Tyvek generally comes in 4' and 5' wide sheets. To make a suitable tarp, footprint, groundcloth, etc. I will need to sew together a couple of sheets. How do I seam seal the Tyvek to prevent leaking at the joint? (Assuming I have determined what kind of Tyvek to buy)
Builders typically get Tyvek in 9' rolls instead of 4' and 5' sheets. You may be able to buy a small piece off of the roll from your local building supply store or find some waste at a local construction site so that you don't have any seams to join.
If you do need to join two sheets of Tyvek, Tyvek Tape is specifically designed for sealing the joints when applied to a house. It's waterproof and adheres well. It's also quite strong, but similar to packing tape, once punctured it can tear easily.