So you bought a bed from IKEA, and now you have enough cardboard to build yourself a couch. A classic problem that we've all had. The obvious solution is to just build a couch*, and that's exactly what I'll do in this instructable. The seating device you see pictured here has stood up to not just one or two, but three adult men for an entire night of poker, and after three weeks it shows no signs of wear. Incredible.

*There's no back, so I guess it's more of a bench, but couch sounds so much nicer (and nobody has challenged me on the terminology).

Step 1: Supplies

This project requires a lot of

Tape (say, 2 rolls of packing tape, and 3 rolls of normal tape)
Glue (I used 7 bottles of white glue)
Scissors, box cutter, serrated knife
Flour (less than a cup, I'm not entirely sure this is necessary)
Weights (just any heavy objects to apply pressure while glue is drying. Soup cans, shampoo bottles, pasta sauce, metal box, gamecube, a chair, etc.)
Pencil, marker
Ruler
Cardboard (I recommend getting a queen sized mattress and bed frame from IKEA, for the cardboard)

(You may see these items pictured in the image above. Remember, always take pictures as you go!)

Note: odds are, you will have a different selection of cardboard than I did. This instructible isn't so much an exact instruction set as it is an example and a set of approaches to consider. Also, make sure to check out the pictures! It's tough to describe in text how certain oddly shaped bits of cardboard should be attached to one another.

Step 2: Design

Before building your couch you must design your couch. Slapping cardboard together William-Nilly will lead to suffering, as it will totally clash with your décor. You might also run out of cardboard if you don't plan where you'll put it.

A couch in its most basic form, as seen in the first diagram, consists of a bit where you sit, and a bit that touches the ground. The bit where you sit must be wide enough to fit all of your guests, deep enough that you are all comfortably supported, and strong enough to support all of the weight on it.

The bit that touches the ground supports the bit that you sit on, so it must be strong enough to support not only those seated, but also that little bit of cardboard up there. It's not much extra weight. This bit also determines how tall your couch is. Ideally it will be tall enough to be comfortable, but not so tall that it's weird! (I used a pre-built couch for reference).

One might naively assume a solid stack of cardboard is the most robust option. Quite strong, and dimensions are easily customized, but see figure 2! This is no couch, but a box!

Using what I had available, I concluded that a couch-top of 2 boxes (3rd image) and a support beam (4th image) was ideal, with 5 legs. The middle leg reduces the strain on the top of the box.

Step 3: Organize and Clean

Like they say, organized cardboard is happy cardboard, and happy cardboard makes happy couches! Don't you want a happy couch? (It's fine if you don't).

Organize your cardboard into piles of similar shape and size. This will help you take stock of available materials, which will help you decide where and how to use each piece.

Creased cardboard can be a convenient building material (see the second picture), or it can be annoying. I had multiple thin, wide, tall cardboard boxes that seemed more useful as strips and sheets of cardboard than as they were.

When cutting, keeping a slight crease in the cardboard helps the box cutter stay on a straight path. Always be careful though!

Step 4: The "Seats"

My mattress came with two cardboard end-caps that fold up to be one side short of a box. They're about long enough for a couch, but individually they aren't deep enough (deep meaning distance from front to back) - I have two though! Together, they form a nicely sized seating area.

Along the side of the mattress were two longer pieces of cardboard of a similar shape, but having only 3 sides instead of 5. Because of that, I imagine these would not be as strong as the caps, so I used them as reinforcement instead of the main support.

The longer pieces were cut down to fit inside the end-caps. Glue was applied like Jackson Pollock, the cut-down side pieces were wedged into place, and the cardboard was weighed down while the glue dried. The bottom was glued first, then the sides.

Step 5: The Support Beam

The first image shows the longest pieces of cardboard I had. It made sense to me that they should run the full length of the couch (instead of cutting them into pieces to use another way). I only had one of each, so it seemed best to use them in the middle, as opposed to the front or back.

Conveniently, one piece fit inside the other! I filled the empty space in the white shape by padding the sides of the larger piece of cardboard with strips I had cut from some of the boxes. After making sure everything fit snugly, I removed the pieces, drizzled them with glue, and stuck it all back together. I placed it on the floor (on another piece of cardboard - to protect the floor from glue) and weighed it down while the glue dried.

Finally, I used a saw on a multi-tool to cut the beam to the length of my front and rear seat boxes.

Regarding that thick piece of cardboard: inside it's like a honeycomb, with hexagons tesselated across the wider face. It can take a lot of force in the shorter direction, in either of the other directions, well...it's pretty easy to crush. We aren't worried about crushing though, we're worried about buckling. Just because of its dimensions, if anything, it's more resistant to buckling if force is applied to its edge (that is, the thinner side).

