By laminating sheets of cardboard together into a large block and cutting this up with a table, or circular saw, you can create cardboard lumber of any dimensions you want: 2x4s, 2x8s, 4x4s. If you alternate the grain of the corrugations you can create plywood. If you glue your lumber together end-to-end you can create strong honeycomb-like boards.
You will only need three things to create cardboard lumber:
1) A Saw
2) Lots of cardboard
3) Glue... lots of glue
Step 1: Types of Saws
Circular Saw: If you're really good at cutting straight lines and have no other option then I guess you could give it a try.
Hand Saw: Possible, but too labor intensive for me.
Band Saw: If your band saw is as powerful as a circular saw than go for it, this could open interesting options.
Chain Saw: Messy...
No Saw: Unfortunately for people without access to saws, this instructable is not for you. I know it looks cool and all, but it's just not gonna work out.
Step 2: How to Get Cardboard
Save up cardboard from boxes your family uses. You'll be surprised how fast it adds up.
Go around town and ask any businesses if they have any cardboard you could take. It will likely be already broken down for you.
Super moral and Mostly legal free cardboard:
If you're in a hurry, or just lazy, you can drive around the back of stores and look through their recycling dumpsters for cardboard. Be warned though that dumpster diving is a crime, but most people will be fine with you hauling away some of their trash.
Maybe legal and moral free plastic cardboard:
Those corrugated plastic advertising and campaign signs scattered around your neighborhood are considered litter/unclaimed property in *some* areas. Snatch a bunch of them up fast and you'll have an awesome start to rock solid, corrugated plastic lumber (Be sure to use glue designed for plastic though. Wheatpaste won't work.)
Most of my cardboard came from my school cafeteria and my family's recycle.
Step 3: Prepare the Cardboard
You have to cut your cardboard so that each single layer lays flat, and is completely filled with cardboard. The look and strength of your lumber will all depend on how well you cut your cardboard layers up. It would be best to have all cardboard meet at hard, squared off corners.
To prepare your raw cardboard boxes, you have to cut all of them into flat rectangles, removing all tape and anything you can to make them just cardboard rectangles.
Step 4: Stack the Cardboard
Now is a good time to estimate the sq. ft. of cardboard and see how much you can build.
Step 5: Get Some Glue
Wheatpaste: At less than a buck a gallon, this is what I will be using. You can view my wheatpaste instructable here, or basically heat 1:4 part flour/water until it get's thick. Wheatpaste, when made properly and applied correctly will be pretty much as strong as the glue that holds the corrugations of the cardboard together (they use a starch glue, white flour is starch...). It's used by paper machers and also graffiti artists to post paper pictures to concrete walls and create a rock hard irremovable poster. I would recommend adding any bacteria deterrents you have (see instructable).
1:1 Wood Glue: You might be able to find a gallon of wood glue at your local hardware store for about $10 if you're lucky. This should be diluted with water 1:1 because we're covering such a large area, and only want a thin coat, and also to help the glue soak into the cardboard. This comes out to $5 per gallon. The advantages of this is it's much stronger, the corrugations will always rip before the wood glue seams, and is easier to make and apply (but not much). After doing this with wheatpaste, I would recommend this way, simply because the wheatpaste is not as sticky as it needs to be.
Note: You could also use Wallpaper paste I guess; it comes in a powder at the hardware store.
You will need a minimum 2 gallons of either to properly glue the amount of cardboard I am doing.
Step 6: Glue!
My 4x8ish block was a little thin, so I cut it down the middle and doubled it up.
Step 7: Wait...
Step 8: Cut!
Then I used a table saw to cut everything into 1.5" strips. I would highly recommend a partner to help you cut up the block. It's heavy and unwieldy.
Step 9: Honeycomb Plywood
Step 10: Build!!!
To further strengthen your projects, you can seal the whole thing in wheatpaste like i did in the previous step.
Ideas for using this stuff, suggest anything you want to add:
Scapile (my original inspiration for all of this)
A cardboard playhouse made by Piersg
a MASSIVE amount of completed woodwork projects (search with the "view more tags" link)
lots of lumber plan blueprints
Andy Lee coffee table
nice table design
cool sitting bench
snap together table from instructables
Please rate and comment...
Can we stop talking about the environment guys? I wasen't really trying to make any point that this would help the environment anywhere in my instructable. If you have easy access to cardboard, flour and power tools, then you might be interested in making this. Go ahead, try it and tell us what happened. If you don't like this idea, then please suggest better alternatives. Please calm down the comments on your assumptions about how cardboard and wheatpaste effect the environment.