So I was out over the weekend on top if a big hill and found a nice flat area to camp. Up went the Mini Peak and out came the bivy bag. After just an hour of sitting on the bag I could feel damp coming through the bivy from the ground... then by morning after a pretty steady downpour, a lot of water had soaked through the bivy and now my mat and sleeping bag were well damp.
Am I expecting too much from a bivy to keep me dry if the ground beneath me is saturated? I have an MSR ebivy. ..nice and small and supposedly waterproof.

So i guess I'm asking if it's time to try and reproof the bivy or time to replace it..??

Am I right in saying the weight of a mat and person puts alot of strain on whatever number hydrostatic head your bivi is?
Same way gale force rain can penetrate more than a light sprinkle

Most of the time dry ground is fine, but if I think its going to be quite soggy or soddon I use a very small ground cloth to boost the waterproofing (this ground cloth doubles as a soft mudguard under my rack) and find this is more than enough, if not making a bivi partly redundant

Reading the spec of the product its not a waterproof bivi

Silnylon top and tough, DuraShield™-coated waterproof bottom protect from dew, frost, wind and light precipitation while adding warmth to any sleep system.

Ok in a bit of light drizzle, but not enough protection for wet ground or heavy rain.

Unless it is weather is like the current spell we are having, I always take a ground sheet of some sort. I have an Oooktub type bathtub floor. Weighs 200g, packs down to bugger all and gives me that piece of mind.
All the best.
Adam.

The floor is waterproof, MSR quote a HH of 10,000mm ... which doesn't explain why water seemed to be coming through the floor

Could the damp mat / bag in the morning have been condensation? Sounds like ideal conditions.

EDIT: are the seams between floor and top taped?

Thanks all... i'll check if the seams are sealed when I get home. The conditions on Saturday (when i pitched up) were fine. .. sunny with a breeze so I could sit with doors open having some grub. It didn't take long for the dampness to come through the bottom of the bag and when I prodded the ground it did feel wet. Think I'll maybe look at getting a groundsheet of some sort and try to pick a better pitch next time!

if it looks wet i jut bring my bigger gortex bag as its really vaguely exciting in a down poor! heavy and bulky compared to a light weight bag but at least its all ways been dry even in really awefull weather !

Hammock time ...