Step 4: Making Papercrete Blocks

Making blocks is super easy.  After mixing up a batch you just cast it into forms.  

Papercrete mixer

Block molds- mine are made from 2x6's and scrap siding

Bathroom scale- for measuring out the paper



Paper (used of course)

Shredded plastic (if you want)

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


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 in front of the molds.

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

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

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

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.

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.

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 you've got some shoveling to do.  The type of material you are using can make a difference too. Cardboard makes for a thicker, chunkier mix where newspaper is finer and smoother. Sometimes I use a plunger to force it through too.  A lot of poop jokes get made here. Let your imagination run wild. I get about 45 blocks per batch.

8.  Remove the molds.  I do this right away.  I want as much air flow around the blocks as possible to help them dry.

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

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. 

Once you have a big stack of blocks It's time to build something.  I've been putting up little buildings all around our place.  Let's take a look at a yurt I built out of papercrete blocks.
I read in cellulose fill howto that adding borate will make not only fireproof your paper/cardboard mix, but also mildew and rodent proof it! Now I found that the major ingredient in Borax is sodium borate?! Is there any way, by adding borax to your mix, make the papercrate even better?!
It is entirely possible that adding borax would be a benefit. I haven't seen any studies that methodically tested it. I know that in my experience I haven't had any issues with insects. I've tried burning papercrete blocks and it takes quite a bit to get and keep them going because they are relatively dense compared to paper. For me, the cost of an additive outweighs the benefits. I would be interested to know if anyone had tried adding borax and done side by side testing.
I had planned to build a test tiny house out of pallets and use a form of papercrete as insulation ( inbetween pallet top & bottem) wasnt considering using concrete thou.. just cellulose "panels".. but the 'crete might the ingrediant I need.. maybe half the crte in favor of the borax and press out the remaining water? Hmmm this will take some thinking..
I'm obsessed with your instructibles and your website these past few months! I have space constraints in my yard, so a tow mixer isn't practical. My dad and I are discussing a stationary mixer powered by a giant, powerful, industrial drill he already has (he's a heavy machinery mechanic and welder). I'll share if this idea pans out. Meanwhile, I'm experimenting with smaller batches using cross-cut, pre-shredded paper and a bucket. I've started testing recipes by hand-sculpting big faux rocks for my garden. I wanted big, natural stones, but I can't manage the weight of real rocks by myself, and the cost of the lovely stones I liked would have allowed me to buy maybe one, haha. Now I can make as many as I want. For bigger rocks, I hide nonrecyclable trash (mostly styrofoam packing material) in the middle, inspired by the really cool "trash rocks" ible. I paint them using flat-finish paints in natural colors. So far, they look great and are easy for me to move around and rearrange to my heart's content. We'll see how they hold up, but I plan to try to use my fake rock technique to build a small "stone" privacy wall to hide my trash cans. Then maybe a garden shed...and then maybe.... Thank you for all the inspiration!
I think there is a lot of potential in casting papercrete into all sorts of shapes. I'm looking forwards to seeing some pictures of your rocks. The one thing I would say is to make some sort of foundation for the &quot;rock&quot; wall. While there is no need from a weight perspective, it is important to have a barrier between the PC and the earth. I've found that the blocks I used to make raised beds with are slowly decomposing from their exposure to moisture. You might try metal flashing underneath the wall. <br>Good luck on your projects!
<p>This looks like it would be a excellent material to build this https://www.youtube.com/watch?v=02NtjypMHwk</p>
Quick question. It may have been ask already, but what do you do to water seal papercretw? You mentioned it can not be buried because it will break down. You also said it soaks water like a sponge. What do you do for out door use. Can you use thompsons water seal or some other concrete water sealer. <br><br>Thanks <br>Allan
<p>I am working on a building material that is far more versatile and costs from. &pound;0.00. Yes thats right you can get the material for nothing. Some places charge I am going to use it for pre casting wall/door/window panels. Anyone interested email:</p><p>garyjmcneish@gmail.com</p>
<p>I first found out about papercrete while searching for an alternative to hypertufa (I'm visually impaired and didn't fancy the chance of inhaling any of the fine cement dust because I'd need to be close), but your Instructable really explains it, thank you. Not that I want to make a house! I've been wanting to do craft casting, small items, and this encourages me to have a go.</p>
