All fabrics will stretch under load although some exhibit different characteristics as a function of time. A structural fabric would not creep under load once it has reached full pretension.
Each roll of fabric is tested in a biaxial rig to measure the stretch in both thread directions at load ratios derived from the form generation computer model.
These figures would then be used as compensation percentages to be factored into the patterning software. The canopy is manufactured undersize so that when installed to its final dimensions it tensions out correctly.
Cottons are most economical and are available in a wide range of colours. Due to their susceptibility to staining and shrinkage they are ideally suited for short term use or where a softer and more natural texture is required.