Styrofoam Scraps Into Insulation Panels (Feb. 23, 2017 Update)




Introduction: Styrofoam Scraps Into Insulation Panels (Feb. 23, 2017 Update)

This project is inspired by the instructableof BaptisteL8, so, take a look at his approach on reusing cardboard scraps.

Despite experimental nature of the project and results that are still not that perfect, by following this directions you'll be able to produse fully usable product. And, the idea is to use cut-off pieces of styrofoam insulation boards that are too small to be applyed independently, to produce stiff insulating or light constructing panels by sandwiching the pieces between two layers of corrugated cardboard and using plaster as an adhesive.

As you can imagine the resulting product won't be the first grade one. This is not something you want to use in most of the rooms in your house, but it may work well in places, where look is not that important and final finish on the walls isn't required, like, for example: attic, garage, shed, or some sort of storage room. Although, I'll show two ways of finishing/decorating the boards I tryed.

I haven't used this panels at my home for any period of time, so I can't pedict how long they will last. I think they can hold for a long time, though, obviously, if conditions are dry.

Also make sure to read all the way to the end, there's some important updates over there.

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Step 1: The Materials

Three main components to make our pannels are next:

- Styrofoam scraps. Mine are 25mm thick cut-off pieces of bigger insulation pannels. I also tryed to incorporate packaging pieces cut into same thickness. This is a great source of the material, but it didn't work for me, because of reasons I'll explain in a little addendum at the end of this I'ble.

- Corrugated cardboard. It has some issues, like possible delamination due to absorbing moisture from plaster during the process (mine especially wasn't good at this, because I used some old pieces that were used as matting during the house renovations, and also were stored in dump conditions after that, so... yeah...). I have a couple of ideas on using different materials, but this is something I'll try later. Corrugated cardboard is what used in this project.

- Gypsum plaster. Mine was for finishing jobs, but this is not a dogma, it's just something I had lying around in suitable quantities. Experiment a bit and find what works best for you.

Step 2: Preparing the Plaster

Prepare the plaster. You want it to be easily spreadable but yet it should be able to keep the shape.

Step 3: Applying the Plaster

Lay down one of your cardboard sheats. When cutting it into size, add 2cm or so to every side for further trimming. My dimentions here are purely random because I'm not aiming for any speciffic pannel size.

Apply the plaster and spread it evenly with spattle. I used then toothed spattle to make sure I'm getting controlable amount of the plaster on the surface. It also helps for the styrofoam pieces to adhere.

Step 4: Placing the Scraps

Start putting styrofoam pieces onto prepared surface. Try to avoid gaps and creating gap lines that go across all piece (at least in one direction). Push pieces down a little to settle their possition.

If you're OCD person, it's your time.

Also you can fill the gaps with plaster. I used left-overs of mine to do so (after the photos were made).

Step 5: Sandwiching It Up (or Down)

Apply plaster to the second cardboard piece. Put it ontop of styrofoam layer of previous one, and put something flat along with something heavy ontop of our sandwich.

Leave it like this for a couple of hours.

Step 6:

It's enough to keep the panel under the weight for 2-3 hours (at least it was in my case). After that it's still not completly dry, but it holds its shape good enough to be dryed in this state to prevent the cardboard from oversoaking. It may take a day or so for it to dry completly.

Step 7: Trimming the Edges

When the panel is dry and the plaster is hardened, we can trim the edges. It can be done with a knife or a handsaw, but I find out a jigsaw works best for me. And it is preferable in this case (as my practice showed) to use the saw blade that cuts on the back (pull) stroke: it delaminates the edge of the cardboard less. Keeping the edge of the panel closer and tighter to the tables edge may help too.

Also it makes sense to use a pattern to mark the edges if you're producing a large quantity of panels.

Step 8: Decorating/Finishing

From this point I'm showing different panel: the first prototype I made earlier (I was able to use it while the other was drying). It's just the same, only with different dimentions, and a cardboard holds better. And this is the part, where I'm showing the two methods of decorating/finishing the panel I told about at the beginning.

As you, probably, can understand the corrugated cardboard presents not the most durable surface to work with. You can not spread a layer of plaster all over it and expect that it won't peal off all at once a year later. It is what it is, but it can be improved visually and practically a little bit

On photos you can see one side of the panel painted in couple of layers of water based wall paint. It holds well. The other side I glued with newspapers using some wallpaper glue leftowers. It also holds well. So after covering your walls with pannels you can cover them with newspapers to seal the gaps and then paint (or do just one thing).

