The complete guide
Tent Footprints and Ground Tarps: How to Choose and Use One
The problem with pitching straight onto dirt
Most tents fail from the bottom up. The fly can be ten years old and still shed rain, but the floor gives out first, because the floor is the part being ground into gravel every single trip. You drag the tent into position, you kneel on it while threading poles, a kid runs in with boots on, and all of that happens on a surface full of stones, sticks and grass stubble.
Then there is water. Ground moisture does not need rain to show up. Grass holds dew, sand holds the tide from six hours ago, and clay holds whatever fell last week. A tent floor pressed flat under your body weight will eventually wick that damp through at the pressure points, which is why people wake up with a wet patch under their hips and blame the tent.
A separate sheet underneath solves both problems at once. It takes the abrasion, and it puts a waterproof barrier between the dirt and your floor. It costs a fraction of a tent and it is far easier to replace.
How a footprint actually works
There is nothing clever going on. A footprint is a flat panel of tough, coated fabric laid where the tent will stand. The tent goes on top. The sheet absorbs the rubbing, the puncturing and the moisture.
The fabric matters more than anything else. This one is 420D Oxford, a woven polyester with a waterproof treatment. The "D" refers to denier, a measure of yarn thickness, and 420D sits in the sturdy range for a groundsheet. It is heavier than the ultralight silnylon sheets that hikers use, and far tougher than a builder's plastic sheet. It also survives folding. Thin plastic creases, goes white along the fold lines, and splits after a dozen trips. Woven fabric does not.
The second thing that matters is the eyelets. Metal grommets set around the edge mean the sheet can be pegged flat so it does not slide or flap, and it means the same sheet can be hung overhead as a simple sun or rain cover. That double duty is the reason a lot of people carry one even when their tent already has a floor they trust.
Getting the size right
This is the medium, at 1.8 x 2.2 m. It is a natural match for two person tents and many three person tents.
The rule that trips people up is that your footprint should be the same size as your tent floor or slightly smaller. Never larger. If the sheet pokes out past the edge of the tent, rain running down the fly lands on that exposed lip and runs straight underneath you. You end up with a shallow bath between the two layers, which is worse than having no footprint at all.
So measure your tent floor. If the sheet is a bit bigger on one side, fold the excess back under. It takes five seconds and it is the single most useful habit with any groundsheet.
If you run a large family tent, the medium may only cover the sleeping area. That can still be worth doing, since the sleeping zone is where the pressure and the damp matter most, but go up a size if you want full coverage.
Who this suits
Car campers get the most obvious benefit. You are already carrying a heavy tent, so 367 grams is nothing, and the sheet means you can pitch on a gravel site without wincing.
Hikers and cycle tourers care about weight, and this sits in a reasonable band. It is heavier than a cut-down polycryo sheet but considerably tougher, which is the right trade if you pitch on rocky or scrubby ground. Anyone looking for a good hiking tarp shelter can also use the grommets to rig it as an overhead tarp on a fine night and skip the tent altogether.
Families and day trippers will probably use it as much away from camping as at camp. It is a clean surface for a picnic, a mat for a beach day, a cover for firewood, and a place to lay out gear when you are sorting the car at a trailhead.
Four wheel drivers and festival goers use them as awning fabric and ground mats. The grommets make it easy to lash to a roof rack, a pole or a fence line.
Choosing between types
If you are comparing options, here is how the main groundsheet styles stack up.
Brand-specific footprints cut to match one tent model are the neatest fit and usually the most expensive. They are sized exactly to the floor and often clip into the tent poles.
Generic woven tarps like this one cost less, fit a range of tents, and can be rigged overhead. They are the practical middle ground, and for most people the best camping ground sheet is a generic sheet in roughly the right size rather than a branded one.
Plastic sheeting from a hardware store is the cheapest and the shortest lived. It works for one season, tears at the corners, and has no eyelets.
Ultralight film sheets weigh almost nothing and suit gram counters on soft ground, but they puncture easily and offer no real second use.
Pitching it properly
Clear the ground first. Thirty seconds of kicking away sticks and stones does more for the life of your gear than any fabric spec. Then lay the sheet out, square it to where the tent will go, and peg the corners through the grommets if it is breezy. Pitch the tent on top, then check the edges one last time and fold in any overhang.
If you are using it overhead instead, pick two solid anchor points, thread cord through the corner grommets, and build in a slope so water runs off one side rather than pooling in the middle. A sagging tarp with a puddle in it will stretch the fabric and strain the eyelets.
Looking after it
Keep it clean and keep it dry. Shake out sand and soil before it goes in the pouch. If it is muddy, sponge it with cool water and a little mild soap, rinse, and hang it until it is completely dry. Do not bleach it, do not tumble dry it, and keep it clear of campfire sparks, because synthetic fabric melts rather than chars.
Store it loosely folded in the supplied pouch somewhere dry. If you have to pack it damp on the trail, unfold it the moment you get home. A sheet that is dried properly after every trip will see out more than one tent.
Small holes are worth fixing straight away. Clean the spot, dry it, and patch both sides with waterproof repair tape. Left alone, a pinhole turns into a tear the next time you drag the sheet across gravel.
The short version
A footprint is a cheap piece of fabric that protects an expensive piece of fabric. This one is 1.8 x 2.2 m of 420D Oxford with a waterproof finish, metal grommets around the edge, and a weight of 367 grams including nothing you do not need. It goes under a two or three person tent, folds back under at the edges, and spends the rest of its life as a picnic mat, a shade tarp or a gear cover.
Buy the size that matches your tent floor, keep the edges tucked in, dry it before you store it, and it will quietly do its job for years.