Rehabilitation of waterproofing coatings in flat roofs ...€¦ · Rehabilitation of waterproofing...

Rehabilitation of waterproofing coatings in flat roofs

with liquid applied products

- Extended Abstract -

Carlos André Pardal Leandro Quaresma

Supervisors

Researcher Jorge Manuel Grandão Lopes

Professor João Pedro Ramôa Ribeiro Correia

October 2015

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1. Introduction

A flat roof system is made of several elements, each one with its own function, the waterproofing

coating being one the most relevant. Indeed, its correct performance prevents the water ingress

to the underlying layers, thus contributing for the protection of the structure and to maintain its

habitability conditions and/or its functionality.

Since this kind of roofing is very common in Portugal [1], it is of the utmost importance to study

the most frequent anomalies in the waterproofing coatings, their main causes and possible

repairing and rehabilitation solutions. The causes for the most frequent anomalies in flat roof’s

waterproofing coatings can be divided into the following groups: design errors, application errors,

external mechanical actions, environmental actions and lack of maintenance. The most common

repairing solutions comprise the complete replacement of the waterproofing coating or the

application of the same type of material in a limited and well defined area.

A recent alternative consists of applying liquid applied waterproofing products over the area that

needs to be repaired. Liquid applied waterproofing products currently existing in the market, due

to their mechanical, physical and chemical properties, can be considered as a potential solution

for the above mentioned purpose. However, to the best of the author’s knowledge, there is no

information available in the literature about the performance of this repair strategy.

The main goal of this dissertation is thus to evaluate the suitability of liquid applied waterproofing

products for the repair of waterproofing coatings made of prefabricated membranes. For this

study, the mechanical actions on the waterproofing coatings are considered as the most

important. Therefore, an experimental campaign was prepared, in which the performance of

overlapping joints between the several prefabricated waterproofing membranes and the several

liquid applied products was studied through shear and peeling tests. It was decided to include in

this study the most relevant materials existent in the market, both for the prefabricated

waterproofing membranes (oxidized bitumen, APP polymer bitumen, SBS polymer bitumen and

PVC) [2] and for the liquid applied waterproofing products (fibrous acrylic, liquid rubber, bi-

component cementitious, polyurethane and liquid silicone). As mentioned, the topic of this

investigation is currently underdeveloped and there is no regulatory documentation applicable to

this specific repair approach; therefore, in the performed tests it was necessary to use and adapt

the European standards and directives applicable to prefabricated waterproofing coatings.

2. Experimental programme

2.1. Objectives

The experimental campaign described below was developed in order to achieve the goals

established for the present dissertation. These goals are, essentially, the characterization and the

evaluation of the overlapping joints quality between new flexible prefabricated waterproofing

sheets and liquid applied waterproofing products, in order to determine the suitability of the latter

for the repair and rehabilitation of waterproofing systems composed by the former.

Due to the lack of regulatory documentation applicable to the specific subject of this dissertation,

an extensive and careful review of the technical literature was performed, namely about the

materials involved in the experimental campaign. After selecting the materials to be used, the

respective manufacturers were contacted and requested to provide the samples needed to

perform the tests, both for the prefabricated membranes and the liquid applied waterproofing

materials; for the latter, suppliers were also asked to indicate a representative to correctly apply

their products. Alongside the main experimental campaign, oriented towards the understanding

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of the behavior of the overlapping joints, and consisting of shear and peeling tests,

complementary tensile tests were also performed in all the materials involved, allowing gathering

more experimental information of great importance for this dissertation’s conclusions. As

mentioned above, since at present there is no regulatory documentation applicable to the specific

type of repair operations investigated in this dissertation, namely regarding the performance of

mechanical tests with liquid applied waterproofing products, it was necessary to adopt the same

type of documentation applicable to flexible prefabricated waterproofing membranes.

2.2. Materials

Since the main subject of this dissertation is the characterization and evaluation of the

performance of overlapping joints between flexible prefabricated waterproofing sheets and liquid

applied products, there was no need to set certain common parameters. One decided to choose

solutions as resistant as possible, according to the manufacturers’ indications, mainly regarding

the reinforcement, the mechanical characteristics and the products application quality. Another

factor for the choice of the several materials was their significance in the market.

