Measuring roofing system flexibility

What is elongation at break and how to measure flexibility with a liquid applied roofing system.

What is Elongation at Break (EaB)?

Elongation at break is a mechanical property that measures the ability of a material to stretch or elongate before it breaks or fails. In the context of a liquid-applied roofing system, elongation at break refers to the maximum amount the roofing material can stretch before it ruptures or tears apart.

Liquid roofing systems are applied generally with a fibreglass reinforcement and then cure or harden to create a durable membrane. Elongation at break is an important property to consider in these systems because roofs are subjected to various stresses, such as thermal expansion and contraction, foot traffic, and weathering.

When a roofing system has a high elongation at break, it means that the material can stretch over a greater distance before it reaches its breaking point. This property is especially important in areas where the roof may experience significant movement or stress, such as expansion joints or areas prone to temperature fluctuations.

High elongation at break allows for the roofing system to accommodate the movement and stress without cracking or tearing. It helps to maintain the integrity of the waterproofing layer and prevents water infiltration, which can lead to leaks and damage to the underlying structure.

We provide elongation at break values as a percentage. For example, a liquid-applied roofing system like Fibrecoat, for example, has an elongation at a break point of 300%, indicating that the material can stretch up to three times its original length before breaking.

Thermal expansion and contraction

Thermal expansion and contraction refer to the physical response of a material to changes in temperature. When a roof is exposed to temperature fluctuations, its materials expand or contract accordingly.

When the temperature increases, the roof materials expand due to the increased molecular activity within the material. Conversely, when the temperature decreases, the roof materials contract as the molecular activity decreases. This expansion and contraction phenomenon can occur in various roofing components, including the roof membrane, metal panels, and structural elements.

Thermal expansion and contraction can have significant effects on roofs. If the roofing materials are unable to accommodate these dimensional changes, it can lead to various issues, such as:

  1. Stress on the roofing system: When a roof expands or contracts, it places stress on the materials and connections. If the roof does not have adequate flexibility to handle these changes, it can result in material deformation, joint separation, or structural damage.
  2. Leakage: Inadequate allowance for thermal movement can cause seams, joints, or connections to open up, creating gaps that allow water infiltration. This can lead to leaks and water damage within the building.
  3. Damage to roofing components: Components such as flashings, fasteners, and sealants may experience excessive strain during expansion or contraction. This can cause them to weaken, crack, or detach from the roof, compromising the overall integrity of the roofing system.

To address the effects of thermal expansion and contraction, roofing systems are designed to incorporate specific features, such as:

  1. Expansion joints: These are intentional gaps or flexible connections in the roof system that allow for thermal movement. Expansion joints accommodate the dimensional changes without placing excessive stress on the roofing materials.
  2. Flexible roofing materials: The selection of roofing materials with good elongation properties, as we discussed earlier, can help the roof system withstand thermal expansion and contraction without cracking or tearing.
  3. Proper installation techniques: Ensuring that the roofing materials are installed with the appropriate allowances for thermal movements, such as leaving gaps at expansion joints or using flexible adhesives, can minimize the potential for damage due to expansion and contraction.

By considering and accounting for thermal expansion and contraction during the design and installation of a roof, it is possible to mitigate the associated risks and maintain the long-term performance and durability of the roofing system.