Tarps that are wider than the raw material used to make the tarp will require at least one seam. Most of our material comes in 61" rolls and our custom tarps generally have a 2" hem on each edge. Therefore, for most material, the widest tarp we can make without a seam is 57".
Seams are generally heat welded with a 1" overlap so (for solid tarps) seams are completely waterproof and they are as strong as the rest of the tarp.
Here are the widths of the raw materials we use:
Seams are generally arranged in such a way as to minimize the amount of material used to make the tarp. If you have a preference as to which way a seam should run let us know and we will try to accommodate this.
If we can avoid having an extra seam by not folding over the hem we will sometimes just use seat belt material as the hem without wrapping it in two layers of material as is customary.