When you are in tensile structure business long enough, there will be situation when the customer request for membrane inspection and then replacement.
Most membrane manufacturers (Ferrari, Mehler, Sattler) give 10 - 15 years of warranty saying that the membrane will retain 95% of tensile strength over this period.
Taking a closer look at membrane's layers. It's composed of base fabric, PVC coating and top coating layer, all this build up into 2-3 mm thick of membrane.
Base fabric - Usually made from woven polyester yarn in white color, This layer responsible for tensile strength of the membrane. Structural membrane's classified into 4 types of tensile strength ranging from 3000 N/5cm to 5000 N/5cm. Polyester is plastic, so it will be affected by UV light and moisture. When exposed to sunlight for long time, it will be brittle and start to lose its strength.
PVC coating - Its function is to protect base fabric from weather, both moisture and UV light. Liquify PVC is poured over the base fabric and spread over the surface with knife. The PVC can be made into many colors, but only white is widely used for permanent structure due to its less heat absorption. PVC is prone to UV light; the oily compound will slowly float up to the top surface and harden the material. Some UV stabilizer is added to increase UV and yellowing protection.
Top coating - This coating layer is to further protect PVC from degradation. It's usually made from diluted PVDF lacquer.
The longevity of membrane material depends on the following factor.
Sun light exposure time per day. The wall or facade membrane usually last twice longer than roof membrane.
Top coating material. Truck cover membrane usually has no coating at all. It will last at most 2 years under Thailand weather conditions. Acrylic coating lasts a bit longer up to 5 years and finally PVDF coating membrane will last 10-15 years at most.
Moisture. This is not the main factor of membrane degradation and is avoidable. Water can seep into the base fabric (Like a wet cloth) from the cutting edge and damage the yarn. Most manufacturers have added some chemical to make base fabric less absorbent to water.
The underside of the membrane may look brand new (Except yellowing) but the most damage part is at the top PVC layer.
Here's an example of over due to replace membrane. The topcoat layer has long gone, maybe in its 7-8 years and the PVC layer was exposed without any protection. The PVC then get harden by losing its oily compound and chipped away. The membrane is still can, undergo tension load but it will decrease its capacity significantly. Water can seep in, and leakage may occur.
I highly do not recommend anyone to walk on any 10 years and older membrane roof. It can instantly tear apart. Anyway, degraded PVC is recyclable, especially Polyester base fabric. It can be shred and remelt for other purposes.
Membrane has a certain service life but it's replaceable using the original steel frame.
Tensile Creator, we offer membrane replacing service with experience installer. The building still can be in service during installation. Please contact us for more information.