Porous lava rock — scoria (cinders) and pumice — is an ideal building material. We’ve covered this amazing material many times on our blog, but I just learned something very exciting. It turns out scoria is available in Alaska, British Columbia and to some extent the Yukon. All these areas have cinder cones (a type of volcano) that produce scoria. This is great news because porous lightweight lava rock is a good insulator and also fireproof, rot proof, easy to work with and doesn’t attract pests. It’s affordable if there’s a nearby source to minimize shipping costs. So this discovery makes it practical to build lightweight superinsulated earthbag houses in Alaska and Canada. Use the search engine on the right to search this site for details and example projects.
Many people have asked me about how to build insulated buildings in Canada and Alaska and so far I always thought scoria was not available. No one ever looked. For instance, we’ve discussed this at length concerning my free Solar Pit House plan that’s designed for cold climates. Here are the free drawings. Search this blog for previous blog posts about scoria and the Solar Pit House.
Definition of cinders from Volcano Explorer:
“Cinders are usually red or reddish-brown with lots of vesicles (holes from bubbles) in them. Cinder is another name for scoria.” (All those holes trap air and make lava rock a good insulator.)
Image source: About.com
I’m currently seeing Lava Rock (Scoria) available from big box home stores. Unfortunately it would involve oodles of plastic bag waste to use these in building quantities. There is a website for “Featherrock” that advertises Pumice gravel in quantity, but does not look to have been updated recently. Anyone find other sources showing up?
I noticed that you can buy small bags (1/2 cu.ft.) of scoria at Tractor Supply for about $7 each… might be enough for experimenting.
Possible other places to scope out:
https://www.tororockproducts.com/
https://xerocolelandscapes.com/gravel-and-stones/
https://www.facebook.com/DecorativeLandscapeAndMaterials/
https://www.rhlava.com/
I just wanted to add some updated info to this. I have been searching high and low for scoria. Alaska doesn’t have readily available sources. I have contacted a long list of people and while we can find the volcanoes and a scoria pit even, there’s no way to get it to the general public. Which really frustrates me because I’m been hot on the trail for a long time trying to build an earthbag home for us. If anybody gets any bit of updated info, please share.
Your best bet then is to build a straw bale house. Bales are super insulating, easy to work with and should be available in many places. Search this blog for lots of information on strawbale building. One interesting design is called a straw bale yurt. The cold and wind would just blow around a small home like that and be real toasty inside. Thanks for searching for scoria and reporting back. This will save others from going through the same process.
Anyone considered gabions lined with material, then filled as you would a regular earth bag? Would probably be quicker to fill than earth bags. The rows of wire cages can be wired together for structural integrity in any number of shapes and configurations. Last, but not least, the cages could be sectioned off so insulating material could be put in one section for cold climates.
I saw they’re experimenting with them in Haiti, using rubble from the buildings that fell in the earthquake to fill the wire baskets, which are stacked and tied to make the walls of new homes. I saw no reason the baskets couldn’t be sectioned, lined, and filled with dirt in one section, then insulating material in the other.
Might be more expensive than earth bags, though. Still, building a sturdy structure with them should be possible. Another option is using them as support walls in in-ground structures. It should reduce the cost of concrete and allow local materials to be used. Back fill, drainage, and waterproofing would be done as normal for an in-ground structure. Gabion pillars could help support the roof.
Just an idea.
They have numerous advantages as you say. The main drawback is cost. They’re way more than earthbags.
I was curious Owen. I remember you mentioning that when building domes with cinders, the dome should be more vertical (steeper slope). How much steeper and how would one gauge it? Also has anyone used cinders that have been stabilized with cement? If so what percentage of cement would be used? Normally at CE they talk about 6-10% for sandy soils. Do you know of a recipe for a cinder based concrete or pumicecrete?
On another, but related topic. In areas of seismic activity, if one was to use a cement stabilized cinder or rubble filled earth bag foundation, how would one tie other courses of bags to it? Would the 4 point barb wire be enough? My concern is that in areas like Alaska, seismic activity needs to be considered. If one uses rebar stakes to reinforce the cinder filled bags, how would those bags be tied to the foundation? The rebar would be nearly impossible to drive into a cement stabilized rubble foundation after setting. Would the foundation bags need to be tied to the next course with additional wire?
A good source of information is the Bureau of Mines. I found that they list commercial and private mining operations based on the mineral resources being processed. People looking for cinders may find a supplier. The major problem I have found is that sometimes distance is an issue. Transportation costs can add up quickly.
Thanks
Kelly’s free dome building guide explains exactly how he built his scoria earthbag domes.
http://www.earthbagbuilding.com/articles/riceland.htm
I’ve seen a pumicecrete recipe on the Internet. They probably use around 8%-10% cement. Pumicecrete is popular is certain areas such as New Mexico and Colorado because the big scoria mines are down south of Alamosa.
You can tie earthbag courses together with baling twine in seismic areas. Normally this isn’t required, but seismic areas require some extra reinforcing. It’s also good to tie courses of scoria bags together in non-seismic areas for stability.
Thanks
I had reviewed Kelly’s guide before, but forgot to bookmark it. With the cinders would you need to change the slope to 60 degrees if you were stabilizing the fill? I wasn’t planning on a loft and the 60 degrees would make a 16ft dome pretty high.
I am not sure this dome was stabilized, but they did use cinders and it looks like they didn’t change the slope.
http://halcyontimes.wordpress.com/2010/09/12/progress-update-5/
http://halcyontimes.wordpress.com/2010/08/18/progress-update-4/
Thanks
You could curve the dome in more quickly if you stabilize the scoria with lime, cement or even clay.
