The use of fabric membranes is increasing all the
time. They provide a high level of translucency, typically from 10% to 30% and even greater where required to special order.
They provide many benefits to whole of life costs in many installations where savings can be made on electricity etc. The materials are generally maintenance free (apart from normal cleaning) for periods of many years. The design life of a structure depends mainly upon the environment. If pollution from road or industrial sources is nearby, it can affect
the life of the roof. The pretension of the membrane also affects the life span of the installation through greater stability. Materials with improved coating standards also extend the life of the structure. Many varieties of coating are available such as acrylic and PVDF (fluorine as used on non stick appliances). The colour of the membrane also affects the life span of the structure. It can be goog practice to use materials with an increased factor of safety (strength
over potential maximum load) to prolong life. Typical design lives are;
Portable structures, typically 10 years with a 5 year guarantee. Much depends on the way the structure is operated and the wear and tear involved.
Permanent structures using PVC/PVDF, typically 10 years with more in the right conditions. If the building is to be used long term, a higher specification of coating is required. Some of these coatings need to be removed where the
membrane is welded together, which increases cost, so a careful decision needs to be made when specifying roof materials. For extreme long life situations, where the roof needs to be installed for 20 years and more, Teflon® coated glass fibre is often specified for maximum life. | 
