Another earthbag idea

Undergound...I think i have found a cost effective way to excavate.  I want to build a rectangular building - no, not round - underground house about 5m x 17m.  Round and quaint, stronger than straight walls, but is less efficient use of space - how many beds or sofas have you seen with a round back to them?  This would require come berming - can do some outside but also inside, to make partitions for the rooms.  To make it water resistant, if not water proof...i was thinking, once the walls were in place, to rent a nail gun and shoot 4" or longer nails into the outside, then spray the outside with something like bedliner (for a pickup truck)...put a layer on that is only 1/4" or so, then add some kind of rebar, and shoot it with insulation, then finish it off with a cost of something that will protect the insulation and backfill.  Some of the materials are not very eco friendly..any thoughts?  The roof will be arched, with at least 1.2m of soil on top.

Hey Tom, I can see where you're coming from.  I've thought about many of these same questions myself.  I think you are drastically underestimating the difference in load bearing between a round and square wall.  Earth is not rigid, it heaves and withdraws.  As a point of reference, shipping containers are made of steel, with 4" steel frames at regular intervals, and they are unable to withstand the pressures from being buried.

As to your questions, how many sofas have I seen with round backs?  I'd say about 5% of the sofas at the furniture thrift store near me have round backs.  Mostly Victorian style, but also many contemporary (lazeeboy style) and Modern.  They also have matching side chairs with rounded backs.   That's definitely not the majority, but I could go right now and have my pick of a few sofa sets.  It just depends on what you're looking for.

Beds and cabinets, hardly any of those have round backs.  But I just ask myself these kinds of questions, which have led me to prefer round homes:

Let's say I have two weeks free.  Would I rather spend that two weeks in engineering tasks trying to make an underground square home structurally sound and survivable, or making custom furniture?

Let's say I have $5000.  Would I rather spend it on beams, cross-supports, bolts, and concrete?  Or splurge a little on nice hardwoods, memory foam, and fabrics for my furniture, and have $3000 left over at the end?

Do I want my kitchen cabinets to be rectangular and hold 100 cubic feet of storage, or half-moon shaped and hold 166 cubic feet of storage?  Or, stated another way, have you ever wished your kitchen cabinet was a little deeper?

I understand that round homes seem unnatural to many people.  The lack of straight surfaces makes placement of furniture or other things difficult.  In that case you can spend the $5000 and two weeks to get a square home or spend a few hundred dollars and a few days to make internal stud walls with sheetrock if straight walls are important.  The bonus is they'll have a nice storage area behind them.

I like how you are considering alternative materials for waterproofing.  I'm not super familiar with sprayable bedliner but my understanding is the bedliner is polyurethane.  If so, it is meant for abrasion resistance on rigid surfaces. It's not flexible and will develop cracks.  It only takes one crack and then you have water in your house. I think a better alternative would be a pond liner.  It is made to prevent water leakage due to heaving earth. Cheaper too, and arguably more green.

Rob Lineberger wrote:

spend a few hundred dollars and a few days to make internal stud walls with sheetrock if straight walls are important.

Yes, there are people who've made cob houses with no straight interior walls, but a good many plans use either cob or stud walls in areas to create noise blocks or privacy, and these can form "straight" locations for standard cupboards/fridges to be located against.

I've read a few interesting articles about the down-sides of "open concept" homes - I *know* my kid shuts the door to his computer area and puts hearing protectors on when I start my mix-master! We have a number of "pocket doors" that aren't in the way when open, but provide some noise dampening when closed. This is a good reason for those "straight" interior walls to also have a little insulation or mass in them to help "noisy" jobs to stay isolated. Similarly, it means if I burn something (I'd *love* to know where that greasy stuff at the bottom of my oven came from) I can close the two doors, crack open the door to outside and turn the stove fan on and not have the rest of the house smelling smoky.

I would love to live in a round home, and preferably one where the ceiling heights weren't all exactly 8 ft. But I wouldn't exchange that for "cathedral ceilings" that I can't clean the cobwebs off either. I highly recommend, "A Pattern Language" (Christopher Alexander) for anyone who wants to plan their own home. Yes, you aren't likely to agree with everything he says, but it was a book I read years ago that got me thinking about how very much we are conditioned by what's around us to accept that as "normal" and "desirable" when it's really more - that's what's cheapest for the builder to build.

As for Tom Connolly's idea - have you looked/read all the threads about earth bermed WOFATI style buildings? Controlling water is *everything*. They do it more by building up and then covering it like a mound rather than excavating down in an effort to make sure they can control water run-off without having to overdue expensive or polluting materials. If you need the dirt, that's what digging a pond is for!

Thank you both for your excellent answers! If things work out, it looks like I will be able to build into the side of a hill, so excavation would amount to slicing a part of the hill off, as well as digging a few feet down (this is still slightly up in the air, but land with hills on it has been a high priority on my list for 20 years.  I could probably still work a round structure into the plan, or at least curved walls.  The original idea would have 3 earthbag walls as interior walls, about every 10-12 feet or so, and maybe 3 berms built into the hill, offsetting the interior earthbag walls. I have also thought about some pyramiding half height berms in the front to separate the "yard" into a couple of parts.  Water?  Water???  I wish.  I participate in a forum of people that live in the area.  Some have dug down as far as 12 feet and have yet to find anything that resembles water.  

Tom Connolly wrote: Water?  Water???  I wish.  I participate in a forum of people that live in the area.  Some have dug down as far as 12 feet and have yet to find anything that resembles water.  

As they say in the Real Estate business, "Location, location, location." In the winter our lower field turns into a pond if we have a big rain, but I *still* have trouble getting it to soak in deeply due to the rock and clay content, although it's way better than when we moved in. I don't know what management practice (maybe beavers?) would help in your eco-system, but there's lots of "dry-land" permaculture happening world wide with great results, so try not to loose faith!

Look closely at earthships and how they buttress the back wall to hold the berm, and those walls are three foot thick and it's an above grade berm, not a full hillside.

You can hide those buttresses in walls, and you can put deadman anchors into the berm.

There aren't many nail guns that can shoot 4 inch nails, I doubt you can rent one.  And gun nails nearly double in price to go from 3 inch to 3 1/2. I haven't even checked the jumbo nail prices.

There are elastomeric coatings that will stretch more that bed liner, but they are pretty expensive.  A spray coat of something to stabilize the bags from decay would be a very good thing, but I would count on it as waterproofing. It it's pretty impressive what spraying line x on sandbags and hesco containers did in Iraq.