What to Look For
Today's tents are lightweight, portable and pricey. Though many are manufactured with ground sheets sewn into the flooring, moisture and dirt can still seep through the weave; and sticks and rocks, common in the wilderness can puncture even the most durable fabric. Purchasing an additional laminated ground sheet, one impervious to water and dirt, punctures and formic acid--a secretion of ants--will extend the life of your tent. Choose materials that have a high hydrostatic head value and that are laminated with three to four layers of "silconizing" material.
Choose a ground sheet that fits your tent, aligns with the tent's grommets and fits securely like a footprint. While purchasing any type of ground cover might seem reasonable, unless it forms a secure fit against your own tent's floor, it can shift, trapping moisture and dirt. In addition, use a ground sheet only under the tent. Some like DuPont's Tyvek have a slick surface and using it as a campsite ground cover or within the tent can cause falls.
If moisture and dirt are a problem in your tent, choose a ground sheet with a high hydrostatic head, which is a comparative measure of waterproof fabrics used by the industry ranging from 1,000 up to 8,000. High-quality tent manufacturers publish their measures. For ground sheets, a reasonable number is greater than 3,000.
Where to Buy
Vaude, a German camping supplies manufacturer uses double-sided "silconized" (3 to 4 layer silconizing) 40D polyamide ripstop fabric with a hydrostatic head waterproof rating of at least 3,000 mm. Higher ratings between 6,000 and 7,000 are available. Their ground sheets are water- and formic-acid resistant and despite their light weight, are durable.
U.S. retailers like Go Fast and Light, a camping supply site that specializes in durable yet light-weight camping equipment carry Vaude gear. Much of the line is carried through camping Web sites in the United Kingdom, but sold internationally. Tuckerman Outfitters in Portsmouth, New Hampshire also sells a variety of 0.6-millimeter laminated polyethylene ground sheets ranging in size from small rectangular to extra-large multiroom. Although it doesn't state that the ground sheets are resistant to ants and formic acid, any double-laminated impervious ground sheet will serve you better than one that's not double laminated.
Based on September 2010 prices, DuPont's Tyvek ground sheet was moderately priced at $29. However, it only comes in 8 feet by 10 feet, which makes it less adaptable to various tent shapes and sizes. Essentially, it's marketed as a ground sheet, but it's more of a one-sheet-fits-many-needs type of product. Rock Creek's ground sheets, ranging in price from $31 to $60; but most, described as "Footprints" are made for specific tent styles. Before you buy from them, you should confirm that they have the ground sheet that matches your tent. Tuckerman Outfitters, for the price--$12 to $35--offers a high-quality, durable product that fits most tent designs. If you want Vaude's ground sheet, Cotswold Outdoors in the U.K. sells them from 15 to 30 Pounds which is approximately $30 to $60 (dependent upon exchange rate).
According to Go Fast and Light, a camping Web site that supplies durable yet light camping equipment, hydrostatic head is a measure used by the fabric industry to rate waterproof fabrics. In order to determine hydrostatic head, a column of water is pressed against a fabric. The column height is increased until water leaks through. Different conditions require different levels of protection. While a raincoat requires one level of water protection, a tent ground sheet, subject to pressure from foot traffic requires a higher degree of protection.