The selected membranes for this study, as well as their main characteristics, are described in

Table 1. The choice for the polyester felt reinforcement was due to the fact that this solution

presents, when compared to glass fiber reinforcement and for similar conditions and dimensions,

higher extension capacity under tensile stresses.

Table 1 – Prefabricated membranes and their main characteristics.

Membrane Mass

(kg/m2) Width (mm)

Reinforcement Finishing

Oxidized bitumen

4.0 2.5 Polyester felt Polyethylene film

APP polymer bitumen


SBS polymer bitumen


PVC 1.5 1.2 Polyester felt -

The liquid applied waterproofing products, used in this study, are presented in Table 2, together

with their main characteristics, as per the respective manufacturers. Concerning the application

conditions and techniques, storing and curing processes, all manufacturers’ recommendations

were followed. Also in this case the most resistant solutions were selected and whenever possible

the polyester felt reinforcement was incorporated. However, in two products, according to

manufacturer’s suggestion, the glass fiber reinforcement was used and in two other products

there was no reinforcement at all, as this is the usual application process in a jobsite.

The systems tested to assess the performance of the overlapping joints resulted from the

combination between all the liquid applied waterproofing products and all the new prefabricated

waterproofing membranes.

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Table 2 – Liquid applied products and their main characteristics.

Product Consumption

(kg/m2) Width (mm)

Reinforcement Base Curing (days)

Fibrous acrylic 3.0 2.0 Glass fiber Aqueous 21

Liquid rubber 1.2 1.0 - Solvent 1

Bi-component cementitious

3.6 2.0 Polyester felt Aqueous 21

Polyurethane 2.2 2.0 Glass fiber Solvent 7

Liquid silicone 2.5 2.0 - Aqueous 1

2.3. Equipment

For the determination of the mechanical properties of the materials and the overlapping joints, a

universal mechanical testing machine, with a 5 kN capacity load cell, was used. Two metallic jaws

were attached to both edges of the machine, as illustrated in Figure 1.

Figure 1 – Universal mechanical testing machine.

2.4. Test procedures

For the collection of samples of bituminous and plastic membranes the NP EN 13416 [3] standard

was used, that defines the sampling procedures for this kind of membranes. For all mechanical

tests performed, the specimens were cut from the membranes’ longitudinal direction.

For the products’ application it was necessary to previously prepare special devices that are

depicted in Figure 2. The applications were all performed by specialized technicians from each of

the manufacturers in order to guarantee its best quality. For those applications different tools were

used, such as trowels, paint rollers and brushes.

a)

b)

c)

Figure 2 – Application devices for: a) tensile tests; b) shear tests; and c) peeling tests.

4

All products were applied in two coatings with a 24 h period between them, with the exception of

the fibrous acrylic, where a 48 h period was needed, as per manufacturer’s indication. With the

exception of the liquid rubber, with a 1 mm width, all products were applied in order to achieve a

final width of 2 mm.

For the tensile test, the prefabricated membranes and the liquid applied product specimens were

obtained as per the NP EN 12311-1 [4] and the EN 12311-2 [5] standards. For the shear test, the

specimens were cut as per the NP EN 12317-1 [6] and the EN 12317-2 [7] standards, for the

bituminous membranes and the PVC membrane, respectively. Regarding the peeling test, the

standards used were the NP EN 12316-1 [8] and the EN 12316-2 [9] for the bituminous and the

PVC membranes, respectively. Figure 3 illustrates, as an example, the different stages of the

peeling test specimen manufacturing process.

a)

b)

c)

Figure 3 – Different stages of the peeling test specimen manufacturing process: a) application;

b) cutting; and c) final specimen.

After the gathering of all the specimens for the several kinds of tests, they were properly

conditioned in a ventilated room until the tests were performed.

For the development of the tests the specimens were introduced in the universal mechanical

testing machine, installed in a heat-controlled room, as per the specific standards. The tests were

completely monitored by a computer connected to the machine and the force and the elongation

values were registered. The tests were carried-out until the complete failure of the specimen and

the failure mode of each specimen was properly registered.