Brilliant, but I think the amount of rain we get in the UK would make it impractical.
<p>not really just use a water based breathable spray on coating. </p>
Here in western Washington state we get lots and lots of rain. The best siding material for our houses is Hardi-Plank, which is a paper fiber/Portland cement composite. It's all a matter of how good a job you do of shredding the paper and mixing its fibers into the cement matrix. Done properly, the stuff will last for a geoduck's lifetime.
I live where wind chills of -40&deg;F are normal. Some years we have 10 or more feet of snow. I have two questions. 1 - if filled full of dirt to begin with will raised garden beds withstand that kind of weight? 2 - I will only be able to make a few pieces at a time. How warm does the outside temps have to be for these things to cure?
<p>abut the same 4 a normal concrete block.</p>
I tie the back of the papercrete blocks together with a strip of galvanized steel which is screwed to the blocks. This helps keep the dirt from pushing the blocks over. As far as snow I think that all the snow around the bed would provide some sort of support. I've had three feet of snow with no I'll effects. <br><br>As far as temp. I'm in New Mexico where it is quite warm and dry in the Summer. I usually cast blocks in June-August with temps in the 80's - 90's. The blocks dry in a week or so. They will cure at any temp above freezing but may take a long time to fully dry. One thing to do is make blocks one season and stack them to dry with some sort of cover and come back the next year to build with them. I've done that with larger projects where it takes a while to get enough bricks to build a building.
<p>I am using a different size tank for my mixer. Can you give me an estimated amount of water you use? Also, can I add wood shavings from a planer to the mix?</p><p>Thanks in advance!</p><p>Dave</p>
<p>I'm using about 150 gallons of water to one bag of cement to 75 lbs paper. I think it would be perfectly fine to add wood shavings though you may need to add more water if the mix is too thick. Don't skimp on the paper since that's what's holding it all together. A little experimenting will dial in the perfect mix.</p>
<p>Thanks a million Spike! I will post photos when I finish my mixer and any tech notes I may come up with.</p>
<p>Awesome! Looking forward to it. </p>
I really enjoyed your project. I found it first on Mother Earth, then came here via a link. The only thing I would criticize is calling this a yurt. Just because it is a round dwelling with a self supporting roof does not a yurt make. The true definition of a yurt is a completely modular dwelling that can be taken down and reassembled. You could rename it a yurt-like building, but this is like calling an A-Frame house a giant pup tent! <br>The mixer thing is brilliant. I plan to move to Austin soon (I am currently in Hawaii) and will be purchasing some lake land property and am looking at all kinds of simple yet structurally sound building ideas. Yours is definitely at the top of the list!
Spike, I apologize if you covered it somewhere but I couldn't find it - did you mortar between the blocks? It looks like you did... what did you use? If it is traditional cement mortar, how well does it bond to the blocks, especially over time? Some of the comments about the papercrete absorbing moisture and expanding/contracting similar to what wood does as humidity levels vary makes me think that traditional mortar would eventually separate from the papercrete.
I used papercrete to mortar the blocks together. You can also use it as a plaster as well. It adheres really well to the blocks. Cement mortar doesn't stick well at all.
Do you need to spray poly or something else over this after it dries to make it more waterproof or does it not swell at all when it gets wet, or will poly or other product hold moisture in and make it deteriorate faster? How about anchoring it to the foundation, is it necessary, and if so, what would be the best method- threaded rods through the wall down to the foundation? How deep and wide does the foundation need to be, 6 inches wider than the blocks and a foot or more thick? This looks like a really good product you are making, I just want to know more about it so I can build stuff with it and know how well it will withstand the elements in central North Carolina- high humidity all year long, some snow in winter and 100 degree days in the summer. Sometimes it will rain for days in the winter as well. Any input there for me?
Putting an outer coating on the papercrete is probably a good idea for where you live. There are bunch of ideas/suggestions in the comments. I'm opting for large overhangs on the roof and maybe stucco someday. My foundation is only 1' wide and 6&quot; deep w/ two rings of rebar inside. I didn't tie the building the foundation but threaded rod or J hooks would be the way I would go. If it were me I would make a small shed or other starter building first to see how it holds up in the NC climate before I invested a bunch of time in a major building project.
One of the best - I love this instructable <br>can you actually give the proportions the way it is mentioned in cement mortar <br>like 1:2; 1:4 etc?
I get 13:1:0.75 water,cement,paper by weight. Your results may vary but it's a starting point.
