Bivy fabric choices

Discovery Fabrics in B.C. sells neoshell

They have both no stretch and stretch versions.  Maybe what you describe is a stretch version?  I don’t know if that makes any difference.  It seems like maybe if it stretches, any pores will get bigger and let through water???

Neoshell has fluorocarbons.  That could be a feature if that makes it work better.  Not if it gives you cancer : )

If you make the neoshell to bottom fabric seam a flat felled seam, with the fold going down so it’s like a roof shingle directing the water down, you don’t need the seal the seams?  That’s what I do and haven’t found it’s necessary to seal the seams.  You could not seal them, use it, if it leaks then go back and seal it.

I have breathable nylon floors because that fabric is lighter.  It doesn’t need to be waterproof because my sleeping pad is.  And I use a polycro ground sheet.  I don’t need a third layer of waterproof.

I have a neoshell jacket that works quite well in the rain.  I got the fabric from Discovery fabrics.  Kind of expensive.  A little different application than a bivy.  I have the no stretch version.

I thought neoshell was FC-free 😕 don’t need more of that stuff produced. Back to the drawing board 😅

I actually considered sewing or glueing the top directly to the pad. Maybe I should just revisit that idea.

I can get a non-stretch neoshell, but only in bright red, at almost double the price and 155gsm/4.6osy.

I see your point on the seams, but I’m surprised you can get away with a non-waterproof floor.

What kind of environments are you using it in? A main reason I want the bivy is for beach camping, so it needs to handle a rainy night on wet sand.

I use it on wet surfaces without problem.  Wet organic matter like moss and bark dust.

The polycro is waterproof.

Once I camped where it became a puddle about 1/2 inch deep.  My mattress was 1 inch thick.  The bivy was not waterproof.  I just kept sleeping and stayed dry.  In the morning it had been absorbed, puddle gone

I definitely try to avoid that, but the mattress did keep me dry.

Didn’t consider the groundsheet. I much prefer the simplicity of a waterproof bottom and no groundsheet though.

I used to think that until I heard from people on this site

When I did bivy with waterproof bottom, then in the morning it’s wet and dirty.

With a polycro groundsheet, it’s easier to put it out to dry, shake the stuff off it.  If I have to pack it wet, just fold it against itself.  A couple ounces.  The bivy is probably a couple ounces lighter because it has lighter weight fabric.

Something to consider, not necessarily best for everyone.

Good point. I’ll think about it.

For waterproofing seams, I find that introducing a couple of layers of double sided basting tape into a proper felled seam makes them much easier to sew, and they end up waterproof without additional sealing.

The adhesive does gum up your needle and you may have to stop at times to clean it. Dipping the needle into liquid detergent helps.

Something you can test out with scraps of your fabric combination for very little cost.

It does make for a slightly bulkier seam, but then again, so does conventional seam sealing.

The adhesive does gum up your needle and you may have to stop at times to clean it. Dipping the needle into liquid detergent helps.
I found that a small drop of sewing machine oil worked wonders for gliding through the adhesive layers.
One can use silicone oil when sewing silnylon, but finding that (in the consumer world) is more difficult.

Cheers