How to Make Papercrete Blocks


Never heard of it? Go here.

Up to speed?

Great, Let’s get going.


Papercrete mixer

Block molds (mine are made from 2x6s and scrap siding)




Paper (used of course)

Shredded plastic (if you want)

95 lb bag of cement (cement not concrete- no rocks or sand in the mix)


Emtpty papercrete molds

1.  Set out your molds.  You will need enough flat space to drive over them and pull your truck and the mixer in all the way front of the molds.

Filling papercrete mixer with water

2.  Fill the mixer 3/4 full with water.   I just eyeball it.

papercrete mixer filled with paper

3. Put in the paper/plastic.  I use about 75 lbs.

adding cement to papercrete mixer

4.  Add the bag of cement.  You don’t need to open it,  just toss it in.

covered papercrete mixer

5.  Cover the mixer securely.  This is very important.  Just think of what happens when you have a blender top malfunction and multiply it by 100…  I use a canvas tarp with a cargo strap.

papercrete slurry

6.  Drive slowly- 5-10 mph for one mile.  The mixer will chop up the paper into a pulp and mix it with the water and cement.

emptying the papercrete mixer

7.  Empty the slurry into the molds.  If you got the mix right you should be able to open the drain, fill some blocks, close it, pull forwards a bit, repeat.  If the papercrete is too thick there’s some shoveling in your near future.  Sometimes I use a plunger to force it through too.  I get about 45 blocks per batch.

papercrete blocks in molds

8.  Remove the molds.  I do this right away.  I want as much air flow as possible.

papercrete blocks

9.  Wait a few days for the blocks to dry.

pile of papercrete blocks

10.  Stack the blocks under cover to dry further.  I like to wait a couple weeks before using them.

11.  Do it again and again until you have several pallets stacked with bricks and your year’s supply of paper trash is gone.  That’s 10-15 batches for me.  I usually have to go to the recycling center to pick up more paper to boot.

Now go make something cool and send us a picture.

Next time:  building with papercrete blocks.

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  1. Najam Ashraf
    Posted February 20, 2012 at 10:30 am | Permalink

    Very easy instructions.I’ll start with the blocks first.

  2. padre
    Posted March 23, 2015 at 10:25 pm | Permalink

    Are they more or less Buller resistant than a plain old concrete block? I would bet more, but I am wondering if you have ever taken them to the range for a comparison.

    • Mike
      Posted March 25, 2015 at 6:14 am | Permalink

      Never tried that test.

  3. Chris
    Posted March 25, 2015 at 1:01 am | Permalink

    this looks like a great idea, but I have several question.
    first, where did you get the mixer?
    second, once dried how weather resistant are they?
    third should they be kiln dried or baked?
    forth, how structurally strong are they, can they be used for walls or footers?

  4. elizabeth sandvick
    Posted August 18, 2015 at 10:53 am | Permalink

    where do I get one of your mixers ? thank you

    • Mike
      Posted August 18, 2015 at 11:23 am | Permalink

      If you want a tow mixer you have to make one which is a big barrier to entry for getting started. You can use an electric drill with a paint or plaster mixer and a 5 gallon bucket to do small batches in. I have instructions on all things papercrete here:

  5. Mini Kitten
    Posted August 23, 2015 at 1:34 pm | Permalink

    It’s extremely interesting. 🙂

    Did you try to use only plastic shred ?

    And if so, is this “plasticrete” more or less prone to suck moisture as papercrete ?

    If not, which are differences btw paper only papercrete and plastic and paper papercrete ?

    • Mike
      Posted August 25, 2015 at 12:17 pm | Permalink

      You need the paper fibers to hold everything together & provide the airspace for insulation. Plastic only works as a filler. I don’t use more than 10%

      • Mini Kitten
        Posted August 26, 2015 at 9:45 am | Permalink

        Many thanks for your precision 🙂

        There are also ppl who seems to consider plastic as more than a filler :

        Maybe their technics are different ?

