Gregory Pappas

Mike Cantrell wrote:Very cool! What's inside?

Thanks. Nothing's inside. We built this to see what building with earthbags was like. Apparently there are tons of scorpions, spiders and snakes living in it now!

Christopher Steen wrote:Scoria is insulative. It is thermally valuable in climates where you want your interior temperatures moderated from exterior temperatures. Thermally it makes the most sense to have insulative exterior walls and mass interior walls, with the exception of those areas which are hot during the day and cool off considerably at night, and have decent cold season solar gain--those areas comfortably allow straight mass exterior walls.
Nonetheless, thick mass walls work wonders in hot climates especially if shaded with deep roof eaves (which are also good for natural foundations/walls in rainy environments). EB walls are substantial.
Yes pure Scoria bags are lighter and quicker. Offset that with costs--material and labor. If only a few workers or have other jobs then Scoriabag may make more sense. If this is a big group effort, then maybe show them pure earthbags.
As for mixing Scoria aggregate and clay/sand: don't think you Get the best of both worlds, insulation and mass simultaneously. That's the WRONG REASON to combine. Thermally, It'll just perform as mass. It will lighten the load a bit though and labor should increase as a result.
Also I disagree with the previous comment about it not binding. It'll bind with appropriate clay content as well as the larger aggregates mechanically locking in together. So maybe determine your clay content. If it is high, either cut with sand or Scoria or gravel. Start your tests from 3 aggregate : 2 sand : 1 clay. Which for a high clay content dirt could mean 1 Scoria: 1 high clay content clay-sand dirt. Why did I say gravel? Because we are not talking about some tensile strength here, bag fill is not the tensile stuff of ferrocement or fibers or steel cable. We are talking about compressive strength mass wall construction. It is not monolithic, it is a bunch of tamped bags. The importance here just as much plaster work, I believe good distribution of aggregate size makes sense. All different sized aggregates tamped and locked into place by both clay binder and aggregate distribution. Yes its overkill to state this and to even apply over a regular screened earthen fill but you asked if "there was any practical value to combine Scoria (lightweight larger than sand aggregates) to clay and sand even though you don't receive pure Scoria insulation values". My tests showed that bags with larger and more diverse aggregate performed better--less water usage, quicker dry/hardening time, higher compressive strength, more stable without the bag (and all sands and clays and gravels and scoria have different properties and respond differently--so test each soil). A few times I have seen this combined for the WRONG REASON (thermal performance) in my cold climate, so I must spell this out here for future googlers.
I believe larger aggregates in earthbag fill makes better earthbags; better Scoria aggregate size distribution makes better scoriabags; and logistically (labor or cutting down clay content) the inclusion of Scoria could make the jobsite more efficient. Depends upon mixing methods, material and labor cost, clay content. Doubtful you'd notice any difference in thermal performance from earthbag and earth-Scoria bag mixed at previously stated ratios although it does lighten the bag somewhat.

How do partial scoria filled bags react in walls if needed to be drilled or opened for any reason such as plumbing, or piping through?

joey melroy wrote:Hi all this has a couple parts to it. I am going to build in Nicaragua where it is Hot year round. Bone dry six months and rainy six months. I think Scoria (porous volcanic rubble) is available and cheap here. Clay and sand are also readily available.

I have seen sand clay mix recommended in hot climates and also pure Scoria bags for good insulation in cold climates.
Could Pure Scoria work in a hot Climate as well?

Very good question. I have built an earth dome in Honduras and we used a sand/lime/cement mix for our outer coating/plaster. We used cement because we didn't have time/money to put a roof on it, and the whole project was to try out the wall building technique, not much more than that. I can say that on a very hot day, stepping into the dome felt like stepping into a room 10-15 degrees cooler. And at that point we hadn't put any windows or a door on the structure. I'm going to be in Honduras again next month to build a 2 bedroom home using earthbags and was pondering the same thing. I think it'll help regulate the temperature of the home, regardless of whether it's in a hot or cold climate.

For walls on a home is it practical to use Scoria as an aggregate mixed with a clay sand mixture to help lighten the bags?
This will be less insulated when the pores are filled with sand and clay but could this still have practical value?

I wouldn't recommend using scoria for wall building. You want the clay/sand to bond to more or less create giant adobe bricks. For the same reason, you need to thoroughly sift the soil before filling the bags for the wall sections. Again, it's my opinion, but I can't see the sand/clay ever being able to create as good a bond with scoria added to create a well stabilized bag. You may want to make a few test bags, pound them out and let them sit to dry for a few weeks. Then run some tests to see how strong/stable they are.

Another question is are Earthbags practical for a wall at the perimeter of the property?
This will obviously be exposed to the elements with no roof so maybe sand/clay mix is not practical.
Could I use Scoria bags for a property perimeter wall and use a cement stucco in this case?

Any advice would be greatly appreciated!!

