I use the term tarp here to refer to any sort of floorless shelter. These come in many shapes and sizes, from a basic rectangle of nylon to the complicated geometry of a pyramid tarp. The pyramid tarp (or 'mid) was popularized by Black Diamond's Megamid and Betamid. Many companies now make similar shelters including MSR, Integral Designs, GoLite, Mountain Laurel Designs, Tarptent, and Brooks Range. The standard mid design is as weather and storm resistant as most tents.
One type of psuedo-floorless shelter is what many companies call "fast-pitching". This is a configuration some tents are capable of where the tent is pitched with the groundsheet, poles, and fly but no tent body. Generally, the weight savings are low and these set-ups aren't particularly stable or weatherproof. One exception are Hilleberg tents. Their tent design has the poles attached to the fly instead of the tent body and allows you to pitch the fly like a tarp.
The first and most obvious benefit of using a tarp is that it weighs a lot less than a tent. I have been using the Black Diamond Beta Light almost exclusively from late spring through late fall for several years. It weighs 1lb 8 oz (680g) and has 34.7 square feet of livable space with about 15 more square feet of covered space for storage. Let’s compare this to a reasonably light two-person tent, the Big Agnes Fly Creek UL2. It weighs in at 2lb 10oz (1190g) has 28 square feet of usable space and a 7 square foot vestibule. So it weighs almost twice as much, but offers less useable space or storage!
The second biggest benefit you get from using a tarp is that it takes up less space in your pack than a tent. The Beta Light fits in a 6" x 4" stuff sack, the Fly Creek UL 6" x 19". The tent takes up 4 times as much space as the tarp. Keep in mind that this is a fairly light and compact tent!
|From L to R: Black Diamond Beta Light and Mega Light tarps, Firstlight and Skylight tents, Hilleberg Nallo 2, Mountain Hardware Trango 2. The Trango 2 is about 7 times heavier than the Beta Light. An old Petzl Elios helmet provides some scale.
One of the ways tarps can be so light is that most don't come with poles. You use your trekking poles to set them up. This is advantageous because trekking poles are much stronger than the poles that come with tents.
A tarp also has some subtle "quality-of-life" advantages over a tent. When camping on snow you can easily customize the "floor" to suit your needs. Because there is no fabric floor and the walls don't have to touch the ground, using a stove inside the tarp is less risky. When cooking in a tarp it's harder to accidentally melt part of your shelter and the superior ventilation lessens the danger of carbon monoxide accumulation. It should be noted that all manufacturers of tents, tarps, and stoves expressly warn the user to never cook inside their shelter.
|The Black Diamond Mega Light in the High Sierra. This four person shelter weighs 2lbs 5oz (1005g) and is a palace for one person. Photo by Jessica Haist.
Tarps are not always as intuitive to set up as tents. Like tents, some are easier than others are. The additional thought you'll have to invest in understanding and setting up your tarp is more than paid off in a lighter and smaller pack. I can usually set up my Betamid faster than the average climber can set up their shelter. In their defense, I have had a lot of practice.
Aggressive bugs can be a big drawback of using a tarp. You've got two options to deal with them. The first is how it's set-up. Pitch the tarp so that the edges are on the ground and pin the edges to the ground with rocks, creating a reasonable seal between the fabric and the earth. The second solution is to use some kind of bug tent or netting arrangement inside the tarp. Some manufacturers make bug tents designed specifically to go with their tarps, many more make some sort of bug bivy sack.
Tarps accumulate just as much condensation as tents, but lack the inner tent body to keep the user away from it. MSR put together a great video on tent condensation and how to manage it. Please see the video below:
--Ian McEleney, Instructor and Guide
--Ian McEleney, Instructor and Guide