(57) A woven fabric material is formed from tapes of synthetic resinous material such as polypropylene, either the warp tapes or the weft tapes having discontinuous longitudinally extending localised weakened areas formed in them, for example discontinuous longitudinally extending grooves in the tapes. The woven fabric is then stretched by stretching longitudinally and at a raised temperature that set of warp tapes or weft tapes which does not have the weakened areas, thereby causing the tapes with the weakened areas to split at those areas and open up to take on the appearance of a network. The stretched woven fabric material is cooled in the stretched condition so that the final stretched woven fabric material obtained has a substantially greater area and a lesser overall thickness than the base woven fabric, i.e. the fabric before it was streched.