digital comparator with

a 6 mm diameter cylindrical tip, so that stable readings could be obtained.

Extended abstract

2

Table 2.1 – LARWSs tested

Material Mass per

unit volume (g/cm3)

Reinforcement layer

Number of coats

Total quantity (kg/m2)

Minimum drying time

(days)

Mean dry sample

thickness (mm)

- 2 3,47 2.32 2 4,56 2.43 Two-

component cementitious

1.35 Fibreglass mat (4 mm mesh; 200

g/m2) 3 6,33 21

3.62

- 2 2,93 1.50 2 3,61 1.23 Acrylic 1.45 Fibreglass mat (2

mm mesh; 60 g/m2) 3 4,38

21 1.80

2 2,66 1.21 Fibrous acrylic 1.40 - 3 4,09 21 1.91 Partially

bonded two-component

cementitious

1.45 Unidentified fleece (90 g/m2) 2 2,18 21 1.62

- 2 2,70 1.44 2 2,52 1 1.52 Liquid silicone 1.3 Polyester fleece

(50 g/m2) 3 3,93 2 2.38 - 2 0,99 0.72

2 0.97 0.67 Liquid rubber 1.2 Polyester fleece (50 g/m2) 3 1,45

4 1.00

Polyurethane 1.43 - 2 2,74 5 1.37

Table 2.2 – Reinforcement layers used

Reinforcement layer Mass per unit area (g/m2)

Maximum tensile force

(N/50 mm)

Elongation at maximum tensile

force (%) Fibreglass mat (2 mm mesh) 60 660 3 Fibreglass mat (4 mm mesh) 200 1935 4

Unidentified fleece 90 110 50 Polyester fleece 50 150 22

Each system was tested for the following properties:

watertightness, using the method described in the EOTA Technical Report (TR) 003

[4]; a 1m hydrostatic head of water was applied to the exposed side of the test

specimens and, after a period of 24 h, these were inspected for signs of leakage;

resistance to dynamic indentation (impact) according to TR 006 [5]; this method

requires a fixed impact energy of 5.9 J to be applied to LARWS test specimens by

means of a cylindrical steel indentor with a given diameter; each diameter being

linked to a level of performance, as shown in Table 2.4;

resistance to dynamic indentation (impact) according to EN 12691 [6]; this method

was used to further differentiate between resistance to this type of mechanical

damage in the LARWSs being tested; in this case, test specimens were struck by a

drop mass of 500 g using a 12.7 mm diameter spherical puncturing tool;

resistance to static indentation (impact) according to TR 007 [7]; a load is applied to

a 10 mm steel rod with a hemispherical end resting on the exposed side of the test


3

specimen; each of the four defined loads is linked to a level of performance, as

shown in Table 2.5;

tensile properties according to EN 12311-1 [8]; test specimens are clamped in the

grips of a tensile testing machine capable of maintaining a uniform rate of

separation and the values for the maximum tensile force and corresponding

elongation are registered;

flexibility at low temperature according to EN 1109 [9]; after being kept at 5 ºC for 1

h, test specimens were bent over a cylindrical shape with a diameter of 30 mm until

a 180º angle was reached between the ends of the specimens; after being bent, the

test specimens were visually inspected for cracking.

Table 2.3 shows the number of test specimens per system used in each test. For dynamic

indentation tests made according to TR 006, only 3 of the 5 specimens assigned to dynamic

indentation were used. For reinforced coatings, EN 12311-1 requires that 10 specimens be

tested; 5 of them taken from the longitudinal direction of the reinforcement layer and the other 5

from the transverse direction.

Table 2.3 – Number of test specimens

Test Number of specimens Dimensions (mm) Watertightness 3 200 x 200

Dynamic indentation 5 200 x 200 Static indentation 3 200 x 200

Tensile properties – unreinforced system 5 300 x 50 Tensile properties – reinforced system 5 + 5 300 x 50

As prescribed in ETAG 005, each LARWS should be included in one of four user load

categories, defined in Table 2.6, with a corresponding recommended accessibility and

frequency of traffic envisaged for the roof on which it is to be installed.

It should be noted that absolute categorisation of a LARWS according to user load requires

further testing of its resistance to ageing media and the effects of low and high surface

temperatures. In addition, as all the tests were carried out on free-standing test specimens, the

influence of substrate adhesion on the coating’s resistance to perforation was not taken into

account.

