Floor Hydrostatic Head and Leakage

I had recently purchased a Big Agnes Copper Spur 3-person tent. We were camping outside of Horseshoe Meadow in the Sierras when we got hit by a large storm. By chance, we had pitched our tent in a depression. When I woke up in the morning, the floor was lifted off the ground by about 2 inches, it felt like a waterbed. When we packed to leave, everything in the tent was dry. Now, this was a new tent so I suspect that this would not be the case right now.

Here are the AI specs on the material.
The floor of the Big Agnes Copper Spur tent (including UL and HV UL models) is made of proprietary HyperBead™ 20-denier solution-dyed nylon ripstop. It features a 1500mm waterproof polyurethane coating and is completely free of intentionally added PFAS chemicals.

I can vouch for SlingFin’s 1800mm HH floors – at least so far. We hiked several sections of the Cape Wrath trail in Scotland in early May using their Cinder Cone pyramid along with the Mesh inner tent and we had 2 nights where water pooled under the tent floor with no leakage, and no soak through under pads, etc. We shall see how that holds up over time.

Thanks guys.  The Xmid2 was new at the time, the Xmid1 had a fair number of nights on it so may be seeing some wear, but the seepage looked pretty even and less local like you’d see from abrasion.  I wonder if maybe these particular tent floors aren’t as bomb proof as the competition, the price to pay for dropping a some ounces.

I have often noted dampness under my pad in those conditions, but have never been certain where the water was coming from. Through the floor? Or condensation collecting? It’s hard to know.

I would guess that it’s less a question of which fabric is under you than how much use that fabric has had. Brand new, you’re probably fine. Any tent light enough for backpacking has a floor that will get worn spots and/or tiny pinholes after a while. If I wanted a reliably waterproof floor for where I knew I couldn’t find better sites, I think I’d add more coating to the floor I had, either with a commercial recoating product or a home brew solution.

Started to get a slight seepage through the floor of my blue summer tent somewhere on the Tour de Mont Blanc in Europe: light silnylon as used also for the fly. Bought some silicone sealant in a large Italian ski town, booked into a cheap hotel there, spread the tent out on the baalcony and spread a thin (very thin) layer of sealant across the floor. Many years later, the floor is still working.

Cheers

Dan recommended making a blend of 20% silicone and 80% mineral spirits and applying it to the outside.

I applied Seam Grip+WP to pinholes on the  inside of my Xmid2 but it stayed “sticky” pretty much forever so that it couldn’t fold or store properly so I just bought a new inner.  Adding starch or some other fine powder was just a temporary fix.   The Seam Grip+WP was supposed to work so this experience has spooked me from trying a more ambitious silicone based recoat of the other side.

Is this more an issue of site selection?  Would you have been able to dig a very small trench around your tent to collect water?  Have you considered using a Tyvek footprint?  That PU coated floor of your MEC tent will eventually delaminate and let the water pour in.

These are provincial park designated sites on back country routes.  They very heavily used over decades.  Every possible spot to put a tent is heavily compacted and depressed in the middle. Easterners will recognize the description.

Given the shape, water collects between footprint and floor, the footprint helps trap a layer of standing water but it’s still helpful to reduce abrasion from the exposed roots.

Agree the clock is ticking on the mec.  Like many here, I’ve tossed out a few tents over the decades due to pu failing

I have coated the flys and floors of my Tarptent tents,, which are Silnylon, with a mixture of (by volume)  1 part GE clear silicone to 5 parts “odorless” mineral spirits. I put it in a clean plastic jar and shook it hard for a minute before pouring some into a small roller tray. Using a low knapp roller I coated the fabric of the erected tent about 2 ft. x 2 ft. area at a time. Then I wiped it down right away with a blue paper shop towel. Standard white paper kitchen towels leave paper fibers behind.

For floors I put the floor exterior over a small folding table and coated it. A day in the sun is sufficient for drying Silnylon fabric.

This process WORKS and can be reapplied a few years of wear later.

Thanks for confirming how long this lasts, Eric.   I have a tent with badly pinholed floor that I’ll give this a shot to as a test mule.

not to disagree with you eric, just another data point

i’ve used odorless mineral spirits that didn’t dissolve the silicone so it just created a mess.  Maybe some odorless mineral spirits works and other doesn’t.  Try a small test batch first, put on test fabric, let cure and see if that works

I’ve coated silnylon before but it started peeling off after a while.  Maybe I didn’t use enough mineral spirits.  After your test piece has cured try to rub it off vigorously.

Brands of silicone and solvent apparently matter.

Even just silicone calking my bathroom it was obvious that there were some pretty notable differences between silicone brands

Good advice here though I’ve yet to confirm for myself:

https://backpackinglight.com/forums/topic/100947/#post-2181048

Tldr: 100% silicone like GE, and mineral spirits with no kerosene: Kleenstrip or coleman fuel if below 60F.  If it peels off, it’s on too thick

Eric,

Thank you for your detailed explanation of your procedure for resealing your tents.  I found this very helpful.