tarps come in many types of material and construction with differing strength, weight and cost. A lot depends on whether you want to stationary camp or hike mountains and throw up a shelter at the end of the day. Obviously, weight would be a large factor in deciding. Cost is a major factor.
the main types:
1 polythene tarps. cheap and not too strong. Usually available from hardware stores and have mundane uses such as wood pile covers, and boat covers. A 3x3 medium weight plastic tarp will probably weigh 4-500 grams, but when folded is bulky compared with "camping" tarps. Usually have grommets around the edges to attach tie outs or insert pegs. These are IMO a weak point and will eventually fail. I would however point out that I use such tarps as a boat cover on the road trailer, and they have survived a number of seasons of 70 mph (120 kph) dashes to the coast without serious damage. find one in subdued green or brown and they give an adequate, inexpensive shelter for the impecunious.
2 Polyurethane (PU) coated nylon. An example is the DD 3x3 recommended here. About the same weight as the plastic tarp, but more durable. Many have grommets for tie downs etc and IMO are weaker than those using cloth loop tie outs around the edge, and even along the ridge line.
3 Silnylon. This silicone impregnated nylon (opposed to coated as in 2). lighter and much more expensive than PU coated. The main benefit compared with 1 and 2 is lighter weight, which would be important if you backpack/hike a lot.
4 Cuben Horrendously expensive, extremely lightweight, and pack away to very little. Use reports indicate that they are rather fragile compared with 1 2 and 3. Definitely have by far the greatest cool factor.
5 DIY for the poverty stricken student, this is a great option to practice skills and get an inexpensive shelter. Polythene painters drop cloths or secondary window glazing film reinforced with Gorilla tape, duct tape and postal parcel wrapping tape are the main options. Here are a couple of videos to illustrate:
http://www.youtube.com/watch?v=FgCUc_aUnb0
http://www.youtube.com/watch?v=FgCUc_aUnb0
These show what can be achieved with a little skill and imagination. If you want more privacy, use opaque plastic film.
These plastic film tarps are not the strongest, in particular are weak in respect of punctures. With a bit of care in location, set up and weather orientation they will be adequate for summer lowland shelter.
So USD 10 or so for DIY through 3-400 for cuben (plus VAT)
BTW, none of these polythene, nylon, cuben tarps should be used anywhere near a fire, sparks will create holes in no time flat.
Cotton tarps are, for the backpacker,horrendously heavy, and fairly expensive.
go to your hardware store and examine carefully the materials and tarps on offer. Also go to your local outdoor eqiupment store and see just what features are available (e.g. grommets vs tie outs, silnylon vs PU coated. Draw up a cost v feature/benefit chart and see what best meets your needs and(more important) budget.