Table 2.4 – Levels of resistance to dynamic indentation

Level of resistance I4 I3 I2 I1 Diameter of indentor (mm) 6 ± 0.05 10 ± 0.05 20 ± 0.05 30 ± 0.05

Table 2.5 – Levels of resistance to static indentation

Level of resistance L1 L2 L3 L4 Load (N) 70 ± 1 150 ± 1 200 ± 1 250 ± 1

Extended abstract

4

Table 2.6 – Relationship between user load category and indentation levels of resistance

Minimum level of resistance User load category Dynamic indentation Static indentation Examples of accessibility

P1 I1 L1 Non-accessible

P2 I2 L2 Accessible for maintenance of the roof only

P3 I3 L3 Accessible for maintenance and to pedestrian traffic

P4 I4 L4 Roof gardens, inverted roofs, green roofs

3. Results and discussion

3.1. Watertightness After 24 h, only the 2-coat reinforced liquid rubber based coating showed signs of leakage. The

fact that the unreinforced and the 3-coat reinforced liquid rubber based coatings remained

watertight during the test shows that this was caused by not using a sufficient amount of

waterproofing material to cover the fleece used as reinforcement.

When dealing with a LARWS with a low recommended quantity per coat (less than 1 kg/m2),

care must be taken that, if used, the reinforcement layer is adequately covered.

As it did not satisfy the essential requirement of a waterproofing coating – that it should be

waterproof - no further tests were done on the 2-coat reinforced liquid rubber based coating. All

the other coatings tested were considered watertight.

3.2. Resistance to dynamic indentation The results (Table 3.1) show that resistance to impact in all the systems complies with their

intended use. All but the silicone based systems reached the highest level of resistance

prescribed in ETAG 005.

The test method described in EN 12691 allowed for further differentiation of resistance to this

kind of mechanical damage.

Figure 3.1 shows the performance of comparable unreinforced coatings based on 2 coats of

different materials. Even though most coatings reached the highest resistance level when tested

under the TR 006 method, in this case the results revealed a distinct performance gap between

systems of different materials.

While the performance of acrylic, cementitious and polyurethane based coatings was similar,

the fibrous acrylic coating showed a significant (50%) relative decrease in resistance to dynamic

indentation. There was also evidence of a much higher susceptibility to perforation in liquid

silicone and liquid rubber based coatings, when compared to all the other coatings tested.

The fact that the 2-coat unreinforced cementitious coating had a significantly higher film

thickness than all the other unreinforced coatings has to be taken into account when judging its

performance. The same resistance to impact (0.70 m) was achieved by acrylic and

polyurethane based coatings with much lower thicknesses.


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Table 3.1 – Resistance to dynamic indentation test results

Material Reinforcement layer Number of coats

Minimum diameter of

indentor (mm)

Maximum drop height

(m) - 2 6 0.70

2 6 1.00 Two-component cementitious Fibreglass mat (4 mm

mesh; 200 g/m2) 3 6 ≥ 2.00 - 2 6 0.70

2 6 0.60 Acrylic Fibreglass mat (2 mm mesh; 60 g/m2) 3 6 0.90

2 6 0.35 Fibrous acrylic - 3 6 0.90 Partially bonded two-


Unidentified fleece (90 g/m2) 2 6 0.50

- 2 10 0.05 2 10 0.10 Liquid silicone Polyester fleece (50

g/m2) 3 10 0.10 - 2 6 0.15

2 - - Liquid rubber Polyester fleece (50 g/m2) 3 6 0.30

Polyurethane - 2 6 0.70

- Test not performed

0

0,2

0,4

0,6

0,8

Acrylic

Fibrous acry

lic

Cementitious

Liquid silico

ne

Liquid rubber

Polyurethane

Max

imum

dro

p he

ight

(m)

Figure 3.1 – Resistance to dynamic indentation test results for 2 coats of unreinforced LARWS

0

0,5

1

1,5

2

Reinforcedacrylic

Unreinforcedfibrous acrylic

Reinforcedcementitious

Reinforcedliquid silicone

Max

imum

dro

p he

ight

(m)

2 coats3 coats

Figure 3.2 – Resistance to dynamic indentation test results for 2 and 3-coat LARWSs

Extended abstract

6

Comparison between 2 and 3-coat based coatings (Figure 3.2) shows that, as expected, a

greater film thickness can lead to greater resistance to impact. The results also showed that this

parameter was most influential in resistance to impact in fibrous acrylic and cementitious

coatings, which, incidentally, were the stiffer materials. The 3-coat reinforced cementitious

coating reached the 2 m maximum drop height of the testing machine.

The use of a reinforcement layer led to greater resistance to impact in 2-coat cementitious and

liquid silicone based coatings. With the acrylic coating, reinforcement lead to a 0.10 m decrease

in resistance. This was linked to the lower thickness of the 2-coat reinforced acrylic sample,

when compared with the unreinforced sample.

3.3. Resistance to static indentation Static indentation tests confirmed the greater resistance to perforation in the cementitious and

polyurethane based coatings, as shown in Table 3.2. The results also showed a significant

performance gap between dynamic and static indentation resistance in acrylic coatings. While

acrylic coatings had a similar dynamic indentation resistance to cementitious and polyurethane

based coatings, only the fibrous type of this coating reached the minimum static indentation

resistance requirement prescribed in ETAG 005. Out of all the other coatings tested, only the

reinforced silicone based coatings reached the minimum level of resistance, which confirmed a

high susceptibility to perforation in liquid silicone and liquid rubber based coatings.