i am prototyping natural fiber reinforced garden and patio-ware in limecrete. burlap, weldbond, perlite, portland, builders lime, foam and hemp hurd are in the mix. papercrete and hempcrete are not recommended to be in direct contact contact with earth yet you are making raised beds and planters..for precast pots and such my mix needs to be pourable so i treat the burlap and hemp hurd with acrylic cement binder, (weldbond) . this makes the fibers not soak up water and the mix retains good workability. your planters show some breakdown on soil side after three years... in desert climate. i have no idea how long my pots will last, but 3 years seems a bit short for commercial product...any thoughts?
I have the biggest breakdown issues where the PC is buried underground. Treating the earth facing side I imagine will address most breakdown issues for a planter. Really you would just have to test it to see. PC is great as a castable material. It molds really nicely.
The best part about this article is the mixer. Genius.
I love you, thank you
Papercrete similar to timbercrete IS a brilliant building material. Having worked at timbercrete for 2 years and personally comparing different materials against it..... i would never build with anything else.
Sorry, but that papercrete just does not seem to be an efficient building material, nor does it seem to be a good choice. <br> <br>First, something made without any quality control cannot be expected to be consistent. I looked at other websites about the material and saw nothing about compressive strength. <br> <br>Anything that absorbs and releases moisture also changes size, creating cracking and settlement issues. <br> <br>The combination of cellulose, water, and warmth is an incubator for mold and vermin. <br> <br>Earth based blocks, such as abobe and cobe, even thought some contain straw and other organics, are a much better solution, and are by far greener. Look up what is required to make cement.
'' Earth based blocks, such as abobe and cobe, even thought some contain straw and other organics, are a much better solution, and are by far greener. Look up what is required to make cement. '' <br>With a lot of such structures that I seen, they still use cement to get the extra strength and to avoid the structure to crumble with the present of moister and water. <br> <br>Red bricks, gray cement blocks, wood, drywall and plaster and many more can and will absorb water and moister and they are used in everyday building constructions. <br> <br>If someone wants to moister and / or water prove such materials, all they have to do is paint it with the right paint for the application or use other protective materials such as a vinyl siding for example. <br> <br>
Ahh....a wealth of opinions makes the world a much more interesting place.
Well, actually Spike, THANK YOU!! GREAT stuff here. I live between Maui and Southern Oregon and have wanted to build some simple out buildings on both properties for some time now. Though CMU is DEF a possibility, I LOVE the similarities and flexibility with the Papercrete approach because I'm NOT limited to the dimensions (AND cost) of traditional CMU's. Though you mention the R-values of PaperCrete Units (PCU's), let me ask: How are the thermal qualities in WARM weather. I'm pretty much assuming they are similar in the 'reverse', keeping the interior cooler when it's hot outside ~ ~ ~ <br> <br>Also, can you provide a more specific 'recipe', ie, %concrete to %paper to %plastic. You mentioned about 75lbs of paper to 95lbs of cement, which is about 45% paper and 55% cement. I guess I'm asking this: What would you consider to be the upper range of % of paper content? Could the ratio be 50/50 by chance. Here's another assumption I'm making: The 'paper' one adds to the mixture could be pre-shredded if one were to acquire a source of that nature. Since you mention you get 45 blocks with a dimension of 8&Prime; x 12&Prime; x 5&Prime; per block per 'hopper', with a mortar bed that's roughly 2 blocks per square foot and 22 square feet per hopper. NICE!!! <br> <br>To address a comment about 'bottles' and 'stack wood': IF you were to incorporate these 2 different design features into a Papercrete building you would need to assure that the 'joint' between the 2 different building types adequately addresses the load differentials that would be an inherent part of the structure. For bottles, it would be BEST if you build a lintel 'header' over the are you anticipate installing a bottle section. Glass bottles are NOT inherently strong NOR are they 'structural' IN ANY WAY. They are WAY too brittle, and just imagine what a PIA (Pain in the A**) it would be to replace one that broke from a poorly planned installation. If you build a lintel over the area where you intend to install a bottle section, that lintel will carry the weight of the Papercrete blocks above and therefore (HOPEFULLY) prevent pressure cracks/breakage on your bottle section. <br> <br>With 'stack wood', there is another set of issues related to a combined style of building in that 'stack wood', unless TOTALLY dry with optimum moisture content (roughly 3%) and dimensionally stable, will shrink, warp, crack, and check. It is IMPERATIVE that you structurally segregate (expansion joint material) the stack wood from the Papercrete so that any of the wood's dimensional instability can be isolated from the rest of the Papercrete blocks OTHERWISE you'll lose structural integrity in the Papercrete blocks as well as the stacked wood ~ ~ ~
