After years of being unhappy with silnylon floors in tents, I now have an MLD Trailstar tarp and am looking for a ground cloth option that I will be happy with. I tried Polycryo... too slippery. Cuben Fiber.... not puncture resistant enough for me. So, now I am at Tyvek or silnylon. In order to alleviate the negatives of the sil-nylon (mainly water absorbing tendencies when used as a ground sheet), I am considering coating each side of a silnylon sheet with a 1:3 silicone/mineral spirits mixture. So I am wondering which will perform better and be lighter/less bulky. Other ideas are appreciated too!

Thanks!

I've always just used a thin plastic sheet cut to be slightly smaller than the tent floor, and duct taped at the corners.

I tried silnylon floor - not waterproof enough

So I coated it with mineral spirits:silicone - then it was waterproof, but the side against the ground started peeling off after a few trips, and the upper side also peeled eventually

Then I got the "Shield" silnylon from thru-hiker.com that Richard tested. That has worked great after a few trips. My therm-a-rest matt kind of slipped around on it so I put some splotches of mineral spirits:silcone and now it's better.

Dale, I've used the polycryo for quite a few years now, like any other material, I have to camp on fairly flat ground, or with my tossing and turning at night, I worm my way to the downhill side. Tyvek is about 2.5X as heavy as the medium weight polycryo.
Duane

My new idea was an insulation paper used here in Australia to wrap a house with for insulation rating requirements. One side is that reflective material and was going to place it only under my sleeping mat to reflect the body heat back up (had heat loss issues on a couple trips and I lost a fair bit of sleep making the trip uncomfortable). Not sure on waterproofness. The size for the mat only is 170g.

I have a groundcloth that I use that I made for myself of silnylon with both sides treated with appropriately diluted GE II silicone & mineral spirits. While the slight stickiness of the silicone has caused the underside to pick up a fair amount of grunge during use, it is holding up very well so far. I have not seen any signs of peeling of the silicone like Jerry has experienced. I am happy with it (although it may be a little on the heavy side), but I bought a piece of Tyvek to cut and try on another shelter in the future just for comparison purposes. I have wadded/wrinkled and washed it already to soften it, but I need to wait for a solo trip to try it out...

There are different weights of Tyvek not sure any of them are waterproof, something to think about. Designed to let moisture through in one direction.
Duane

I've found polycro too fragile and nylon too heavy so I use a 1.5 or 2 mil thickness painter's cloth (Lowe's or Home Depot).

Duct tape loops at each corner with short ties of Triptease cord and small plastic snap hooks attatch it to my tent (TT Moment) so winds don't blow it out from under the tent.

If you go decide to use silnylon then I'd go with a 5:1 ratio of odorless mineral spirits to clear GE silicon caulk. (A 3:1 ratio is too thick, best for seams, not large areas of cloth.)

For coating or recoating silnylon, there are as many "formulas" out there as people it seems. These are some that I have used (over ten years of recoating tarps, tents and ground cloths.)
1) For recoatoing silnylon: 20:1 or if it is badly streatched 30:1 both sides.
2) For recoating silnylon floors: 15 or 20 to 1, both sides
3) For coating a small piece of untreated ground cloth: 15:1, both sides.
4) For sealing seams, a 5:1 mix applied with a small brush or syringe works pretty well.

After drying a light dusting of talc (unscented baby powder, NOT corn starch) will remove stickiness. It takes about 24-48 hours to completely dry. The mineral spirits evaporate and the curing of the calk both happen at different rates.

The peeling happens when the coating becomes stronger than the fabric/sealer bond. That is, the calk sticks to itself stronger than it sticks to the fabric. Generally, washing silnylon is not recomended but if you plan on recoating it, it helps with adhesion. Two coats will also bond through any breaks in the origonal coating to increase the actual bond on the fabric if it is applied within about an hour or so.

On silnylon, thicker is NOT better. Thicker coating will peel far faster than thin coatings. Two very thin coatings (40:1 or 50:1) will often revamp an older tarp that is wettin through, but not leaking. Light coatings often repel UV much better. White silicone calk has tungston oxide in it which stops UV. So coating a .2oz coating over a white tarp will extend the life expectancy by about double. UV damage will often manifest itself as weaker portions of fabric: pulled loops or growmets, small splits. Note that while not technically an adhesive, it will bond fibers togetehr making a fly or tarp somewhat stronger, sort-of repairing a UV damaged tarp for a year or two.

I'll bet that the silcone:mineral spirits that I put on my floor that peeled was less diluted - like 4:1 or something but I don't remember for sure.

That makes sense to dilute it more.

On the other hand, if the Sheild silnylon is waterproof, that would be better if you're talking about making a new floor.