FAQ - Frequently Asked Questions

 Can I build with Papercrete in a wet climate? I am often asked this question. Since Papercrete is mostly wood fibers, it needs the same protection from moisture that wood requires. Papercrete will not soften when wet, but it will begin to get moldy. So it must be kept dry. One person suggested adding lime (high pH) to the mix to make it too alkaline for mold to live. I have not tried this, but it might work. Also, Papercrete can be painted, just like wood.

Can I use Papercrete in place of concrete?
Since Papercrete looks similar to concrete and is often used instead of it, let's compare them. Papercrete is far lighter in weight and has remarkable insulating qualities, unlike concrete, which is relatively heavy and often feels cold to the touch. Although Papercrete does not have the compressive strength of concrete, unless one is building something that requires the hardness of stone, like a five-story building, the hardness of Papercrete is often sufficient. You can hold a gas torch to Papercrete and it will not ignite or burn, so a house made from it is safer than one made from wood. It is easy to shape when cured and dry. It can be cut with an ordinary wood saw, carved and drilled. Try that with concrete.

Footings, floor slabs and such are best made from concrete, as they usually must have great compressive strength and are often exposed to moisture. However, Papercrete can be used as a floor material, if it will not have to endure heavy traffic, and if it is insulated from the moisture of the earth below. Papercrete can bear some loads, as in walls supporting a roof, but for heavy roofs, it would be better to use more traditional structural supports - wood, metal or concrete columns - to support the roof, and use Papercrete for the walls.

Fibrous adobe is another story, because it does have compressive strength. Walls made from it will support much more weight than will Papercrete. It is also more similar to concrete in having thermal mass, depending on the proportion of paper pulp to adobe.

Is there an exact recipe for Papercrete?
No, there isn't, and that is the reason for the wide variation in properties from one batch to another. It is possible to make Papercrete and fibrous adobe using exact proportions. I suggest doing experiments with various amounts of paper to cement or adobe to find the properties you need for a specific application.

If you want insulation, use a lot of paper and less cement. If you want mortar or plaster, use more cement (more than a pound of cement to a pound of paper). If you need compressive strength, add sand (but not gravel). Experiment with a food processor on small batches, cast a block or whatever, wrap it in plastic and let it cure, then dry it completely. Now test your sample to see how it behaves under conditions similar to what you require.

Be sure to note down the amounts of each ingredient so you can reproduce the recipe on a larger scale, if you find one that works for you. Weight is more accurate than volume for paper, cement, dirt, lime, sand, etc., but volume is fine for water.

Can I use fibers other than paper?
Of course! One man wrote me from a tropical country that he was using bamboo leaves - they have strong fibers. If you have a good food processor, I suggest going out and collecting weeds and grasses that are abundant in the area where you are building, and then do experiments with them to see if any of them perform well in place of paper. Recycling old paper is great, but why not recycle the weeds on your land? Some weeds have strong, usable fibers that may work better than paper, which has rather short fibers. Sawdust and wood shavings, cattails, straw and other grasses, horehound and other weeds - all of them have fibers and might produce good building materials, combined with either cement or adobe or a mix of dirt and cement (stabilized adobe).