Savings: $40 Groundsheet
Stake out your tent and slide a piece of Tyvek underneath it. Use your marker to trace your tent’s perimeter and cut the Tyvek one to two inches inside the marking (a sheet that’s slightly smaller than your tent won’t collect drips). Visit backpacker.com/groundsheet for a how-to slideshow demo. If your tent’s wider than 60 inches, you may have to tape two sheets together.
Position the Tyvek smooth side down. The slicker surface provides better water resistance and collects less dirt. For some projects (like the bivy and skirt) consider cutting/assembling with the material white-side-out so you’re not a walking Tyvek ad.
Savings: $30 Emergency bivy sack
Lay your sleeping bag out atop a length of Tyvek, and fold the material around your bag’s non-zippered side. Trim the Tyvek to roughly match your bag’s shape, leaving extra material under the hood and along the edges (you want the bivy to be plenty roomy, and you’ll lose two inches when you tape the seam). Tape your bivy’s foot end closed and seal half of the open side. Upgrade: Use Velcro to seal the rest.
New, crisp Tyvek crinkles noisily. After cutting the material and before taping it together, soften/quiet it by washing it in a top-loading machine with cold water (no soap!). Put it through two rinse/agitate cycles and hang it to dry completely before sealing your bivy.
Savings: $95 Rain protection
Make a rain-blocking skirt: Cut a Tyvek rectangle that’s 20 percent wider than your hip measurement and 24 to 36 inches long, depending on your height.(You want it to overlap in front and fall to at least your knees). Adhere two 2-inch-wide lengths to the top corners (see below) to use as waist ties. Rather wear pants? Purchase a ready-made Tyvek pair ($3.50; usplastic.com); go up a size for easier layering.