oh yeah? over a billion of people don't have TP right now, today. Guess what? they dont die of the lack. If the American Indians didn't have it 200 years ago, obvioiusly then, you don't need it for shtf, either, if you are sneaky enough and careful enough. We have newspapers, catalogs, magazines, yellow pages, etc. It aint like you're going to be flushing it, post shtf, you know. So the lack of "bio-degrability" means nothing. All you really need is some leaves, corncobs, etc, and soap and water.
why would you need to build anything? If shtf, so many will die that there will be a huge surplus of housing. Many of the Viet Cong lived in tunnels for 30 years, guys, while they fought the Japanese, the French and us. they WON, remember?
https://www.youtube.com/watch?v=psP5G7aodj8
This cleans you right up and gets you some exercise. We can learn a lot from mans best friend.