3. Results and discussion

3.1. Mechanical performance of materials

3.1.1. Prefabricated membranes

Figure 4 presents a summary of the tensile tests performed on prefabricated membranes in terms

of their maximum load. The results obtained show that the membrane that presents higher

resistance is the PVC one. Regarding the bituminous membranes, the oxidized bitumen is the

one that has the highest tensile strength value, followed by the APP polymer bitumen membrane

and by the SBS polymer bitumen membrane, wherein these last two present similar values.

Figure 5 shows the failure modes obtained for the different prefabricated membranes, when

subjected to the tensile test.

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Figure 4 – Maximum tensile force (standard deviation as error bars) of the prefabricated

membranes.

a)

b)

c)

d)

Figure 5 – Failure modes for prefabricated membranes: a) Oxidized bitumen; b) APP polymer

bitumen; c) SBS polymer bitumen; and d) PVC.

Comparing these results to those obtained by António [10], it appears that the only membrane

whose results present the same order of magnitude is the APP polymer bitumen, and this is due

to the fact that in both studies this membrane incorporates a polyester felt reinforcement.

Regarding the remaining membranes, the resistance values obtained are significantly higher than

the ones obtained by António [10], since in this study membranes with glass fiber reinforcement

were used, unlike the ones in this dissertation, which incorporate polyester felt reinforcements.

0

200

400

600

800

1000

1200

1400

OXI BIT APP SBS PVC

Ten

sile

max

imu

m f

orc

e (

N)

6

3.1.2. Liquid applied products

Figure 6 presents the maximum tensile force measured in the different liquid applied

waterproofing products. It can be seen that the one with the highest tensile resistance was, by

far, the bi-component cementitious system, followed by the polyurethane, the fibrous acrylic and,

for substantially lower values, the liquid silicone and the liquid rubber. The significant variation

between the obtained values for the bi-component cementitious and the other products is due to

the fact that the bi-component cementitious was reinforced with polyester felt, in contrast with the

fibrous acrylic and the polyurethane that were reinforced with glass fiber. The liquid silicone and

the liquid rubber were applied with no reinforcement. It is worthy to note that the decision of

applying reinforcement or not and its typology was defined according to the manufacturers’

indications.

Figure 6 – Maximum tensile force (standard deviation as error bars) for the liquid applied products.

Figure 7 shows the failure modes obtained for the different liquid applied products, when

subjected to the tensile test.

Comparing the results obtained here with the ones reported by Feiteria [11], it can be concluded

that, for the same application and reinforcement conditions, the values’ orders of magnitude are

similar for all the tested products.

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Fibrous acrylic Liquid rubber Bi-componentcementitious

Polyurethane Liquid silicone

Ten

sile

max

imu

m f

orc

e (

N)

7

a)

b)

c)

d)

e)

Figure 7 – Failure modes for liquid applied products: a) fibrous acrylic; b) liquid rubber; c) bi-

component cementitious; d) polyurethane; and e) liquid silicone.

Table 3 presents a summary of the mechanical characteristics obtained in the tensile tests for all

the materials and the respective UEAtc technical guides’ requirements verification.

Table 3 – Mechanical characteristics obtained from the tensile tests for the prefabricated

membranes and for the liquid applied products.

Membrane / liquid product Tensile maximum

force (N)

Elongation in the maximum force

(mm)

UEAtc requirements verification

Oxidized bitumen 861.25 ± 44.7 76.89 ± 2.7 Yes

APP polymer bitumen 743.87 ± 78.0 91.85 ± 7.7 Yes

SBS polymer bitumen 736.22 ± 121.3 94.85 ± 5.7 Yes

PVC 1228.53 ± 85.7 46.37 ± 4.4 Yes

Fibrous acrylic 185.78 ± 18.1 21.21 ± 2.8 ---

Liquid rubber 20.50 ± 0.9 51.07 ± 4.1 ---

Bi-component cementitious 1723.56 ± 96.3 10.94 ± 0.7 ---

Polyurethane 447.34 ± 72.5 9.74 ± 0.8 ---

Liquid silicone 58.31 ± 5.3 219.39 ± 20.9 ---

3.2. Mechanical performance of overlapping joints

3.2.1. Shear tests

In the shear tests, it was found that, in general, with the exception of the bi-component

cementitious product, all the liquid applied products presented failure modes in the repair (liquid)

product itself, therefore not being possible to mobilize the maximum resistance capacity of the

overlapping joint. In the cases of the fibrous acrylic and of the polyurethane, given the UEAtc

technical guides [12, 13], it was considered that the joint’s mechanical performance was

satisfactory, since the minimum requirements were fulfilled. For the liquid rubber and for the liquid

silicone, although failure occurred outside the joint, it was not possible to determine the joints’

