There are a bunch of posts on Tent Ground Cloths. They're all pretty easy to make, just as this one is.
Then why another DIY ground cloth making post or in this case Instrucructable one might ask?
My answer is simple, because there seems to be plenty of confusion about tent ground cloths, mainly the primary purpose of a tent ground cloth. With out knowing the primary purpose, you can't make one correctly, now can you?
Somewhere along the line, the primary purpose got lost. And I don't care what anyone tells you, what company makes what claim. The primary purpose of your ground cloth is simply to help protect your tent floor from sticks and stones and punctures. It is not to weatherproof your tent floor. It should already be weatherproofed. If not, that's anther issue you have all together. And should be remedied before your next outing.
That's not to say you can't add additional waterproofing to your ground cloth. Of course you can. But it must be limited to the floor dimensions. Preferably the waterproofing on the ground cloth should be your tent floor dimensions less an inch boundary all the way around the floor perimeter.
That said, your "ground cloth" can be as big as you want it to be. It should allow water to run through it, not soak up water, dry quickly and help protect your tent floor from the elements on the ground. Which you hopefully swept and cleared the area you plan to pitch your tent of all: Sticks, Twigs, Rocks, Logs, Stones and other things you might be uncomfortable lying on.
You can have a ground cloth 10 feet by 20 feet large with a tent only 3 foot by 7 foot if you like. But If the whole thing is water proof, guess what? First rain, your tent and everything else on it, will be sitting in water. And that is not what you want. Well, I don't, maybe you do...?
Hopefully you have a clear understanding of what your ground cloth's purpose is for. Lets make a simple yet effective one.
The material you use for your ground cloth is up to you. You could just throw a sheet down and call it a day. If you know it's not going to rain, and the ground isn't wet or water logged. That is a fine and viable solution. But lets make one for all weather conditions that is even lighter weight than a bed sheet.
I have used in the past Pond Under Liner. It is designed for the same purpose as our ground cloth needs. To help protect the rubber pond liner from punctures from sticks and stones and the like. It works well. Depending on what type material it is made from, it will not retain water and dries quickly.
However, I found another product recently that worked great. It's a Landscape Fabric used to keep weeds from growing made from recycled plastic bottles. It's very light weight. durable (has a 25 year warranty), flexible, no noise like you get from some products (Tyvek or tarps or heavy plastics as I've seen some people use). And because it's made from plastic bottles, it doesn't soak up water and it dries very quickly. It;s light green in color which proved very plesant on the feet when I was making it on the stone patio on a incredibly hot humid Florida day at noon.
It's made or put out by Sta-Green and you can find it at Lowes for $10 a roll at the time of this writing.
So lets get all the materials and tools together for the build:
1 3x24ft roll of Sta-Green Landscape Fabric - (depending on the size of your tent - if you need more - get more)
A Grommet Kit - Preferably you'll use non rusting or Aluminum Grommets. Use ones with 3/8 to 1/2 holes if you want to stake it out.
Heat Shrink Tape or Duct Tape (2" width) Only if you need a double width of landscape fabric or want to add a water proofing layer
or if you prefer you can sew the seams, for that you'll need or have access to a Sewing Machine.
4mm Visqueen or the like plastic sheeting ( only if you want to add a water proof layer to your ground cloth).
Scissors or Utility Knife. ( to cut the landscape fabric and plastic sheeting.