Waterproofing Membrane Bituminous Membrane Waterproofing Roofing

Whether you're an architect, roofing applicator or anyone involved in selecting the right bituminous roofing, it's hard to know where to begin.

Close up view of bitumen membrane applied on roof at parapet

Looking at the different properties and characteristics of each bitumen roof product, sometimes it’s challenging to define which one is the most recommended for your local market or each specific project.

Therefore, we prepared a sequence of questions and answers to guide you through the selection of the correct bituminous product according to your project needs.

Let's Go Through Your Project Step by Step

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1. Where will the product be applied?
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2. What is the intended use?
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3. What are the requirements?
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4. What is the life expectancy?
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5. Are there any other limitations?

1. Where Will the Product be Applied?

The temperature exposure and local weather helps guide the selection of bituminous compound type that should be used: elastomeric (SBS), plastomeric (APP), elastoplastomeric (mix of SBS and APP) or even oxidized bitumen (which is not polymer-modified).

Always keep in mind:

Characteristic SBS APP Oxidized
Heat resistance
< 100 °C up to 140 °C < 80 °C
Flexibility at low temperature
≤ -30 °C ≤ -15 °C > 0 °C
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2. What is the Intended Use?

The top surface of the membrane is chosen according to where and how it will be applied.


  • Smooth surfaces (talc, sand, PE foil): are indicated for ballast systems or as a base sheet in a multi-layer system to ensure perfect bonding of the overlying layers.
  • Covered membranes, such as granulated surfaces: protects the compound and can be used as an exposed layer.
Icon of roof on building

3. What are the Requirements?

The minimum expected performance requirements must be provided in order to select the reinforcement - the part responsible for mechanical properties.

Here are some examples:

  • Polyester: increases strength and elongation
  • Glass fiber: increases dimensional stability
  • Aluminum: works as a vapor barrier (most indicated to vapor control layers)


The type of reinforcement also defines your system build up, i.e. if the membrane is applied as a single or double layer.
Usually, glass fiber reinforced membranes are always recommended for double layer systems.
And single layer membranes are suggested only for polyester reinforcement heavier than about 140 gr/m2.

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4. What is the Life Expectancy?

Flexibility of the bitumen membrane at low temperature is a general indicator of quality.

The lower the flexibility is in cold temperatures, the higher the durability of the membrane due to the amount and quality of polymers.

Additional aging tests are recommended to check the thermo-oxidizing profile.

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5. Are there any Other Limitations?

What other unique project requirements or limitations do you have to face?

Fire performance?
Local approvals?
Anti-root material required?
Safe to apply?

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Other Properties of Bitumen to Consider

After specifying the project needs, it’s time to check other bituminous membrane properties to build-up the appropriate and required system. These are key characteristics that SikaShield® bitumen can offer.


Cold Flexibility

The cold flexibility or flexibility at low temperature is a general indicator of quality, because it is related to weather conditions and also to the life expectancy of the membrane.

To help identify and select the right product, SikaShield® is named numerically according to the different cold flexibility ranges. The concept is simple - the higher the number, the lower the cold flexibility and better the performance.

Cold Flexibility Numeric Value
-35 to -40 °C 8
-25 to -30 °C 7
-20 to -24 °C 6
-15 to -19 °C 5
-10 to -14°C 4
-5 to -9°C 3
0 to -4°C 2
> 0 °C 1


The reinforcement is responsible for the mechanical properties of the bituminous membrane, such as strength (tensile force), elongation and tear and shear resistance. These values must be in accordance with the features of the building to guarantee the resistance of the membrane against movement and applied loads. The most popular reinforcement materials include: glass fiber, glass fleece, aluminum, non-woven polyester, polyethylene foil and some other combinations.

SikaShield® bituminous membranes are available with all these options. The same concept as used with cold flexibility is adopted - a number is used to identify the different types. The higher this number is, the better the mechanical properties and more flexible the membrane is for different uses and applications.  

SikaShield® bitumen membrane shield with roll of roof waterproof membrane

Top Surface

SikaShield® bituminous membranes are also available with different surfaces, which are classified into two groups - smooth or self-protected.

Smooth surfaces

Ensures the bond of the overlying layer

  • Polyethylene foil
  • Sand
  • Talc
  • HDPE
  • Non-exposed roofs (with exceptions)
  • Below-ground applications
  • Under layer or intermediate layer in multi-layer systems
  • Upper layer in multi-layer systems with protection
  • “S”: refers to sand, which gives the extra advantage of bonding the thermal insulation with adhesives
  • “PE”: refers to polyethylene foil
  • “T”: refers to talc
Self protected

Protects the membrane against UV rays

  • Granules
  • Aluminum
  • Geotextile
  • Exposed roofs
  • Upper layer in multi-layer systems without permanent heavy surface protection
  • “MG”: refers to mineral granules
  • “ALU”: refers to aluminum foil
Juliana Grippa

Juliana Grippa
Corporate Product Engineer Bitumen
Target Market Roofing
Sika Services AG