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performance, since the maximum force values were too low. Regarding the bi-component

cementitious specimens, these broke in the overlapping joint, given the minimum requirements

set by the UEAtc technical guides [12, 13], it was considered that the quality of their joints is

satisfactory when connected to the oxidized bitumen and the APP polymer bitumen membranes,

while when connected to the SBS polymer bitumen and the PVC membranes they were

unsatisfactory.

Figure 8 summarizes the maximum shear force obtained for the several liquid applied

waterproofing products, when connected to the several prefabricated waterproofing membranes.

Analyzing the graphic it is possible to verify that the products that are capable of mobilizing higher

resistance, regardless of the failure location (in the joint or in the repair product), were the bi-

component cementitious and the polyurethane, followed by the fibrous acrylic, the liquid silicone

and, finally, the liquid rubber.

Figure 8 – Shear maximum force.

It can also be seen that, with the exception to the bi-component cementitious, for each liquid

applied product the shear test specimens’ failure occurred for values of the same magnitude as

the ones registered in the respective tensile test. For the bi-component cementitious product, it

was found that the maximum shear force in the overlapping joint was significantly lower than the

tensile resistance of the product.

Still analyzing figure 8, it is possible to infer that, for the only liquid applied product whose failure

occurred in the overlapping joint, the bi-component cementitious, its bonding to the prefabricated

membranes is better with the oxidized bitumen, followed the PVC and the APP polymer bitumen

membranes and, finally, by the SBS polymer bitumen membrane.

Figure 9 illustrates some examples of the failure modes obtained in the shear tests.

0

100

200

300

400

500

600

700

800

900

Oxi Bit APP SBS PVC

She

ar m

axim

um

fo

rce

(N

)

Fibrous acrylic

Liquid rubber


Polyurethane

Liquid silicone

9

a)

b)

c)

Figure 9 – Different failure modes in the shear tests; a) oxidized bitumen with bi-component

cementitious; b) APP polymer bitumen with liquid rubber; and c) PVC with polyurethane.

3.2.2. Peeling tests

The peeling tests’ results for the prefabricated membranes and liquid applied products specimens

showed that, with the exception of two distinct cases, all specimens failed at the overlapping joint

and for very low force values, causing the joints mechanical performance to be considered as

unsatisfactory, according to the minimum requirements set by the UEAtc technical guides [12,

13]. The referred exceptions were the liquid rubber connected with all the prefabricated

membranes studied and the fibrous acrylic product when connected to the PVC plastic

membrane. For the liquid rubber, even though the failure mode occurred in the repair product, the

reduced force values obtained make the performance of the joints to be classified as

unsatisfactory as well. Regarding the fibrous acrylic, it was found that when connected to the PVC

membrane, the specimens failed in the repair product close to the overlapping joint, which means

outside the joint. Despite this fact, since the obtained force values do not meet the minimum

requirements set by the UEAtc guides [12, 13], the quality of the joint was considered as not

satisfactory.

Figures 10 and 11 present respectively the specimens’ peeling maximum force and peeling

medium force for all the liquid applied products connected to all the prefabricated membranes. It

can be seen that for the bituminous membranes the values are too low, which means a weak

bonding performance, with the exception of the liquid rubber, for which the same conclusions do

not apply. Regarding the peeling tests performed over the PVC membrane, it was found that for

the fibrous acrylic, for the polyurethane and for the liquid silicone the peeling maximum force

values are significantly higher when compared with the other membranes, even though they are

also very low.

Comparatively, it is shown that, with the exception of the connection with the SBS polymer

bitumen membrane (to whom the polyurethane shows the best bonding performance), it is the

fibrous acrylic product that presents the best bonding performance to the prefabricated

membranes, followed by the polyurethane, the bi-component cementitious and, finally, the liquid

silicone, even though this last repair product presents a better bond to the PVC than the previous.

