Winter groundsheet

I’m guessing Tyvek would wet out as well. How about polycyro?

Polycro is too slippy on snow and I like to peg it out if possible. I am using it every night so would like something durable.

I did the backyard ground cloth test several years ago—

Put water hose in a low spot on the grass and fill up with water.  Place prospective ground sheet atop shallow pool and sit on it for 5 minutes—if any water sponges thru it won’t work.

The only thing I found to keep water from sponging thru is a poly tarp aka your typical walmart blue tarp.  Most of these kind of tarps are 5mil and very thin so I bought a 10mil white poly tarp and cut it to size and it’s my standard ground cloth.

I haven’t tried the more durable Vinyl tarps—probably heavier—but probably even more waterproof.

Yes, silnylon will soak through when in contact with anything wet. This was the reason I quit using the sil bags in my pack. Plastic sheets do not, but they are a real pain in the butt to get dried out. As Tipi mentioned, the poly tarps from Walmart work about the best, out of the box. But, they can be a bit heavy and are volume intensive in your pack. Once you cut them down, they tend to unravel easily at the edges unless you use a rolled type hem (double stitched,) too. Fortunatly, duct tape can be used to prevent further fraying, but the whole deal will weigh around 8-10oz.

The best compromise solution I’ve found is simply to coat your existing floor material with mineral spirits and silicone…old style mineral spirits (or white gas in colder weather) and clear silicone caulk mixed in about a 10:1 to 15:1 ratio. Brushed on to both sides, it will pretty much seal the nylon against leaking when in contact with water/snow. It’ll take about 24 hours to set…in cold weather as long as 72 hours. After you are done, it can still breath a slight amount of water vapour, but this is different, and not real leakage, more of condensation related stuff. Anyway, it will add about an ounce to a heavily coated ground cloth and not impede packing size/volume except for slightly. It will also provide a bit of texture and stop the slipperiness of normal silnylon. Anyway, 2 yards should be plenty and it shouldn’t weigh more than 4-4.5oz when completed. Not Ultralight, but in winter conditions, it works well.

Doesn’t sound like you’re headed this way but just to be sure… if slipperyness is an issue, do NOT do Tyvek. I used to do a lot of house framing so used Tyvek for its original intended purpose as a house wrap… it is slick as snot when icy/snowy! Took many a digger when framing in winter :)

Last year I read about Seek Outside’s EVA foam here https://seekoutside.com/mountain-mat/

I thought it may make a good winter groundsheet with the additional benefit of boosting my sleep system if I have an unrepairable failure on my air mat. So I ordered some 1/8″ foam from Foam By Mail: https://www.foambymail.com/VA2/volara-foam-type-2a.html

I have cut a piece to 91″x43″x1/8″ and it came to 9.5 oz. It’s easy to fold being so thin, it almost feels like fabric. As I put it to use I hope to trim some more with experience. Should be waterproof and not slippery. I haven’t yet used it outdoors, hope to next month.

The Neoprene skin looks promising as well.

at 1/6″x48″x80″, it’s about the right size to be used as tent ground sheet.

edit: 1/16″

. Forty Below Tent Floor Foam .

I use 1/8″ eva foam I got from SULUK46 – but they do not sell it any more. Very light (30×76 is 2.65 oz), does not slip around too much on the snow. I have not had issues with melt water coming through; but my pad is  very warm (Thermarest Xtherm), so I don’t get much melt underneath. But where you can find it now I do not know. Other sources of 1/8″ EVA that I have seen seem to be much higher density foam, and thus heavier. I used to always use polyethylene, mostly 2 mil and that worked fine except for the slipperiness.

Tyvek will wet through as a groundsheet, at least after some use – and is heavier than 2 mil poly and even more slippery.

Neporene is usually pretty heavy; even at 1/16″ . Their datasheet says 9 lbs/cubic foot. if that is accurate, then the math would say that a 30×80 piece would weigh 12.5 oz.since 30×80 is a.85 sq yds, that is 6.75 oz/sq yd. pretty heavy when you could get a polyurethane coated nylon, with 4000mm hydrostatic head coating so it is totally waterproof, at around 2 oz/yd. and the polyurethane coating might slip around a bit less than polyethylene sheeting.

I’ve used tyvek in my floorless pyramid shelter directly on the snow with good results. I’ve never had it wet out before. I just read Justin Lichter’s book on winter travel, and that’s what he uses as well.

Exped have a large thin Evazote mat.

http://www.exped.com/usa/en/product-category/mats/doublemat-evazote

Has anyone tried the cuben ground sheets from MLD? Looks like I will give Tyvek a go, then foam if it does not work. As I am on a bike, packed size is not critical but I am going to move to skis in the new year, so would like to perfect my system by then. My mat is a Zlite + XTherm.