I use a polycryo ground sheet from Gossamer Gear. They’re light, durable, waterproof and more importantly, at least to me, it keeps the bottom of the bivy clean.
Use this ultralight ground cloth to substitute or protect your tent floor. This foot print is also used with our tarp shelters. This product is designed with the hiker in mind to keep the weight off your back and dirt off your sleeping bag. It is constructed from industrial grade cross-linked...
No, I never have. I sometimes just use a DCF bathtub floor, clipped up into the shelter, but I've never used a ground cloth in combination with my bivy. I guess it just seems redundant to me, and a bit of overkill in the places I typically spike camp.
Not always. Sometimes I run a bivy on the ground or I run a foam sleeping pad Under it on the outside. I do like having some turf I can spread my stuff out on. Less of an issue in some places like the desert or grass. For when I want One, I have picked up a few ground clothes that I haul based on the trip.
Poly CRO - dirt cheap, light, tears and has a bit of a crinkle sound. Hard to keep in place. 5x7. 2-3oz
Tyvek - still cheap. Crinkles. Not all that light. 4x8 8-10oz
40d seek outside ground cloth - basic. Durable as hell. Reasonable price. 11oz
Dyneema - light as hell. 3x the cost for half the weight. 4oz
Matt mcmattface - stupid name but great product. It is a 1/8 solid foam. 40x80. 8oz. Can double as a sleeping pad supplement / protector or a sitting and glassing pad.
The Matty thing is growing on me. I tend to use the dyneema or the ground cloth when I don’t take matty. They double as glassing tarps.
I just (this week) recieved (have not used) the Polycro to test out. If you want to give it a try, go on Amazon and type in "Duck 286218 Extra Large Patio Door Shrink Film Window insulation kit, 1, Crystal Clear". It is a big sheet you can cut to size and it only cost $4!