Papercrete as Plaster
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Q: Seems like papercrete would be a good plastering material for the straw bale house I am building. It breathes well which is important for the bales. Do you think it would adhere well to the bales?

A: I know of several situations where papercrete has been used as a plaster over straw bales, and it has worked out well. The papercrete should adhere to the bales just fine, especially if it is the straw ends that are exposed and being plastered.

Q: Perhaps it should be sealed somewhat so moisture does not reach the bales? If so, maybe use a limewash which I understand still breathes?

A: This might be a good combination. I used a lime plaster over papercrete on the inside of my house, and it adheres pretty well, especially if the papercrete is textured roughly. I suggest some controlled experiments to see what works.

Q: Chrysalis Living Center here in Tucson builds houses which are "stuccoed" with papercrete. It is shot on under pressure from a hose just like conventional stucco. In this case, it is covering polystyrene sheets lathed with stucco netting. I am wondering why I couldn't just shoot the papercrete onto the strawbale walls in this way?? Do you think it would adhere well doing it this way?

A: I'm pretty sure the papercrete would adhere just fine to a rough straw bale, especially if the bales are oriented with the straw ends sticking out. Spraying the papercrete would probably be a very effective way to do it, if you have access to the equipment to do this.

C: I sure wouldn't want to have to put stucco netting on my bales though (groan). I was already thinking of making a water storage tank/pond by shooting papercrete on the sides of a huge hole which has been dug on my property (to get enough earth to build up the floor between my (way too big) stem wall ordered by the county for the strawbale house.) I would then line it with visquene I guess. Point is I would have the machine already on hand to use for perhaps shooting the straw bale.

A: You would definitely need to line the tank with plastic, or somehow waterproof it, or the papercrete would wick the water to the other side.

Q: I am wondering if the lime could be used right in with the papercrete mix -- much as they do with a lime stabilization for earthen plaster? Has anyone ever done this?

A: I recently read a book by Charmaine Taylor called "All About Papercrete", where she describes lots of experiments with different formulas, including the use of lime. As I recall this can work, especially if there is also some clay in there to help harden the lime. The curing time can be very long, and the resultant product is not likely to be as durable as papercrete with Portland cement, especially in situations where it might get wet.

Q: What machinery do you use to spray the papercrete?

A: I did not use a sprayer on my house. All of the papercrete was applied by hand. I did try an experiment with a sprayer once and it was a partial successful, but it required a huge compressor and was difficult to control. I do know that papercrete has been successfully sprayed using a diaphragm pump with considerable air pressure. The paper fiber has a tendency to clog nozzles and small diaphragms.

C: I read about using paper, water, and cement as a plaster. I don't know how it will withstand our termites so I will have to give it a try.

R: As you may know, we used "papercrete" to plaster both sides of our earthbag domes, and it has worked out very well. This material does seem to resist termites and other insects.

C: As it is working against gravity, I am stumped as to what to use and how to keep it from falling off.

R: We had the same situation with our domes, and I used polypropylene baling twine wrapped around the earthbags as I built the structure (circling 3 bags at a time) to give the interior plaster something positive to grab onto. Also I used a very light mix of pure papercrete (no sand added) on the initial coat. This I threw up on the wall by hand and let it splat and dry in place with a very rough texture. It is amazing that the stuff would actually adhere to horizontal surfaces and dry in place. Once it has dried, more can be added to fill in all of the voids and make as smooth a wall as desired.

C: You discovered that throwing the crete helped it stick better than troweling. This has been done with pure lime plasters for hundreds of years and is called "Harling"..there is even a type of exterior lime plaster called Lime Harling...a thin flexible tipped wide trowel is used to scoop the plaster, then flung with force against the surface, it is lightly trowelled then and left to cure. The Scots are clever folk and found they could be more successful with plasters in a harsh climate if they flung it ( hence the Scottish fling- but that's another story) there is an engineering principle behind this, ( don't ask me to explain it) and I have also written about it when building my cob-crete garden bench. I harled the cob/crete plaster or threw it by the handful. and it is a wonderful tension releaser...! (Charmaine Taylor)

Q: And do you know at which point there is no breathing in a papercrete wall? Or is every papercrete wall breathing well?

A: I believe that any papercrete wall will breath, as long as it is not painted or coated in some way to prevent that.

Q: Will papercrete adhere to expanded polystyrene? I know the synthetic stuccos like Dryvit will stick to foam board. It would be really nice if it will stick to the foam board???

