DIY plastic footprint: vestibule?

I always put my ground sheet inside the tent because we get gully washers here and heavy deluges causing ground water to form pools under the tent. If you use a ground cloth under the tent floor you will end up with small water pools forming on top of the sheet and below the floor, unable to drain.

A decent tent floor with decent denier numbers should be able to handle small rocks and thorns. Plus, an inside ground cloth will still protect your inflatable sleeping pad from any errant thorns.


Here's an example of my inside ground cloth. I like white because you can see stuff on the floor.

Other than making the footprint slightly smaller than the tent floor, I've never worried about making my own and I live in the great soaking wet PNW. I like Tyvek slightly better than painters tarp because I've found it to be quieter after a bit of use. I've always put mine UNDER the tent vs. inside as the main purpose of it for me is to protect the tent floor.

The main purpose of a ground sheet for me is to protect my inflatable sleeping pads from puncture holes. The reason I do not use an outside ground cloth below the tent floor is for rainstorms like in the above video. All this water will settle between the ground sheet and the floor no matter if a piece of the sheet is sticking out beyond the tent floor or not.

I use 4 mil plastic cut about 4 inches smaller on all side than my tent and it goes under the tent, nothing for the vestibule.

First off, in my case Hilleberg has the best tent floors on the market (in my opinion) and I've never had a water leak from the bottom up even without an outside ground sheet.  Even in conditions as shown in my video.  But in such conditions I do not want my waterproof ground cloth below the tent to collect water.  Simple.

The point of an inner ground cloth is many-fold:  To allow pools of ground water to drain away and not get sandwiched between two waterproof layers as mentioned, i.e. the ground cloth and the tent floor---it makes for drier conditions overall.  Water can't drain fully if sandwiched between a ground sheet below the tent floor.

Second, the ground tarp provides protection for my inflatable Thermarest, whether inside or out.

Third, the inner ground cloth keeps condensation and/or condensating ice from below my sleeping pad and places it between the tent floor and the inside ground tarp.

Finally, there's the problem with most ground cloths whether under a tent or inside a tent:  Namely, they leak.  Do this test in the backyard:

**  Get water hose and fill up a low place in the grass with a small pool.
**  Over top throw your tent floor on the water and sit down on your butt for 5 minutes.  No water should seep thru.
**  Now do the same test with your ground cloth; tyvek, ripstop nylon, silnylon, cuben.  Sit on it for 5 minutes.

This test mirrors real world conditions on wet slushy snow or in deluges as in my video.  Body weight should not allow water to sponge thru your tent floor or your ground cloth.

One of the few tarps I have found to not allow seepage are the walmart style blue tarps.  They can be cut to size and come in many different thicknesses---mils. 

The next test for ground sheet thickness is to go find a rose thorn and try and poke it thru your ground cloth.  It should be thick enough to turn away the thorn.  About 10 mil works good---
www.sears.com/dry-top-312164-12-by-16-foot-super/p-SPM11918100919

High Sierra Fan---I need to get some of that and try it out with my water-butt test and my thorn test. It looks interesting.

 I must admit having the ground cloth extend into the vestibule to prevent moisture from the ground creating condensation is something that never gave much thought to. I always kept the vestibule ground open in the event of wet gear storage, will need to give myself the option for either situation.