Regarding the liquid rubber, as mentioned before, given the low force values obtained, since the

overlapping joint resistance was not mobilized, it is not possible to make any comparison.

Figure 12 illustrates some examples of the failure modes obtained in the peeling tests.

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Figure 10 – Peeling maximum force.

Figure 11 – Peeling medium force.

a) b) c)

Figure 12 – Different failure modes in the peeling tests; a) oxidized bitumen with fibrous acrylic;

b) SBS polymer bitumen with liquid silicone; and c) PVC with liquid rubber.

Table 4 summarizes the mechanical characteristics obtained from the shear and peeling tests, as

well as the verification of the UEAtc technical guides’ compliance and the overlapping joints’

performance. Since in all cases the requirements for peeling were not fulfilled, the overall

0

10

20

30

40

50

60

70

80

90

100

Oxi Bit APP SBS PVC

Pe

elin

g m

axim

um

fo

rce

(N

)Fibrous acrylic

Liquid rubber


Polyurethane

Liquid silicone

0

10

20

30

40

50

60

70

80

90

Oxi Bit APP SBS PVC

Pe

elin

g m

ed

ium

fo

rce

(N

)

Fibrous acrylic

Liquid rubber


Polyurethane

Liquid silicone

11

performance of all repair systems tested was not satisfactory. It is worth mentioning that this

performance evaluation was made considering the standards applicable to prefabricated

membranes, as there is still no specific regulation for liquid applied products.

Table 4 – Mechanical characteristics from the shear and peeling tests for the overlapping joints

between the prefabricated membranes and the liquid applied products.

Repair system

Shear Peeling

Maximum force (N)

Elongation in the

maximum force (mm)


Maximum force (N)

Medium force (N)


Oxidized bitumen

Fibrous acrylic

134.94 ± 48.8 7.33 ± 1.7 Yes 25.00 ± 5.0 8.35 ± 0.9 No

Liquid rubber 12.56 ± 1.2 8.24 ± 3.6 --- 13.97 ± 1.5 2.71 ± 1.5 No


749.69 ± 38.0 8.78 ± 0.6 Yes 6.60 ± 0.5 4.51 ± 0.6 No

Polyurethane 586.28 ± 137.1 10.89 ± 1.0 Yes 8.72 ± 1.3 4.63 ± 0.3 No

Liquid silicone

17.16 ± 1.5 8.90 ± 4.3 --- 3.06 ± 0.7 1.24 ± 0.2 No

APP polymer bitumen

Fibrous acrylic

121.35 ± 20.8 9.06 ± 1.0 Yes 15.00 ± 5.9 5.30 ± 0.2 No

Liquid rubber 16.06 ± 0.7 5.73 ± 0.9 --- 13.31 ± 0.3 5.48 ± 1.1 No


586.41 ± 15.7 30.72 ± 7.8 Yes 6.22 ± 0.6 4.78 ± 0.3 No


Liquid silicone

35.81 ± 1.9 46.59 ± 18.3 --- 4.53 ± 0.2 2.91 ± 0.1 No

SBS polymer bitumen

Fibrous acrylic

152.97 ± 27.9 7.13 ± 1.1 Yes 20.28 ± 0.9 15.11 ± 2.6 No

Liquid rubber 16.81 ± 1.3 5.58 ± 0.2 --- 13.00 ± 1.0 3.59 ± 1.1 No


438.50 ± 21.6 19.03 ± 12.4 No 6.47 ± 0.5 4.77 ± 0.3 No


Liquid silicone

36.44 ± 8.3 45.29 ± 12.4 --- 6.06 ± 0.7 3.58 ± 0.1 No

PVC

Fibrous acrylic

210.19 ± 37.1 10.39 ± 0.8 Yes 80.94 ± 2.8 62.11 ± 14.6 No

Liquid rubber 11.66 ± 1.6 10.32 ± 3.5 --- 9.56 ± 0.6 1.68 ± 1.4 No


586.44 ± 19.4 13.67 ± 0.4 No 6.47 ± 0.2 5.28 ± 0.2 No


Liquid silicone

43.47 ± 4.8 127.21 ± 19.1 Yes 28.63 ± 1.4 12.48 ± 5.6 No

4. Conclusions

This paper presented an experimental investigation about the performance of different liquid

applied products to repair various prefabricated waterproofing membranes. Performance was

evaluated by means of shear and peeling tests and the UEAtc requirements applicable to

prefabricated membranes were considered as a reference.

