If it were me, I'd consider climate, soil composition, moisture, topography, access to suitable earthbag fill, and the loads that it carries ( eg. 12" thick single wythe stone masonry, one story tall, etc). We're you thinking about plastering the exterior side of the EB, backfilling with drainage stone, or adding a membrane?
I'm not an engineer but have a good working relationship with EB. If you want free structural and construction advice, then what are your structural conditions, anticipated basement uses, priorities, resources?
(depending on reasonable soil conditions, I'd be comfortable doing what you propose, with regular 50lb bags, however there are larger sizes... If soil conditions, climate, no termites, swayed me, I'd also be just as happy with icf for the basement which depending on your stone wall thickness, could be only 5-7 times the concrete as your 12"x18" bond beam...)
I have a lifetime in conventional building, and my rule of thumb is to make it stronger than you think it needs to be. "It might work" is a tad cavalier when considering potential catastrophic failure. A bed in the basement? I wouldn't sleep too soundly, myself. The worst case scenario makes it a foolish gamble. Actually, the other way round is ideal; rock basement, EB domicile atop, but you seem set.
I can believe that polypropylene earthbags would hold the instantaneous load of a stone wall above, but I expect that the fill would never dry out and truly solidify, rather creeping under the load and possibly eventually stressing the bags too much. How many decades do you expect the bags to retain their full strength?
How many houses in your area have basements? How many have living space in the basement? I suggest you investigate that before building.
Yes, it ups the cost factor, but this is a permanent dwelling you're shooting for, and some chances are not worth taking.
nick bramlett wrote:If hate to bury such prettiness.
It seems like I've seen a style of house with stone up quite a ways and then plastered above...covering something...might as well be earthbags?
Your family will see the stone work in that room from the inside and appreciate...good craftsmanship is good craftsmanship whether anyone sees it or not.
Either way this sounds like it will be a beautiful home...
An oval basement wall would obviously be stronger than rectangular; just don't try to cantilever the upper wall at the corners as this would likely cause cracking. I would transition the exterior of the foundation to rectangular over several feet of height so the exposed walls will be well supported all around.
nick bramlett wrote: I'm 45 minutes outside of atl ga. Humid and hot. 50 inches rain/year. Sandy clay soil. Plaster inside, no plaster outside, just a couples sheets of polypropylene sheeting and the back filled with same sandy clay. Bags would also be filled with sandy clay. Single heavy duty 18x30 bags. Thinking of making earthbag section a 12x16ft oval meeting up with 12x16 oval stone which squares up to 12x16 rectangle as it nears roof.
Nick, hey I forgot to check back on your forum post. My building experience is not in your climate. But I believe a few things with regard to your climate:
1. Insulation needs to be on the outside of your basement mass walls/floor to prevent dew point and moisture from condensing there. I believe this is a big reason for many moldy earthen projects above grade and basement funk.
4. Backfilling basement with clean aggregate, appropriately sized. Not backfilling with clay.
Is your clay expansive, does it crack it slabs and basements and block crawlers in your area?
5. Mechanical ventilation or drying in basement.
Should all be pretty standard in your area.
6. I still stand by ICF basement under your stone hut. Hey it's 12x16. 14 block per course if you cut and glue your corners. I could have stacked them in the time that I spent typing this out. When it's all done, that is just a drop in the bucket
7. Hey I love good mass in a house. I also appreciate exterior insulation. If your dead set in single wythe stone exposed on both sides, then some diy icf downstairs might be welcomed for a number of reasons.
8. Your water table sounds like it could rise in a heavy rain. then again, I don't know your topography or drainage plan. Maybe I just see too many areas flooding in the news recently.
It could work, I stand by it. And I have high levels of acceptability. Depends on lots of site and construction details. I could bang it out and sleep soundly down there till the day I die. But considering all this talk of diy squinching an oval footprint into a a rectangle, already using concrete in your grade beam, high humidity, rainy clay area, high water table, clay backfill, guess work, I'd suggest you to just pour icf, I would without a thought if I was out your way. Then deck over that and be happy. Backfill and grade correctly. That icf won't cost much; over it's lifespan, it's footprint is justifiable, moreso than a slab. But I'm of the 'concrete for walls and roofs rather than floors' mindset. That's my free advice from a nut builder hanging around this forum. And I love earthbag, don't get me wrong.
To me, an earthbag basement is like an earthbag dome, awesome is the correct setting. Many materials can be used awesomely and correctly, but materials are also often used in situations when better options exist for that particular set of conditions, a trade off typically due to cost, time, availability, labor, ideology...
Or if you really want to have an earthbag basement, then have a good mix, , good high site, good drainage plan, and good backfill, and be prepared if you need mechanical ventilation or dehumidification.
If the basement is too daunting, rubble trench that clay and grade beam, and don't look back.
I like Glen's point about moist sub grade earthbags creeping under load over time. Aside from flood, I think if you have that kind of moisture, you would have serious mold issues already. I also think his honkin grade beam would not produce much creep. Plaster cracking due to wall creep settling don't really seem like an issue in eb, sb, re, Adobe, or tire construction. I haven't seen any. Not like drywall cracking, etc... Wood moves way more, though that's more a hygro-thermal deal. Plaster cracking in these wall methods is typically from lack of shear, or lack of reinforcement around windows/doors. Or bad mixes, attachment, cure, freeze thaw, weathering, etc. Plaster cracks in settling earthen walls would be apparent. Never saw any in the pueblos. Heck, the adobes under lake Mead look good still.
Joseph Lofthouse wrote:The foundation of a building should be the strongest thing in the building, instead of the weakest. Doesn't seem prudent to build a stone building on a plastic/clay/sand foundation.
I bet 99% of stone buildings were over lots of clay/sand. All but those over bedrock.
If he excavated Adobe to pour a concrete foundation, there will still be Adobe underneath his concrete. His proposed grade beam over the earthbag wall is a good jumbo foundation, not chincy....
Many unreinforced stone masonry buildings succumb. So do reinforced concrete. So do earthen. So do framed. A well built earthbag foundation, wall or roof is nothing to sneeze at. Especially comparatively.
People do masonry over wood, everyday, everywhere. I think they are nuts, but it is done. Different expansion rates and wetting tolerances and elasticities. That doesn't seem prudent.
If moisture is dealt with appropriately, a good rammed earth wall can carry way more weight than he's taking about.
Most of the houses I've seen with foundation problems it is the sub structural medium that gave way and caused the settling. Clay will not do as well as sand when it comes to supporting a heavy structure, the clay will squish where the sand simply compacts.
This phenomenon can be observed in England's St. Paul's Cathedral, when construction started, the architect decided to go with clay instead of sand and that resulted in an almost 3 foot sinking of parts of the foundation.
The idea of earth bags would be best for above the foundation building simply because the bags will most likely fail due to pressure of the structure above them.