Table 3.2 – Resistance to static indentation test results

Maximum resistance level (N) Material Reinforcement layer Number of

coats 70 N

150 N

200 N

250 N

- 2 ● 2 ● Two-component

cementitious Fibreglass mat (4 mm mesh; 200 g/m2) 3 ●

- 2 X 2 X Acrylic Fibreglass mat (2 mm mesh;

60 g/m2) 3 X 2 ● Fibrous acrylic - 3 ●

Partially bonded two-component

cementitious Unidentified fleece (90 g/m2) 2 ●

- 2 X 2 ● Liquid silicone Polyester fleece (50 g/m2) 3 ●

- 2 X 2 - Liquid rubber Polyester fleece (50 g/m2) 3 X

Polyurethane - 2 ●

● Maximum resistance level X Coating did not reach minimum resistance level - Test not performed


7

An extra coat had no significant influence on resistance to this type of mechanical damage.

None of the 3-coat reinforced coatings tested reached a higher level of resistance than the

corresponding 2-coat reinforced coatings.

The use of a reinforcement layer allowed all the 2-coat coatings to reach one higher level of

resistance and thus had a clear influence on LARWS performance in terms of static indentation.

3.4. Tensile properties Tensile test results (Table 3.3) confirmed what had already been expected from handling test

specimens of different LARWSs.

Unreinforced liquid silicone and polyurethane based coatings were much more deformable than

all the other coatings tested, as shown in Figure 3.3, with the latter being much stiffer. The

elongation values were limited to 200%, the maximum course of the tensile testing machine.

Out of all the other unreinforced coatings, the acrylic coating was still considerably more

deformable, the fibrous acrylic coating was the stiffest and the liquid rubber based coating had

the least resistance of all.

Table 3.3 – Tensile properties of LARWSs tested

Maximum tensile force (N/50 mm)

Elongation at maximum tensile force (%) Material Reinforcement

layer Number of coats Mean value Standard

deviation Mean value

Standard deviation

- 2 75 7 25 5 2 1855 290 5 0 Two-


Fibreglass mat (4 mm mesh;

200 g/m2) 3 2145 152 5 0

- 2 80 10 87 7 2 795 52 4 0 Acrylic Fibreglass mat

(2 mm mesh; 60 g/m2) 3 935 57 5 0

2 160 12 12 1 Fibrous acrylic - 3 295 17 13 1

Partially bonded two-component

cementitious

Unidentified fleece (90

g/m2) 2 385 8 49 1

- 2 ≥35 * ≥196 * 2 220 29 31 6 Liquid

silicone Polyester fleece (50

g/m2) 3 270 21 40 2

- 2 35 3 25 9 2 - - - - Liquid rubber Polyester

fleece (50 g/m2) 3 240 16 36 1

Polyurethane - 2 ≥225 * ≥196 *

* Not calculated due to reaching maximum tensile testing course of machine - Test not performed

Extended abstract

8

0

50

100

150

200

250

Acrylic

Fibrous Acry

lic

Cementitious

Liquid silico

ne

Liquid rubber

Polyurethane

0%

40%

80%

120%

160%

200%

Maximum tensile force (N/50mm) Elongation at maximum tensile force (%)

Figure 3.3 – Tensile properties of 2- coat unreinforced LARWSs

Resistance to perforation in a given coating cannot be explained solely by its deformability or

stiffness, but should depend also on other intrinsic properties of each material. Although both

were highly deformable, there was a significant performance gap between the liquid silicone

and polyurethane based coatings when tested for resistance to perforation. Moreover, stiffness

cannot, in itself, account for a coating’s higher resistance to this type of mechanical damage.

Even though the fibrous acrylic coating was stiffer than all the other coatings tested, the results

showed it had significantly lower resistance to perforation than both the cementitious and

polyurethane based coatings.

Figure 3.4 shows the force-strain curves for one of the test specimens of each of the

unreinforced coatings, becoming clearer that the fibrous acrylic coating is the stiffest of all.

0

50

100

150

200

250

0% 50% 100% 150% 200%Elongation (%)

Forc

e (N

)

CementitiousAcrylicFibrous acrylicLiquid siliconeLiquid rubberPolyurethane

Figure 3.4 – Force-strain curves of the unreinforced coatings.

When reinforced, all coatings showed similar tensile properties to those of the corresponding

reinforcement layer (Table 2.2). An additional coat had no significant influence on the tensile


9

properties of any of the reinforced coatings tested, but allowed for an 85% increase in the

maximum tensile force of unreinforced fibrous acrylic coating.