A: I've never tried what you suggest, using papercrete to cover foam board, but I have my doubts that it would stick. Papercrete does best as a stucco when it has a fairly rough surface to adhere to, otherwise it just doesn't tend to stick that well.

Q: How is the external papercrete on your house holding up?

A: I'm quite pleased with how the papercrete is holding up so far. One building is already about five years old and is showing no sign of deterioration. There are a few small cracks in the papercrete plaster in some places, especially on the south side that experiences more thermal stress. However, since I imbedded chicken wire in the final coat, and since the entire earthbag structure is not vulnerable to moisture damage, these cracks do not concern me. I will eventually caulk them to keep the material from flaking off.

Q: I am interested in using papercrete as the stucco/wall material in a Tudor style cottage home in New Hampshire where there is a lot of snow! The material would not be used in a load bearing application. The material would be exposed to a lot of weather. I am looking to make it waterproof and fireproof. Is the GeoCement product a way to go in lieu of regular portland cement as it is waterproof and fireproof? Any idea if it is financially realistic?

A: The main thing to realize with papercrete is how much is likes to absorb moisture when it has a chance. It is like a sponge. So it is best used in situations where, even if it gets wet, it won't cause any harm. If it is allowed to breath it will evaporate any moisture quite readily, but if it is sealed and still gets wet, then it will stay wet and could cause problems. I have not actually tried the Geo Cement product, so I don't have direct experience with how well it works or how cost effective it might be. It does seem like a reasonable approach to waterproofing and fire proofing papercrete, when necessary.

Q: I recently purchased land and am living in a single-wide trailer until I can build. Any ideas on a cheap fix for poor insulation? Could I papercrete the outside walls?

A: A fast, but temporary, approach to insulating a trailer is to line the exterior walls with straw bales where possible. This could last a few years. Papercreting the exterior could be another solution, but it would take a lot longer, and the whole question of dealing with moisture might be an issue. Papercrete holds water like a sponge.

C: I bought a new manufactured home in 1992. I was having problems with plaster sticking to pillars that were not plastered right. I took the papercrete idea and used it. I soaked newspaper in hot water, then ran them through a blender, and added the cement. I used this instead of the plaster and it worked great for the repairs. No more problems. Since then, I have used a regular paper mache mixture of paper, flour and water to add a textured plaster finish over a very ugly wall. (P.S. Don't forget to add a little wintergreen to keep the mix from spoiling before it dries!) After this dried, I painted it and have a great looking wall with very little money involved.

Q: Could cob and papercrete be combined?

A: I did an experiment at the last Natural Building Colloquium of applying a papercrete plaster over an existing cob wall, and it seemed to adhere quite nicely, although I have not returned since to see how well it is doing.

Q: I have to make a small walls inside the house to divide the bed rooms and the living room. I want to use papercrete to joint the bricks and finally as a plaster. What do you think about this? Is it possible or not?

A: This seems like a good idea to me...I don't see why it wouldn't work. You can trowel the papercrete as smooth as you want. Many of my interior walls were done this way, and then stained with a wash of latex paint mixed with a lot of water.

Q: I was wondering about using a papercrete first coat and then a finish coat of ferro cement on my home. I live in Arizona where it rains only in the monsoon season and I live in a questionable flood zone so my house is two feet above the surrounding ground.

A: I think that idea is a good one; the initial coat of papercrete would provide insulation, while the final coat of ferro-cement would provide durability and fire protection.

Q: Is using cement in covering papercrete buildings a good isolation material to increase the poor moisture resistance of the papercrete blocks or not?

A: A plaster of cement (stucco) would definitely increase the resistance to moisture entering, especially if it has a high ratio of cement to sand.

C: I was raised with an Uncle who was a stone mason/landscape architect in California. I still love mixing mud or cement (now papercrete and earth plasters by hand). I want to share with you two of my latest finds. One using a pudding thick wheat paste mixed with very fine nature colored sand or clay to make an earth plaster faux brick archway that folks can't believe ain't real.

Second is using the new 85% recycled paper blow in insulation in my paper crete mix, allowing for less water and special mixing. I use 1 part portland cement, 1 part fine sand and/or clay, 1 part blow in insulation and I use a portion of masonry white glue in the mix too. I am using that as an indoor outdoor earth plaster and hope to pour my faux adobe courtyard walls using that mix as well.