Frequently Asked Questions

All answers by Gordon Solberg, editor of Papercrete News, unless credited otherwise.

By far the most frequently-asked question is:

Q: What about building with papercrete and fidobe in wet climates?

This has been answered at length in the papercrete book, page 42. In brief, we should remember that papercrete and fidobe are ideally suited for dry climates, but there are people using it in wet climates. Paul Reavis used papercrete as infill between the logs in his cordwood barn built in Wisconsin in 1988, and it is holding up very well. We also have a report of a papercrete/cordwood house being built in New York state. The next issue of Papercrete News, out in May, will have an article about a papercrete/Earthship bed-and-breakfast being built on Vancouver Island, which is a very wet climate indeed.

Wet climate building strategies would include building on a stem wall to raise the papercrete at least a few inches off the ground, and including a moisture barrier to prevent potential wicking from the stemwall into the papercrete (which absorbs water readily). Build a roof with overhang, to keep as much water off the wall as possible. To get a waterproof, yet breathable exterior wall membrane, Leonard Jones (who wrote the article, "An Engineer Looks at Papercrete" in PCN #1) suggests using a stucco (type TBD) coating.

Build during the hottest, driest time of year. Papercrete/fidobe dry slowly and absorb water instantly, so always keep your work protected from the rain. Consider building a simple plastic greenhouse-type drying shed to hasten the drying of the blocks.

So my answer is: Yes, it can be done, if adequate precautions are taken.

Q: What about pumps?

A: A lot of people have tried pumping slurry, with varying degrees of success. We have been reluctant to give out much information about pumping slurry, until we could give the name and model number of a pump that really works, reliably. We finally have this information:

Tim Pye (who has a nice long article about his project in PCN #1) reports, "The pump I use is a 2" diameter diaphragm pump with a 5 hp gas engine, also known as a mud pump. The brand name is "Wacker" model #PD2B, circa 1991." He says it is working well for him, and needless to say, sure beats lugging buckets of slurry around!

More on pumps...

To pump the papercrete slurry use a concrete pump. Contact your local concrete batch plant for the nearest company. Some of the pumps may be costly because of the size and availability. A few companies may have a trailer type pump that is hauled around by a four wheel drive pick-up. I have used the trailer type to pump concrete for columns and beams for houses in south Florida. Doug Cline

I had a friend that was looking fairly seriously into building a Monolithic Dome and he and four other people we going to take the building class etc. The point to all of this is that they were going to go together cooperatively to buy the Targhee pump and that way the cost was distributed four ways. Maybe you would know of people who would want to cooperatively purchase a Targhee and cooperatively build? Beth Peterson

Hi! We just got the issue of Mother Earth News with your article in it that says that you are having trouble finding pumps that work. If that is still a problem, if you have not already done so, I highly recommend that you contact those in the ground-coupled heat pump industry. They are very used to pumping high solids grouts and grout mixtures, and are normally trying to get such mixtures to flow through a 1-1/2 to 2 inch diameter tremie.

I would specifically recommend contacting Dr. Charles Remund at South Dakota State University in Brookings who has recently done a great deal of work for EPRI and others on bentonite grouts and their emplacement. He is on the faculty in the Mechanical Engineering Department there.

Q: What about building in hot/humid subtropical climates, or building a papercrete sauna?

A: Four years ago, Mike McCain built a "snail house" (for raising escargot snails) near Alamosa, CO. The interior of the building is kept at 85 deg, at a humidity of 90%. To keep the humidity high, the owner keeps the papercrete floor soaked with a hose. The building is holding up well so far, which seems to indicate that papercrete would be feasible for hot/humid applications. In addition to the usual humid climate precautions, I would recommend doubling the amount of Portland cement (to 2 94-lb bags per 200-gallon batch). This won't prevent the papercrete from absorbing water, but will limit possible deterioration if it does.

Q: What about making sidewalks out of papercrete?

A: Not recommended. For some applications, such as foundations and sidewalks, where you need brute strength, concrete reigns supreme. Papercrete is much less dense than concrete, absorbs water easily, and is best used for walls and roofs, where insulation value is important.

Q: Can you build multi-level structures with papercrete?Where can I find plans to suit?

