Ultralight Groundsheet for Fastpacking: 18 g/m²
On a fastpacking trip, every gram needs a job. A groundsheet has one clear purpose: it separates a tent floor, sleeping pad or bivy sack from wet, abrasive ground. XFOIL is a waterproof, plasticizer-free polyolefin film at 18 g/m² and 19 microns.
The XFOIL sheet is 1.6 × 2.4 m and weighs 67 g. Cut it to the footprint you actually use – no more. View XFOIL 1.6 × 2.4 m.
What the groundsheet does – and does not do
Under a tent, it keeps ground moisture away from the floor and reduces abrasion on the bathtub floor.
Under a tarp or when bivying, it sits below the sleeping pad and bivy sack. Your quilt sits above them; the sheet does not replace a bivy sack.
It is not a sleeping pad. Insulation and comfort still come from your pad.
Choose the campsite carefully. Remove thorns, sharp stones and roots before laying out your system. A thin groundsheet supports good site selection; it does not replace it.
Cutting the right size
There is no universal size. Measure the area that actually touches the ground, then cut to that shape. At 18 g/m², 84 × 210 cm weighs about 32 g: a calculation for a narrow one-person setup, not a rule for every tent.
Solo and trekking-pole tents
Follow the bathtub floor, not the outer tent dimensions. The sheet should remain inside every edge. With a trapezoid trekking-pole tent, trim the sheet to the floor shape instead of leaving a large rectangle protruding; exposed edges can channel water between the sheet and tent floor.
Tarps and bivy sacks
Under a tarp or with a bivy sack, one simple rectangular sheet below the pad is enough. Add only the head and foot allowance your bivy sack and sleeping position need. You do not need seams, grommets or extra components for this use.
How to set it up
Set up your tent, tarp or sleep system once on level ground.
For a tent, mark the bathtub floor; for a tarp or bivy sack, mark the pad and the allowance you need.
Cut a smooth edge and lay the sheet out before each trip.
At camp, clear sharp objects before the sheet and sleep system touch the ground.
Quick decision
Sleeping in a tent: cut the sheet slightly smaller than the bathtub floor.
Sleeping under a tarp or in a bivy sack: use a rectangle below the pad and bivy sack.
Reducing weight: calculate area × 18 g/m² instead of choosing a size by feel.
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