It looks like the Halcyontimes foks used 24″ wide bags (it’s cold in Montana!). Normal bags are 18″ wide. The wider bags make it easy to curve the dome in more quickly.
The radius of their dome is probably outside the dome. This is the method Doni and Kaki show in their earthbag book. They go into lengthy detail about this and other dome building topics and so I suggest buying their book if you’re going to build a dome.
Correct me if I’m wrong, but wasn’t there a previous post on this blog about P.S.I. (or some other engineering firm) being willing to stamp engineering plans for earthquake resistant earthbag structures?
Seems like those plans my have been at least partially associated with the response to the Haitian earthquake?
My memory of those engineering plans was that they recommended filling the earthbags and using rebar pins and reinforcing wire on the inner and outer surfaces of the earthbag walls complete with ties running through the bag wall. Tie the inner and outer wall surface reinforcments together forming something like a custom formed gabion cage. All this reinforcement was then to be embedded in plaster and stucco layers to make it extraordinarily strong.
I tried to search for that old blog post here on your site, Owen, but I can’t seem to find it. I see several possible reasons why I can’t find it.
1. The different combination of keywords that I have attempted do not sufficiently match the blog posts in question, and therefore my searches do not yield the blog post(s) that I remember.
2. Blog posts have gotten lost in the web host switchover?
3. An evil corporate conspiracy attempting to censor important information that threatens their dominance of the building industry hacked in and maliciously deleted all references. This proves that the corporate overlords are worried and are afraid. Very afraid. Time for us to keep fighting harder to go for the jugular. ;) (kidding. I’m not much for conspiracy theories.)
4. I’m an idiot and my memory of that system is incorrect.
The site is so large now (over 1,500 blog posts) that it’s somewhat difficult finding things. General search phrases like rebar, etc. don’t work. The best keywords in this case are ‘external pinning’.
https://naturalbuildingblog.siterubix.com/external-pinning/
External pinning would create an extremely strong earthquake and hurricane resistant structure.
Yeah… that’s the general concept. That’s not the exact post I was thinking of, but it covers the topic very well. Thanks for finding it for me.
It seems to me that would be an outstanding method to produce an extremely strong structure filled with insulating scoria or pumice, but yet still more than strong enough to withstand the earthquakes common to volcanic areas.
I’m relieved that option #4 is not the case.
well… uhh…
I may still be an idiot, but at least my memory isn’t completely worthless. I’m relieved about that anyway.
You may be thinking of Precision Structural Engineering’s earthquake resistant earthbag wall system.
https://naturalbuildingblog.siterubix.com/reinforced-earthbag-specifications/
Again, if you don’t know the exact phrase to search for then it takes a while to find stuff. I look up stuff every day for people and so I know what terms to enter in the search engine. The key phrase here is ‘reinforced earthbag’.
You got it. I’m usually better at finding the correct keywords, but for whatever reason, I simply didn’t land on the correct ones in this instance.
This second one is the particular one I remembered, but both blog posts are very worthwhile.
Following the links in the second one takes you to the PDF file that really stood out in my memory. I just didn’t remember it as a PDF file.
http://earthbagbuilding.com/pdf/PrecisionReinforcedEarthbag.pdf
Seems to me that pdf file would be a nearly ideal resource to answer questions like the one Milton posed that started this whole thread of comments.
This post gets me thinking.
First. That list of cinder cones is just begging to get plotted on a Google Map. This could be a useful map for a variety of reasons. People might use that map to help them choose locations to start searching for land to purchase with few or no building codes.
Also, blog readers may start paying attention to specific locations in those areas where someone might be able to drive up with a pickup truck pulling a trailer and a couple of healthy guys with shovels to load ‘er up. I’m not suggesting destroying any natural habitats or stealing. What I’m suggesting is for people passing through or living near those cinder cones might be able find locations with easy drive up access where it is safe, legal, and possibly even beneficial to that particular spot of land for people to help themselves to some free rock.
Lastly, individuals may also begin to investigate which cinder cones produce the best rock for building. Which cones have the best insulating rock? Which cones have the strongest rock? Which cones have the easiest rock to work with using hand tools?
Perhaps you might even convince some people that live or are passing near some of those cones to collect a box ‘o rocks from a nearby cone and send them on to Kelly or Owen so that the rock from each cone can be compared in a more objective and scientific manner.
Over time, a nice database of the type of rock available and possible DIY quarry sites could be developed.
Can you imagine the following discussion happening?
“Hey Sweetheart? You know that vacation we wanted to take to the West coast next summer? What if we took the truck and the trailer along and brought back a load of scoria or pumice to help build our house with on the return trip?”
Might not be the most romantic activity for a vacation, but shouldn’t building your own house with your own hands and sweat be the ultimate romantic labor of love?
Get the lightweight porous rock with lots of air holes. It’s sort of like shoveling popcorn. It’s the ideal material for those working solo and those of us who aren’t built like linebackers.
These volcanoes may be locked up inside national parks, not sure. I’ll leave it to readers to seek out the details. Most likely the national park service has granted mining rights to a company and so it should be commercially available at landscape supply stores, gravel yards, etc. You might save some money by digging it out of a road cut, etc., but it sure is nice having it cleaned, screened and delivered by the dump truck load right where you need it. Scoria is a minimally processed material and so it’s usually not real expensive if you live near the quarry.
And as far as strength, most any porous volcanic rock is plenty strong enough. It’s more important to find the porous material so you’ll have good insulation value.
A quick Wikipedia search, and clicking on the links shows me that a few of them are not included in park land, but none of the ones listed there are road accessible. The closest I found in my limited search is Prindle Volcano, which is about 20 miles from Taylor Highway. Taylor Highway is gravel, and closed in the Winter.
http://en.wikipedia.org/wiki/Prindle_Volcano
Thanks for the input.