A: Yes, multi-level structures should be possible, if the first-story wall is thick enough (18-24") and you use enough rebar. But I know of no plans for such a structure.

Q: Has anyone tried to cast large sections, such as 20 feet long, 8 or 10 feet wide by 12 inches thick?

A: The biggest castings I know of were 4x8 feet, 6" thick, and contained 2 pieces of vertical rebar (8' long) and 3 lengths of horizontal rebar (4' long). They were poured flat on the ground. After they had dried (about a month) they were tilted vertically with a front-end loader. There are also walls being poured in place with slip forms; they typically have a thickness of 12". I am not sure what advantage there would be to casting 10x20 foot sections. They would be very heavy even when dry, and difficult to move without breaking unless they contained a lot of rebar. Slip forming the walls in place seems much more feasible.

Q: Where in BC is there a building underway?

A: Rick Price is building a hybrid earthship/papercrete bed-and-breakfast in Ladysmith, on Vancouver Island. His email is 3rdmill@nisa.net.

Q: I am looking for a light weight portable solution to covering my yurt. Would the papercrete stucco style possibly be suited for this? Also would it be suitable for wet climates?

A: I'm not sure how portable papercrete would be, unless you cast it in sections. But a 2" thickness would radically improve the comfort of your yurt. As for wet climates, papercrete should be sealed -- we have good luck with Homestar silicone sealer -- otherwise it will absorb water and will be very heavy, and not an effective insulator.

Q: I live in northwestern PA . How does papercrete hold up in cold wet weather? Specifically, snow for several months of the year. Will it stand up to snow shovels, etc.. I am interested in building sidewalks constructed with this material.

A: I would not recommend papercrete for sidewalks. Concrete holds up to abrasion much better, especially when wet. Papercrete is best for house walls, where it can be kept dry, and where its superior insulation value compared to concrete is beneficial.

Q: Has anyone considered building an underground house with papercrete or a papercrete/concrete hybrid? My intent would be to build this in the smoky mountains. I planned on building the walls out of surface bonded block and using a flat roof but, the flat concrete roof will have to be very thick (and Expensive). How about papercrete? I feel I would need some serious sealing on the material in this situation, What would you say? I am still a ways from building it but I want to get a definite plan before I start.

A: Papercrete would work OK for the roof, sealed with silicone sealer and/or elastomeric roof coating. I wouldn't recommend it for underground walls.

Q: We are planning to use papercrete for building raised garden beds. Ever heard of anyone using papercrete in this way? We poured our first blocks today and are still experimenting. I was wondering about the paperadobe. The soil on the school grounds is mostly clay. Wouldn't that work? Has anyone tried making a papercrete barn? Just think of the possibilities!!!!!

A: The trick to making raised beds out of papercrete, I think, would be to use a high cement content. For a 200-gallon batch, that would be a full bag (94#) of cement to about 60# of paper. Even more cement might be better.

Experiment and see what lasts best. I do know that plant roots will grow into papercrete made with half a bag of cement per batch, if the blocks stay damp. Dirt with a high clay content would work great for fidobe. I know of a papercrete/cordwood barn in Wisconsin.

Q: Where do you get so much paper? Can it be mixed with and concrete electric mixer? Intersting.

A: Getting paper is no problem! Newspaper publishers usually have bundles of unsold copies they will give you. A cement mixer works if you shred the paper first.

Q: What about packing tires with papercrete?

A: It would work, but the slurry would shrink somewhat as it dries. You wouldn't get the tires to bulge like when you pound in dirt with a sledgehammer.

Q: Hi, I live in Oklahoma, where it is frequently quite windy. How does this type of structure hold up to high winds? Possibly even small tornadoes?

A: It would be important to anchor the structure to the foundation with rebar, steel strapping, etc. If the structure is properly anchored, high winds shouldn't be a problem. With tornadoes, all bets are off!

Q: How this material has fared in northerly climates, and if it will withstand the rigours of a Canadian winter.

A: The truth is, no one knows yet. There is a hybrid earthship/papercrete structure being built on Vancouver Island, a very wet climate. A cordwood/papercrete barn in Wisconsin is holding up well after 12 years. I think once a properly-designed structure is built and properly sealed, it would do OK. But the problem would be getting it built in the first place, in a climate with a shortage of warm/hot dry weather so the slurry would dry.