3.5. Flexibility at low temperature All unreinforced coatings except the unreinforced acrylic coating were submitted to a flexibility at

low temperature test. None of them showed signs of cracking and only the liquid rubber coating

became considerably stiffer.

3.6. User load category Table 3.4 shows the user load category of all the LARWSs tested, according to ETAG 005. For

all LARWSs, resistance to static indentation determined their user load category.

Table 3.4 – User load category of LARWSs tested

Resistance level Material Reinforcement

layer Number of coats Dynamic

indentation Static

indentation

User load category

- 2 I4 L3 P3 2 I4 L4 P4 Two-component

cementitious Fibreglass mat (4 mm mesh;

200 g/m2) 3 I4 L4 P4

- 2 I4 X X 2 I4 X X Acrylic Fibreglass mat

(2 mm mesh; 60 g/m2) 3 I4 X X

2 I4 L1 P1 Fibrous acrylic - 3 I4 L1 P1 Partially bonded two-


Unidentified fleece (90 g/m2) 2 I4 L4 P4

- 2 I3 X X 2 I3 L1 P1 Liquid silicone Polyester fleece

(50 g/m2) 3 I3 L1 P1 - 2 I4 X X

2 - - - Liquid rubber Polyester fleece (50 g/m2) 3 I4 X X

Polyurethane - 2 I4 L4 P4

X Coating did not reach minimum resistance level - Test not performed

The acrylic and liquid rubber based LARWSs tested should not be used on any kind of flat roof

due to their high susceptibility to perforation by punctual static loads.

Out of all the LARWSs tested, only cementitious (reinforced or unreinforced) and polyurethane

based LARWSs should be used on roofs designed for pedestrian traffic.

In addition to cementitious and polyurethane based LARWSs, fibrous acrylic LARWSs were the

only unreinforced systems suitable for use on flat roofs, but only of the non-accessible kind.

Liquid silicone based LARWSs should only be installed on flat roofs if reinforced and, even then,

only on non-accessible roofs.

Extended abstract

10

4. Conclusions

This study revealed significant mechanical performance differences between several available

LARWSs.

Cementitious, acrylic and polyurethane based coatings had a much higher resistance to

dynamic indentation than all the other coatings tested, including liquid silicone and liquid rubber

coatings. The results also showed a significant performance gap between coatings of different

materials after testing for resistance to static indentation. In this case, only cementitious and

polyurethane based coatings showed a resistance to punctual static loads that was clearly fit for

their intended use.

The use of a reinforcement layer yielded higher resistance to both dynamic and static

indentations, while an extra coat only led to a significant increase in the former.

The use of a reinforcement layer also changed LARWS tensile properties. The tensile

properties of reinforced coatings were similar to those of the corresponding reinforcement layer.

Tensile tests also showed that deformability and stiffness cannot, in themselves, account for the

significant performance differences between coatings of different materials.

In accordance with ETAG 005, the results of the dynamic and static indentation tests showed

that cementitious and polyurethane LARWSs are fit for use on flat roofs accessible to

pedestrian traffic. Due to their susceptibility to perforation by static punctual loads, the acrylic,

liquid silicone and liquid rubber LARWSs tested were, at best, fit for non-accessible roofs.

Further investigation is needed in order to determine the effect of ageing media, extreme

surface temperatures and substrate adhesion on resistance to perforation in each coating.

Bibliography

[1] GRANDÃO LOPES, Jorge M. - Flat roof waterproofing coatings. ITE 34. Lisbon, LNEC,

1994.

[2] ALLENSTEIN, Paul - Global roofing trends going green: cold-liquid-applied membranes offer

earth-friendly product. Interface, technical journal, Vol. XXV, No. 9. Raleigh, North Carolina,

October 2007, pp. 32-36.

[3] European organization for technical approvals (EOTA) - ETAG 005 - Guideline for European

technical approval of liquid applied roof waterproofing kits. Brussels, 2004.

[4] European organization for technical approvals (EOTA) - TR 003 - Determination of the

watertightness. Brussels, 2004.


resistance to dynamic indentation. Brussels, 2004.


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[6] Comité Européen de normalisation (CEN) - Flexible sheets for waterproofing - Bitumen,

plastic and rubber sheets for roof waterproofing - Determination of resistance to impact, NP EN

12691. Brussels, 2008.


resistance to static indentation. Brussels, 2004.

[8] Comité Européen de normalisation (CEN) - Flexible sheets for waterproofing - Part 1 -

bitumen sheets for roof waterproofing - Determination of tensile properties, EN 12311-1.

Brussels, 1999.

[9] Comité Européen de normalisation (CEN) - Flexible sheets for waterproofing - Part 1 -

bitumen sheets for roof waterproofing - Determination of flexibility at low temperature, EN 1109.

Brussels, 1999.

Documents

Flat roof waterproofing systems based on liquid products