Step 6: Putting It Together

Not "putting it all together," just putting together what we have so far. (The legs come later).

We have two "seats" and a support beam to go between them. Rather than sitting directly on these parts, I made a top surface from a sheet of cardboard (two actually, one wasn't large enough). This helps resist front-to-back forces, which nominally there shouldn't be much of, and distributes the load to some extent. (I'm not sure if that extent is considerable).

Really though, it just made sense to me, and I think it looks nice.

I taped the cardboard that would become the top end-to-end to get enough length, then trimmed them to the appropriate width. Then it was just a matter of gluing down the seats and beam.

Step 7: The Legs

This is the step where we make the legs!

I had a tall square box that happened to be the perfect size to wedge inside the 'seats.' I cut off each end (with a middle piece left over), basing the height to cut at on other seating devices in my house. I glued the end flaps shut, and that was 2 of 5 legs.

From those 'seat reinforcements' (the 3 sided cardboard), I had some leftover material. These nicely folded into triangles, and looked like they would make good legs. I taped these pieces along their mating edge to form triangles, then cut them to the appropriate height, and glued along the edge of the created leg.

...but cutting them to height left me with a bit of extra cardboard! I glued these into the square legs as a diagonal support at the top. This provides some support against bowing outward, and helps distribute vertical pressure above the center of the leg.

At this point I had 4 legs, which I neglected to take a picture of.

Step 8: Additional Support

Call me crazy, but I wasn't sure this cardboard would be able to support my weight, while also supporting all of my closest friends, and we would have to be very close to all fit on this couch.

I still had a lot of unused cardboard, and I figure, if a couch made from some of the cardboard is strong, a couch made from all of it will be even stronger.

1. The Big Pieces

My greatest worry was that the couch would buckle in the middle along its length, so I wanted to add more vertically oriented cardboard parallel with the front. I cut some of the large sheets so they would fit inside the 'seats,' adding another layer of reinforcement. Then I added yet another! (Albeit, a shorter one this time. I was running out of cardboard). I only added these supports to the outside - the front and back - panels. Not the middle; I'll leave that support to the support beam.

2. The Triangle Pieces

Remember the triangle legs? There's still leftover material! Using a sheet of notebook paper as a measuring instrument, I cut two pieces of the extra material to fit inside the seats. I placed this support in the middle of the seat(s) (lengthwise) to protect against the front and back bowing out, or collapsing in when someone inevitably pushes their legs against it. I glued additional strips of cardboard over them to ensure the mating edges would stay together, and increase the adhesion to the seat's underside.

3. The Weird Pieces

Considering the number of these pieces I had, I decided to use them for two things. First, additional material in the area of the support beam, and second, under the 'seats' to support against vertical and front-to-back forces. I stacked up what was available, and glued it in place.

Step 9: Additional Pylons

Here we'll attach all 5 legs and add support to them.

Remember that extra section of square cardboard box? Who could forget it!

That's going to be the 5th, center leg. Because it's going under the support beam, it will need to be notched out. It also needs notches to fit onto the triangle-shaped supports. I had some identical pieces of thick cardboard that, by chance, fit perfectly inside the square piece, so I placed them inside it for additional support.

I then glued the other legs into place in the 4 corners, and started adding supports to the legs.

I glued extra cardboard panels to the square legs, but focused more on the triangles because of their 3 sides and no bottoms, compared to the square legs' 4 sides and closed bottom. This was more about 'what fits?' than a thoughtfully executed plan.

Step 10: Even More Support

There's still cardboard??? Well, glue it together (because layers are good), and glue it into the couch!

Step 11: Douse It

With glue. Lots of glue.

I wanted to soak the cardboard with glue to strengthen it, like paper mache, so like paper mache, I added some water and flour to the glue.

Step 12: Tape It

After the glue dried, I wrapped the top and sides (but not the legs) in packing tape. This provides some protection against spills and scratches.

Step 13: Use It!

Well, the glue's dry, right? And all of the cardboard (more or less) has been used?

All that's left to do is take a seat. Oh, and cover it with something nice. Not that nice, but nicer than cardboard. Honestly, I was shocked to find out putting a comforter on this thing fools people into thinking it's real furniture (really, it does), but at the same time, who would ever assume this thing was cardboard?

On a final note - the top surface of this is incredibly firm. It doesn't feel quite as firm as wood would, but it's much harder that people expect cardboard to be.