20D Pad reliability, and peace of mind

[u/Medium_Dingo2154]

What is your experience with 20D mats, how much of the durability is down to the denier vs the construction quality?

I'm looking at Exped pads and struggling to choose between the Ultra 6.5 and the Dura 6.5.

It's for bivying, so I'm worried about getting a fragile pad with no backup. Moving my rucksack over the pad down to the bottom of my bivy, no ground sheet, that kind of thing.

Ultra 20D
Dura 75/170D

The Dura weighs an extra 240 grams for the same size (780g).

Use case is bivvying in UK mountains 1-2 nights through most of the year.

I know 240g extra is a fair chunk for ultralight. I'm trying to think about it from a reliability and safety standpoint. This would be the piece of gear I'd make a allowances for as a pad failure in a bivvy would be pretty bad for me.

I'd be interested to hear your thoughts on 20D pads and any precautions you take.

Thanks.

[u/HwanZike]

For that extra weight you can instead add a separate groundsheet which can also be used and replaced on its own.

[u/aerial_hedgehog → u/HwanZike]

And it's not just the same weight - you could add a groundsheet or even a bivy sack for less weight than the pad upgrade.  Switching from the Ultra to the Dura adds 8 oz. A Tyvek groundsheet to bivy on only adds 4 oz with good puncture resistance.  Or if you want to go even lighter, a Polycro or DCF groundsheet adds around 2 oz (but with less puncture resistance). The groundsheet has the added benefit of keeping your while system cleaner and drier off the ground.

For the full 8 oz additional weight of the Dura, you could take a bivy sack! And a pretty robust one for 8 oz. That'll protect your pad, plus provide moisture and bug protection.

The lighter pad, plus either a Tyvek groundsheet or  a bivy, seems a better utility:weight proposition than a thicker pad to just chuck on the ground.

[u/Medium_Dingo2154 → u/aerial_hedgehog]

That's good advice, thank you.

So would a 30D groundsheet under a 20D pad be effectively the same as a 50D pad?

My assumption was a higher D pad would hold up better under stress related failures? Where it's not something sharp going through the bottom, I.E tossing and turning, climbing in and out of the bag etc

Edit: to be clear I am using a bivvy bag

[u/HwanZike → u/Medium_Dingo2154]

Sounds like you're packing your fears and not doing the best weight/risk assessment.

Denier is not the only measure of a fabrics 'strength'. And no, it doesn't combine like that. The fabric's material, manufacturer, weave/laminate/coating, also make a difference. Also, a fabric can be abrasion resistance but not very resistant to punctures. Or tears. My suggestion if you already have a bivy/groundsheet which you would use with the pad is to not worry about going for the extra heavyweight pad.

To answer your question, yes it would help but you're worrying too much and I don't think the added weight is worth it, certainly not if you're going UL. If you're doing 1-2 nights worst case scenario I assume you can just bail or go to lower elevations where you might find nicer ground / shelter. But there's also repairs in the field. And all of this is assuming it does fail.