For all cases tested, in light of the requirements set by UEAtc (for prefabricated membranes), the

overlapping joints’ performance proved to be unsatisfactory. Although requirements for shear

tests were fulfilled in most cases (where the best performance was provided by the bi-component

cementitious and polyurethane products), the requirements for peeling tests were never fulfilled.

Therefore, according to the presented conditions and considered parameters, the results obtained

show that with the exception of the liquid rubber product, whose testing results were not

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conclusive, none of the liquid applied products studied (fibrous acrylic, bi-component

cementitious, polyurethane and liquid silicone) would be suitable for a rehabilitation or repairing

intervention on flat roof’s waterproofing coatings constituted by oxidized bitumen, APP polymer

bitumen, SBS polymer bitumen or PVC prefabricated membranes.

5. Acknowledgements

The author wishes to acknowledge the Supervisors for their advice, LNEC and IST for funding

the research and providing the resources, the companies Imperalum, Texsa, Danosa, Renolit,

Matesica, Henkel and Sika for supplying the materials and providing application support.

6. References

[1] Instituto Nacional de Estatistica (INE), Surveys 2001: Final results: XIV population general survey: IV general housing survey (in Portuguese), INE, Lisbon, 2001. [2] Lopes, J. G., Revestimentos de impermeabilização de coberturas em terraço. Informação técnica de edifícios, ITE 34, LNEC, Lisboa, 2010. [3] European Committee for Standardization (CEN), NP EN 13416 – Flexible sheets for waterproofing. Bitumen, plastic and rubber sheets for roof waterproofing. Rules for sampling (in Portuguese), IPQ, Caparica, 2001. [4] European Committee for Standardization (CEN), NP EN 12311-1 – Flexible sheets for waterproofing. Determination of tensile properties. Part 1: Bitumen sheets for roof waterproofing (in Portuguese), IPQ, Caparica, 2001. [5] European Committee for Standardization (CEN), EN 12311-2 – Flexible sheets for waterproofing. Determination of tensile properties. Part 2: Plastic and rubber sheets for roof waterproofing, CEN, Brussels, 2000. [6] Instituto Português da Qualidade (IPQ), NP EN 12317-1 – Flexible sheets for waterproofing. Determination of shear resistance of joints. Part 1: Bitumen sheets for roof waterproofing (in Portuguese), IPQ, Caparica, 2001. [7] European Committee for Standardization (CEN), EN 12317-2 – Flexible sheets for waterproofing. Determination of shear resistance of joints. Part 2: Plastic and rubber sheets for roof waterproofing, CEN, Brussels, 2000. [8] Instituto Português da Qualidade (IPQ), NP EN 12316-1 – Flexible sheets for waterproofing. Determination of peel resistance of joints. Part 1: Bitumen sheets for roof waterproofing (in Portuguese), IPQ, Caparica, 2004. [9] European Committee for Standardization (CEN), EN 12316-2 – Flexible sheets for waterproofing. Determination of peel resistance of joints. Part 2: Plastic and rubber sheets for roof waterproofing, CEN, Brussels, 2000. [10] António, D., Rehabilitation of waterproofing coatings in flat roofs. An experimental study on the connection between new and aged membranes, Dissertation to obtain the Master degree in Civil Engineering, IST, Lisbon, 2011. [11] Feiteira, J., Liquid applied products based waterproofing systems in flat roofs. An experimental study on the systems mechanical behaviour, Dissertation to obtain the Master degree in Civil Engineering, IST, Lisboa, 2009.

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[12] Union Européenne pour l´Agrément technique dans la construction (UEAtc), M.O.A.T. nº 64:2001 – Technical Guide for the assessment of roof waterproofing systems made of reinforced APP or SBS polymers modified bitumen sheets, UEAtc, Garston, 2001. [13] Union Européenne pour l´Agrément technique dans la construction (UEAtc), M.O.A.T. nº 65:2001 – Technical Guide for the assessment of non-reinforced, reinforced and/or backed roof waterproofing systems made of PVC, UEAtc, Garston, 2001.

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