How to Build a Cooler out of Foam Board

[You can also watch the video tutorial posted on my YouTube channel and/or view this photo album]

I would love to have one of the modern high-performance coolers, such as the rotomolded style, but we don’t actually need one badly enough to justify spending the money. But I wondered if I could build something comparable out of foam board for a fraction of the cost. 

So I built a small prototype, process described below, and here’s what I learned. I could NOT build a comparable cooler at a fraction of the cost. Nonetheless, I had a ton of fun and while the example I built would not stand up to the “Yeti” style coolers, it is quite functional and looks pretty great, IMHO. 

I started with a two foot square section of one-inch foam board. Note that for a larger build, I would use two-inch foam board. 

I cut five pieces out of the foam board as follows:

1 @ 9x14”

2 @ 7x14”

2 @ 7x7”

Those dimensions are approximate, so be wary of using that as a cut list if you are foolish enough to follow my example. I used an electric jigsaw with a fine toothed blade to cut the pieces. It worked reasonably well. The edges were square, although just a bit rough and it created a lot of particles. It’s possible to buy a jigsaw blade specifically for foam board that I’m certain would work much better. 

It may have occurred to you that my cut list consists of five pieces, whereas a box has six sides. Turns out, with a two foot square section of foam board, there’s not enough material for a bottom AND a lid. I chose the bottom, as I felt keeping the ice from falling out was more important than keeping my rootbeer hidden from the Park Rangers. 

I then applied Gorilla Glue to the edges of the pieces and clamped them together. 

Since foamboard is not super durable, I wanted to cover the interior and exterior with a protective layer. I used foil tape on the interior sides. I think that’s a good solution for a cooler that will hold food and beverages for a picnic or camping trip, but probably not durable enough for a fish box. For a fish box, maybe multiple layers of foil tape would work.

I did want the inside bottom to be more durable, so I cut a piece of thin plywood (i.e. luan) to cover it. I covered the luan with foil tape and glued it to the inside bottom. 

There was a gap on the inside between the bottom luan and the sides, which I filled with polyurethane sealant.

I also glued a piece of luan to the outside bottom, and applied a couple coats of polyurethane.

For the lid, I cut another piece of luan. I then cut a scrap piece of styrofoam (maybe ½ inch thick) that was just big enough to fit between the walls. I then glued the styrofoam to the underside of the luan lid. I covered the whole assembly with foil tape. For a lid gasket, I applied double-sided foam tape around the rim of the lid. I covered the exposed side of the 2-sided tape with electrical tape so that the cooler wouldn’t seal shut the first time I tried the lid. 

Some type of rubber weather stripping material might work better as a gasket, but I was trying to mostly use materials on hand.

To protect the exterior sides, I used a scrap piece of countertop laminate. I cut a piece to cover each side and glued them in place. 

I trimmed out the bottom and side edges with corner molding. I used wood to trim out the top (also glued in place) so I would have an attachment point for lid hinges and handles.

The handles are painted PVC (1 inch, schedule 40, if memory serves). I cut four small strips of leather (about ½ by 1 inch) and attached two to each side with two screws each. This provided a couple of loops on each side to attach the handles. I ran a piece of paracord through the piece of PVC handle and tied the ends to the leather loops. 

For the hinge, I screwed a short section of nylon webbing to the lid and to the wooden trim around the edge. 

For the “opening’ handle, I drilled two small holes in the lid and tied in a loop of very thin paracord. I then tied a 2.5 inch piece of paracord to the thin paracord loop, just big enough to grab and open the lid.

The paracord loop also doubles as part of the latching mechanism, the other parts being the receiver end of a slide lock and a cotter pin.

The result looks good, keeps things cool and is reasonably sturdy. I wouldn’t hesitate to take it into the wild, but would be careful not to abuse it. 

My only out-of-pocket expense was about $30 for the foam board, foil tape, glue and corner molding. All the other pieces, materials, fasteners and supplies were things I had on hand. If I had needed to buy every single item, the cost would be ridiculously expensive.

Speaking of ridiculous, I spent a ridiculous amount of time building it. However, I was unfamiliar with the materials as well as the gluing technique. Further, I spent half the time looking for things I KNEW I had on hand, like paracord, pieces of PVC, polyurethane sealant and the right size screws. It’s time to organize all my crap, I mean valuable supplies. 

In a build like this, there’s a compromise between lightness, durability and low cost. You probably have to pick two. 

If money was no object, or if I needed to emphasize durability, for the outer covering I would probably use a durable wall paneling material made of some type of plastic or vinyl. I think they use it in shower stalls, commercial kitchens, etc. As of this writing, it’s available in four by eight foot sheets from the large DIY/home improvement store near me.

Here’s the bottom line: lf you just need a good cooler, go buy one. But if, like me, you love making things or need something of a custom size, then I think it’s a fun project to tackle.