Step 9: Testing#1

Because of two layers of plaster the panel is pretty stiff. It holds its own weight. It holds ~12 kilo (on two other pictures), even despite flimsy cardboard. I definitly could put more weight, but it was enoug for me (actually I was too lazy to look for heavy objects with known weight). The distance between supports is 60cm, and the width of the panel is 35cm.

Step 10: Testing#2

Also I decided to test how well the panel holds screws. I used 6 drywall screws to attach 2 wooden planks (approx 45 cm between them). I was surprised that screws didn't went right through the panel. I was able to firmly attach the planks with screw heads staying on the surface. Then I susspended the pannel on those planks and added weight. ~15 kilo this time, and I was feeling like I still had enough of strenght in reserve.

Step 11: Conclusion

Although there's a lot of possible improvements and tinkerings can be done to increse the quality of the product, I'm feeling like I'm happy with the results of this experiment. I believe you can decide for yourself what can be done with this technic and what it's worth. If you have any thoughts and ideas, share them.

Also I'm thinking to experiment a bit in next directions:

- Use some sort of one layer crafting cardboard/paper instead of corrugated cardboard.

- Use just a layer of plaster with arming grid instead of any cardboard (by spreading it on film and then removing it).

- Use the styrofoam itself as an adhesive, by spraying acetone on it's surface, and using the melted layes as a glue.

- Replicate CONBOU BAMBOO material concept by using corrugated cardboard, paper tubes and plaster as an adhesive.

So, there's a lot of work to be done, but now thank you for your attention, and thank you for your attention.

Step 12: Fail Addendum

This is how I planned to start this project. I wanted to use this setup to cut packaging styrofoam pieces into 25mm thickness boards, and the tool I tryed to use is my version of Gregariouses Blade Runner. Although it works fine on thinner pieces these were too thick and too dence. The blade struggled too much with cutting and constantly tended to bend aside.

For me it was the only available non messy cutting option for these pieces so I decided to put it aside.

Step 13: Feb. 23, 2017 Update

After the panel dryed it became obvious that the cardboard delaminated too much (here, and in all other instances I'm meaning that it delaminated from itself but not from the plaster layer). So I decided to peal it off completely. I discovered then that the layer that was contacting with plaster adhered realy nicely, without air bubbles trapped underneath or any weakly adhered areas. I decided to go ahead and try to coat one side in plaster to create smooth finish and then paint it. It turned out wery well (except for the parts where I used some old plaster, that lost its properties; you can see some spots aren't painted throughly because it was pealing off). I applyed acrilic based primer for wall paint to the cardboard layer, but I'm sure it's not that neccessary. I sanded the plaster layer and used water based wall paint.

The panel is pretty rigid, but I won't recomend to punch it a fist. I believe it can be reiforsed with fiberglass mesh for further strenght improvement.

So concidering the results, I definitly recomend to use single layer of paper over the corrugated cardboard. You can get really high grade finish this way.

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    7 Discussions


    1 year ago

    I work in a hospital lab. We get tons of large, thick (1-2 inch) sheets of styrofoam all the time. Any supplies that has to be kept cold arrives in boxes insulated with this material (with dry ice inside) It just goes to the trash. I use it behind concrete block in my back yard. Holds back soil & allows for drainage. Ask someone working in a lab to save it for you.

    Put a large bare wire (like from a coat hanger) into a soldering gun. The heated wire will cut through styrofoam without the mess.


    Reply 3 years ago

    Styrofoam insulation.panels are sold at home stores, we used that, but corrugated cardboard made the wood stove glow bright red. Almost as scary as burning old tires!


    3 years ago

    thanks for this, it helps me alot that you included what did and didn't work.There are some areas of my van that are totally lacking in insulation, I had thought of getting a styrofoam panel, but there's the cost and I was concerned it might squeak. A variation on this could allow me to do a trial run

    Waldemar Sha
    Waldemar Sha

    Reply 3 years ago

    Plaster will not do in this case, I think it will crumble too soon under the vibrations. Let me know what you're used and how it worked, if you'll have an opportunity. And thank you for your reply.


    3 years ago

    I am impressed by your ingenuity. You not only found a good way to cut down on waste but you put it through a very good testing process.