Due to the production methods used, all porcelain & ceramic tiles (including decorative & glazed) can exhibit size variation between batches, as well as variance in both straightness and flatness. Therefore all sizes are nominal. This variance is minimal but it can become more noticeable on larger format tiles. As porcelain tiles are fired they can have a slight bow or warp. To avoid emphasising any warpage, if staggering joints this should be by a maximum of 30% of the overall tile length. Larger tiles should not be laid 'brick-bond'.