what is the mixing ratio for smaller batches than a stocktank full?
Scroll through the comments. It's covered a couple times.
One small suggestion: 'Cement', at least the 'Portland' kind, is composed of the following materials: <br> <br> Lime or calcium oxide, CaO: from limestone, chalk, shells, shale or calcareous rock <br> Silica, SiO2: from sand, old bottles, clay or argillaceous rock <br> Alumina, Al2O3: from bauxite, recycled aluminum, clay <br> Iron, Fe2O3: from from clay, iron ore, scrap iron and fly ash <br> Gypsum, CaSO4.2H20: found together with limestone <br> <br>When it comes into contact with water it begins to form a crystalline structure which gives it its inherent 'hardness' and building qualities. Spike mentions he removes the molds for the bricks IMMEDIATELY allowing more 'air to circulate' for, I assume, the quicker availability for the bricks to be used in the project. <br> <br>BIG PROBLEM HERE: Quickly drying cement does NOT allow for adequate crystal formation in the cement therefore a weaker brick SOMETIMES not curing at all which subsequently will cause it to crumble. <br> <br>SUGGESTION: AFTER stripping the molds from the bricks, cover the bricks with gunny sacks OR ANYTHING that can hold moisture, ie, rags, towels, sheets, etc. There's even a product you can buy just for this purpose, but since economy is a driving factor here, the cloth-type coverings work just fine. The trick here is to NOT LET the CLOTH dry out, EVER! Afterwhich, over the next few days, better if it's weeks, maintain the moisture on the gunny sacks which will allow the crystalline structures to form which will result in a brick harder and stronger than the Hinges of Hades and MORE moisture resistant to boot. IF POSSIBLE, allow the bricks to 'cure' for a month and you'll find your bricks harder and stronger than even Thor could destroy. <br> <br>I once did a concrete job in La Costa/Carlsbad California where we were able to actually bury a house slab UNDER WATER for 30 days. When we uncovered the slab and had to make saw-cuts for some revised plumbing, our Demolition Contractor said he'd NEVER seen concrete that hard and had to blow through more diamond bladed saws than he originally bid the project for. We were glad to compensate him for the additional costs because he did a GREAT job ~ ~ ~ The slab didn't even crack and the FIRST RULE of CONCRETE work is: &quot;Concrete is GUARANTEED to crack! EVERY TIME&quot; ~ ~ ~
Great comment thanks!<br>Lots of good info.
shades of THE MOTHR EARTH NEWS!!! Why not collect empty bottles, and use the stacked cord wood method, only using bottles? <br> <br>In MEN, they showed how to build using cord wood in a structure as &quot;blocks&quot; , the entire structure is stucco'd on the outside and made waterproof with polymers (or waterproof stucco cement. Keep open ends inside the structure so as not to trap water, You could leave a section or two more exposed inside and outside to allow a skylight effect. <br> <br>None of this is my idea look around on the net and go to MEN to view and buy old issues. (http://www.motherearth{ take this out }news.com/ <br> <br>A thought on caustic and paper. If the paper all decayed and there is enough cement, would you then have a nice porous sponge, that is strong?
A bunch or stuff: <br> <br>1. i want to make one, as far as compressive strength, i'll drive in coated rebars and tie them to the roof <br>2. you mention the papercrete absorbs water, could you coat the outside w/ cement? <br>3. very nice ible- very informative <br>4. you said it has been a year now, with no problems, good enough for me. <br>5, i'd put in few round holes for windows, <br>5.5 one could totaly live in this 'yurt' <br>6. @ how long did this project, just building part. <br>7. thanks very much for posting <br> <br> <br>
There are a bunch of waterproofing options discussed in the comments. <br>Windows would be a nice touch. Mine has a big skylight which adds a nice amount of ambient light to the space. I can't really give a good estimate on the amount of building time since I did it in fits and starts mostly by myself. I would say one motivated person could easily have a habitable structure in one building season. <br>Good luck w/ your project. Post pics!!
I wonder if it would be possible to work out the form and cast complete geodesic dome triangles? Cast the sections with a taper so they just fit together without the usual brackets.
http://starship-enterprises.net/Paperdome/ <br>
Nice job... thanks
It seems that a big problem with the early experiments using cellulose based mixes (including stuff like Excelsior shredded wood) was that the alkali cement would degrade the fibers over time. Any concerns or direct experience with this?
That's why the more recent fiber reinforced cement products use alkali resistant fiberglass strands.
Lovin' your idea! We just got finished with a pallet shed with an outside bar and storage on the other side. Think this may be in the works for the next &quot;storage&quot; area!
Careful! If you're like me you'll fill your papercrete shed with paper for the next shed and so on and so on. It's a slippery slope. ;)
That's funny! Luckily we got to fill our pallet shed with all our woodworking tools.

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Bio: I have a compulsion to make stuff, all kinds of stuff. I'm glad to be here...
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