        Your insight is very interesting

        • Mike
          Posted September 1, 2015 at 5:02 pm | Permalink

          Your point is well taken.

          Here is a very long explanation to your original question. Read on for a didactic ramble on concrete / papercrete.

          All concrete, papercrete included, is made from a combination of Portland Cement and additives, usually aggregate. Aggregate is generally a mixture of sand and gravel. The sand and gravel are filler and the cement binds them together. The idea is to fill the void where the concrete is going with mostly larger rocks or gravel (the cheapest material) then fill the spaces between the gravel with sand (the second cheapest material) and bind it all together with a matrix of cement (much more expensive than sand and gravel). Steel reinforcing is also usually added because concrete has a high compression strength but a poor shear strength. The steel is by far the most expensive component. The ratio of sand, gravel, cement and steel can be adjusted to make it stronger for a foundation or smoother for a concrete countertop etc. There are other additives that can be added to concrete but those are the fundamentals.

          The first article you linked to showed an example of shredded plastic being used as a replacement for steel rebar. I can’t speak to the reliability of the method but the idea is that having lots of little strands of plastic will cumulatively equal the strength of the steel. In the other article crushed plastic was being used as the sole aggregate. It’s not surprising that the strength was comparable to gravel and sand. The system is essentially the same.

          Papercrete is a little different in it’s composition from concrete. When you mix the paper with the cement you are essentially re-pulping the paper; grinding it back into fibers. These fibers swell as they absorb water. Like concrete, cement is added to bind the matrix of fiber together. Portland cement goes through a chemical reaction as it absorbs and binds to water. Papercrete also relies on this reaction but because the paper fibers have absorbed so much water it takes longer for the excess water to evaporate off. When it is fully dry the papercrete has the composition of a dense web or sponge with lots of little holes left behind from the paper fibers shrinking as they dried. Everything is coated with cement so the blocks aren’t as absorbent as a sponge but it still has sponge like qualities. This web of fibers are all intertangled and give the papercrete shear strength similar to the plastic shreds in the concrete block but at a much smaller scale. The air pockets in papercrete provide it with it’s relatively high insulating value. The minimal amount of mass required to the volume it fills makes for a substantially lighter product too.

          Adding plastic doesn’t increase the shear strength of the papercrete, probably brings down the overall insulating factor (a little) and adds to the overall weight( a little). I feel that when you add shredded plastic to papercrete you don’t gain much other than sequestering plastic that would otherwise go out into the waste stream. Which is a good thing but the plastic adds little to the properties of papercrete that makes it appealing. Adding more plastic further reduces the benefits of the papercrete. Finding a balance is the trick.

  6. walt
    Posted December 10, 2015 at 5:57 am | Permalink

    HI there folks. I’ve just recently found your papercrete adventure and am looking forward to looking at the other things I may find through instructables etc… Have you (or anyone that you know ever tried building a fireplace or barbeque-type structure out of papercrete blocks? I’m curious as to how well it would stand up to heat.

    thanks and have a great day!

    • Mike
      Posted December 10, 2015 at 9:05 am | Permalink

      The papercrete will burn. It doesn’t go up like a piece of wood but exposed to direct flame they will smolder and eventually burn. I tried burning one in my woodstove and it took a while but it did burn up. They would probably work as a secondary insulation around brick but you would need to experiment.

    • Jim
      Posted April 13, 2017 at 11:00 am | Permalink

      I would be very cautious when using this product near a fireplace / fire pit. I have seen concrete send pieces the size of your fist and larger flying over 20 feet. If there is any water left in the spaces of the papercrete, it can boil inside of the product building pressure until the structural strength is exceeded causing pieces to fly. I think I’d stick with fire bricks for my fireplace.

One Trackback

  1. By No More Trash « Stuff I Made This Year on February 20, 2012 at 4:30 pm

    […] slowly for a mile or so you end up with a bunch of pulped paper mixed with cement.  You can then cast this goop into blocks or any other form you like.  After the block has dried its light weight and very durable.  The […]

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