As far as walls for the perimeters, I've seen many in books. Usually the photos are of homes in Arizona and other dry climates that don't get much rainfall. What they're filled with I don't know. It would make more sense to fill those bags with scoria and use a cement stucco to cover the bags, as water absorption/retention (due to the cement) wouldn't be an issue. Also, the scoria (nor the poly bags) won't be adversely affected by the moisture. What you absolutely must pay attention to is the poly bag exposure to the sun. When I first started my project in Honduras, we used a giant blue plastic tarp to cover the foundation gravel bags. We used blocks to hold the tarp down but one weekday (we were only working on the project on the weekends) the tarp was blown around a little and just a small corner of a bag was exposed. Within the week span of being exposed to the sun, the poly section literally turned to dust and the gravel was spilling out all over. (we forgot to double bag the foundation). If you use unstabilized scoria, you could run into the same problem, especially with the intense sun in Central America. Like I said earlier, I'll be in Honduras next month building a home, which is on the same property as my test dome. I plan to cut open large sections of the cement/lime/sand plaster to see what kind of moisture was absorbed and retained. I'll be testing sections of the bags as well to see for myself whether or not cement is the enemy of earthbags as I've found in my research.

When do you plan to start your project? What part of Nicaragua? Would love to hear more about it.

Ash Medai wrote:In my readings on earthbag construction (or other masonry) and earthquake resistance, is the use of wire mesh (chicken wire) on both the inside and outside of the structure, and connected between the walls.
The wire needs to be pulled tight to prevent motion of the masonry or eathbags. When properly applied, this method far exceeded the california earthquake testing equipment. That said, Im not an engineer and cannot educate you on the proper way to build. I mention this to give you a starting point for your own research. Please consult a professional engineer in such a high danger area.

Wire mesh, especially on domes, is tricky to work with. It slowed my team down quite a bit. We used chicken wire more for plastering purposes than wall strengthening. After we completed the walls, I realized that the walls and structure as a whole was and still is extremely robust, with or without the chicken wire.

I did read about another technique used in the book I used for my construction which involved lacing the layers together by using barbed wire hung from bricks and slinging them over each layer. It's a poor description, but is fully outlined in the book. If stability was a larger concern, I might consider doing something like this. It would add quite a bit of time and materials to the project though.

I'm still not getting it. You can include wood plates between the bags and have them sticking out as attachment points for framing outside the dome. From there you can attach a more traditional style roof. I don't see the need for poles for anything.

Hi Patrick,

Can you better describe or make an illustration of your issue with the poles? I'm not following.

As far as earthbag construction books, I still feel that Hunter/Kiffmeyer's "Earth Building" book is the best out there. I used it for my project as someone completely new to earthbag building and my dome came out relatively good.

Have you done a simple jar test to see the composition of the soil?

Glenn Herbert wrote:You can build an earthbag dome and it will probably be strong and hurricane-resistant, but unless it is reinforced with steel according to professionally-calculated designs, it is likely to collapse in an earthquake and kill anyone inside. Concrete mixed with the soil will make it stiffer, but steel to tie it together is the only way to guard against the bags slipping and falling in strong shaking.

Go ahead and build a small dome to test, and see what it feels like inside in your climate. It may be more liveable than the local standard, or it may be less, I don't know. How much have you studied earthbag domes? What references do you have for safe dimensions, slopes, thicknesses, etc.? Do they consider earthquake resistance at all?

I recently read Bingham's book and follow her blog. Her new construction survived 4 earthquakes from 5.2-6.1. Her construction is a round house, which I feel would be more suitable to withstand earthquakes over a dome. Also, she did not use any concrete in her bags. http://www.themudhome.com/earthquakes-and-earthbag.html

Dr. Gieger has a number of articles on his sites concerning earthbag constructions and earthquakes. I would look around that site some more.

Hey all. Just found the site and thought I'd contribute my fairly recent project.

I was living in Honduras from 2012-2014, working as an English teacher. During that time I built a 14ft. diameter earth dome on a friend's farm as a bit of an educational experience. The dome was completed in 2013 and is still standing strong today, despite the lack of a roof and absolute abandonment in all respects. I'm back in the USA now and will be returning to the same area in February to build a 2 bedroom/1bath/1 living home for the caretaker of the farm where the dome currently resides. I'll try to make a post when I get back in March/April with some photos from the project.

This is the complete gallery from the dome build: https://flic.kr/s/aHskaDtV8V

Mr. Pappas With His Project by Greg Pappas, on Flickr

Mud Being Applied to the Earth Bags by Greg Pappas, on Flickr

Mud by Greg Pappas, on Flickr

Outer Mud Layer by Greg Pappas, on Flickr

Final Coat by Greg Pappas, on Flickr

I have some experience with earthbags and can offer my .02 based upon what I've learned while building a 14' radius/15'ish tall dome. Mind you, I built this in tropical Honduras, so my needs were a little different.

As for a universal lesson, I would say that building a dome is probably much more difficult to construct than a square/round house. The curvature of the form needs to be measured very accurately and be very precise. Any errors in this department and you run the risk of the dome collapsing. For your first construction, I would stick to a round or square design.

I have been working with an architect to design small homes for upcoming projects in Honduras and he is an advocate for a square design, while I like a cylinder. With his CAD drawings, he's been able to show me a lot of dead space that is created in a round house due to things like beds, furniture, etc all being square. On the flipside, a round house doesn't need buttressing around the walls and as a structure is much stronger than rectangle or square.

If cost is going to be a restriction in this project and you're trying to maximize usable space within the structure, I don't know that I would recommend a free form design. It will require more labor/time intensive founding digging and most likely more materials.