[quote=Frankie]I need to cover the "shelter group" in my 72 hours evacuation and shelter-in place kits.

What is the reason behind the 5:6 ratio (8' × 10' and 10' × 12') instead of square most poly tarps at hardware and camping stores come in?

Thanks
Frankie

I believe the odd number is because of the number 5 as in the material is cut in 5' wide strips. At least it is with sil-nylon and presumably other nylon. This tidbit of information came from a small market tent maker. It should have a at least one seam if it is an 8x10 or 10x12 sheet. Also a rectangular size is usually more versatile than a square sheet with more variations on how to set up despite the examples shown it that tarp tutorial.

I've got 3 sheets - a 10x13 (yes that's an oddball size) ripstop poly, a 6'x8' lightweight silnylon tarp (with a 4' seam) and a 10' wide roll of 2 mil painter's plastic. That not counting my 2 tents. I find having some sort of extra tarp is handy when setting up camp in the rain - the extra square footage of rain cover serves to make supper in comfort.

Plus - think outside the box - think of that plastic shower curtain hanging up in that bathroom that is about 6'x7'. Leftover tyvek building wrap also makes a good tarp. Large contractor or orange garbage bags cut along the seam will open up to a nice size. There is no reason to limit yourself to store bought conventional tarps. Cordage wrapped around the edge of tarp with something small and solid like a pebble will serve as a tie out point. Grommets are not necessary - just conventional.