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A papercrete wall?

 
Jeremy Droplet
Posts: 25
Location: Central Maine (Zone 4b)
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As I'm getting closer to finalizing my land purchase, my designs are coming closer to fruition. I'd like to do my best to utilize the resources available on the final chosen site. I'm in a wooded area, but good timber is scarce as most of the land has been previously clear cut. Only some saplings and old trees remain. A majority of the good poles have been cut. The site does have a fair bit of clay and gravel is close by. This makes earth building possible. I really like the idea of earthbag/superadobe walls, but this style of building is labor intense. It will probably be used for the main house down the line. However, this post is more about my first structure; something quick and cheap yet still structurally and ecologically sound. I've only got a short time before winter closes in, so speed, cost, and ease of construction are important.

I've read Oehler's book and have been a fan of underground/earth bermed construction since. However, even with reclaimed barn boards as my shoring material and reclaimed posts, the cost to build this type of wall system would be too high. Enter papercrete... Huh? Papercrete for earth bermed walls you say? It just won't work!!! Or will it. Hear me out.

Rather than the standard post in ground, I'm thinking rammed gravel/tire post foundations set about 3' below grade, capped with concrete, and fitted with 'mostly' green timber poles harvested from the property.

Think this - https://www.youtube.com/watch?v=mUtTwalmN2U

I don't have easy access to a cheap and sustainable material to use for the shoring. Instead of rough lumber, I plan to run chicken wire/stucco mesh taught between the poles. The mesh will have waste cotton fabric or burlap stitched on. Onto this surface, I will spray an appropriate papercrete mix with a mortar sprayer.

Mortar sprayer - https://www.youtube.com/watch?v=twt1srsq_Hg

It will take quite a few coats, but with a high output sprayer like this, I think a wall could be done in a day or two.

The next step is the poly sheeting for a vapor barrier. Rather than polyethylene, I'm leaning toward EPDM as a waterproof membrane. Then of course comes a good draining earth backfill.


What else am I missing? Why wouldn't this work? I know the papercrete will want to wick moisture. I think finding some way to run a vapor barrier under the wall makes sense. I can run a gravel/rubble trench in between the tire piers to help this. I also know cellulose materials tend to attract insects. I don't necessarily know that will be the case here though. And if untreated wood as shoring doesn't invite these pests, I can't imagine papercrete will.



I'd love any thoughts or input on this before I run out and start buying tools!

 
R Scott
Posts: 3305
Location: Kansas Zone 6a
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Maybe in the desert, but in Maine

Standard Ferrocement will use less cement than papercrete for the strength you need (but more metal and no insulation).

Or maybe you could do a rapidobe: http://velacreations.com/shelter/building-components/walls/rapidobe-walls.html

Ground contact in wet areas is problematic at best. Even concrete fails quickly if you don't have absolute control of the water.
 
Jeremy Droplet
Posts: 25
Location: Central Maine (Zone 4b)
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Of course moisture is the primary concern, hence the emphasis on good drainage and keeping moisture out of the wall. I would recon that an appropriately designed roof, good draining backfill, and a solid vapor barrier will keep the majority of rain water away. My bigger concern is moisture being wicked up through the wall. Here is where I'm thinking it makes sense to devise a vapor barrier system that carries continuously under the wall. Or maybe a rubble trench with french drain is enough to send moisture away.
 
R Scott
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It isn't JUST the groundwater that is a concern, it is the overall humidity. You may have less of a problem because of the cold; you have more "heating days" per year and if you heat with wood it will help to dry out the walls. And adding borax and lime can help prevent mold. But I still wouldn't do it below grade. Even if you can seal out the groundwater, you have sealed in that side of the papercrete so it can't breathe.

 
Jeremy Droplet
Posts: 25
Location: Central Maine (Zone 4b)
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R Scott wrote:It isn't JUST the groundwater that is a concern, it is the overall humidity. You may have less of a problem because of the cold; you have more "heating days" per year and if you heat with wood it will help to dry out the walls. And adding borax and lime can help prevent mold. But I still wouldn't do it below grade. Even if you can seal out the groundwater, you have sealed in that side of the papercrete so it can't breathe.



I'm under the impression "breathability" is the key to keeping any cellulose-based wall healthy and happy. I've read dozens of books on strawbale that highlight the moisture concerns and the appropriate solutions (namely keeping water out, but keeping things breathable). I know for a fact I want and EPDM layer or something to that effect bordering the exterior wall. I will stick with a breathable plaster material for the inside finish similar to earthships.

I don't foresee the structure being dark, dank or murky. With big south facing glazing and good airflow I don't think inside humidity should be anything above average. We do get a fair bit of rain. 39" annual precipitation or something to that effect. But the rains will be captured from the roof and otherwise intelligently sloped away from the homesite. Rubble trenches with french drain pipes sloping down grade will likely be used to provide a foundation.
 
Len Ovens
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Jeremy Drolet wrote:

I don't have easy access to a cheap and sustainable material to use for the shoring. Instead of rough lumber, I plan to run chicken wire/stucco mesh taught between the poles. The mesh will have waste cotton fabric or burlap stitched on. Onto this surface, I will spray an appropriate papercrete mix with a mortar sprayer.



Assuming you feel comfortable with the other aspects of things, I would suggest one change to your procedure. Wood shoring dictates straight walls which also make the best use of woods strength. Paper/whatever-crete would do better curved out. Maybe behind the chicken wire (which I would leave loose) put an air filled balloon of vaporbarrier. I mean two sheets with an air hole and a pump to keep it pillow shaped till the first layer dries. Then add your other layers. It should be much stronger. Maybe the chicken wire would be strong enough to hold a curved shape with out the balloon too in which case it could be a single plane curve instead of sphere. Making your building dome or vault shaped in general is better suited to the material. The form of the wofati is because of the building materials. The shape and design of a *crete bulding should also be because of the material.

An inverted dome of concrete "because it looks nice" would not be ideal...
 
I agree. Here's the link: http://stoves2.com
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