Whether you're an architect, roofing applicator or anyone involved in selecting the right bituminous roofing, it's hard to know where to begin.
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, followed by other properties of bitumen to be considered.
Let's Go Through Your Project Step by Step
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 |
2. What is the Intended Use?
The top surface of the membrane is chosen according to where and how it will be applied.
Usually:
- 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.
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.
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.
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 Sika Index 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.
| 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 |
Reinforcement
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.
Sika Index bituminous membranes are available with all these options.
Top Surface
Sika Index 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
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Self protected
Protects the membrane against UV rays
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Let Us Help You Choose the Best Bitumen Membrane
Author
Juliana Grippa
Corporate Product Engineer Bitumen
Target Market Roofing
Sika Services AG