How far from a hill... Donkey?

[mountaindreamer]

Nothing to do with stoves (other than I plan to have at least one inside this,) but I figured people here might have some knowledge about this.

My site is a hill, slanting away from the road, but it's actually higher than the road. One of those where the hills go in every which way, and the road was dug into the hillside. It's a little complicated, but the main thing is, I need to know how close I can build to that road cut. It's a bit hard to explain since there's two different hills, so picture time!


This is the slope to the road, which is what I'm worried about. I don't know the angle nor exactly how high up it goes, haven't figured out how to measure that without having wings. The level sitting in the road is two feet, put in the picture for scale.


This is the clearing. The brown outline (sorry it's hard to see) is roughly where I'd like to build, and the arrows indicate that it's about 15 feet from the edge of where that would be to the edge of the road cut. By edge, I mean... Well, have a diagram.


Make sense? (the road's on the right, out of the picture.)

Since it's on a slope I intend to partially bury the building in the hill, which is shown by the diagonal lines.

What I want to know is, do you think it's safe to dig down that far (about six feet) that close (15 feet) to the road cut? If not, how far away, do you think?


This is what the soil looks like by the cut. Along the cut further down the road there's more clay, but this is here. I would try to figure out what's in the area I'd leave standing, but... I'd like to leave it as solid as possible.

Also! The proposed building plan. It's a sort of rounded and mutated rectangle, with outside dimensions of about 19'x16' at their widest points. The 16' is the dimension you would see in the cross section I drew, but I forgot to add it in. It's not too passive solar friendly, but neither is the site.

Anyway, if someone can help me figure this out, I'd be very grateful. I'd love to start digging to build as soon as possible. If you think you can give me advice but want to know more about the situation first, feel free to ask and I'll give as much info as I can.

Much thanks!

[Donkey]

Yikes!!
I really can't answer that one definitively by remote control. Depends on too many factors.

It is helpful that you have so many trees on the site. Leaving as many of them as possible between you and the road is going to be key. Also, the angle of the cut above the road looks pretty good, it seems to be at the "angle of repose".
15 feet of stand-off sounds good, and would probably work HERE, where I live, but it's really too hard to tell.

Also, a 6 foot retaining wall (as indicated in your drawing) is a major piece of masonry, NOT to be undertaken lightly. It's pretty easy to screw up retaining walls, especially in clay rich soils. It's usually advised that you get an experienced mason for retaining walls over 3 feet high. 'Course you know, that means money, unless you got a mason in the family.

What you need is someone from your neck of the woods with experience in the matter. Some old timer who's been there, done that and can give authoritative advice.

[mountaindreamer]

Well, damn. There's maybe five people that live on that mountain; one of them is rather unhinged, and I don't think anyone's made retaining walls up there. Beyond the mountain, population isn't terribly dense.

So this retaining wall would be of earthbag, with a membrane behind it, and then a big ol' curtain drain (in theory) behind it. Possibility for ramming rebar through the earthbags if that would do any good. It would also be curved into the hill. Would any of that help my case? 'Cause I have no idea how to find anyone who's done this kind of building around here, let alone with the same materials.

[Donkey]

Yep, curving the retaining wall will help. Also, stepping back each course by some inches will help. Also, plenty of drain rock behind and landscaping cloth. I wouldn't do the re-bar thing, can't rely on it to last.
Gotta keep the bags from the sun. UV damage comes fast with plastic bags, so you'll need to plaster 'em.

I dunno.. I don't much like the earthbag thing. At first it seemed like a great idea, I love some of the things that can be done with 'em. It's just that over time I like the bags themselves less and less.

[mountaindreamer]

Yep, plenty of drain rock.

As to liking the bags, well... don't suppose cob would work so well as an underground wall, hmm? And I don't intend to use cement, pre-used or otherwise, for a giant wall, so... Options are slim.

In your opinion, should I at least attempt it, or do you think it's a total suicide experiment?

Hell, while we're at it. You like the bags less and less. Worked with them? Do you think a timber-supported earthbag dome could support four feet of snow? Or a timber-and-something roof? I'd prefer to not have a big tall sloping steel roof. It's not too aesthetically pleasing, and would be visible from the road. We also have an abundance of trees, some of which could use to be thinned out so the forest isn't so choked, mostly about palm-width poles.

[Donkey]

Apr 6, 2010 16:57:43 GMT -8 mountaindreamer said:

Yep, plenty of drain rock.

Good, you'll need it.

As to liking the bags, well... don't suppose cob would work so well as an underground wall, hmm? And I don't intend to use cement, pre-used or otherwise, for a giant wall, so... Options are slim.

No, cob is not so good below grade, I would never suggest it.
Broken sidewalks on the other hand work REALLY well. I don't blame you for being against the idea though.

In your opinion, should I at least attempt it, or do you think it's a total suicide experiment?

I think it's worth a try.. I Would suggest an extreme batter, that is, stack the bags IN to the earth being retained by a lot. The bags have little friction to each other and will slide easily. I think the re-bar pinning will fail over the long term, moisture in the earth etc. will rust them out over time. Also, rebar is a pain in the butt to drive in.. I've done it with straw-bale building and it sucked there, I can't imagine better in earthbags. Barbed wire in between the courses will probably go the way of rebar, I'd do it anyway, just cause.

Hell, while we're at it. You like the bags less and less. Worked with them? Do you think a timber-supported earthbag dome could support four feet of snow? Or a timber-and-something roof? I'd prefer to not have a big tall sloping steel roof. It's not too aesthetically pleasing, and would be visible from the road. We also have an abundance of trees, some of which could use to be thinned out so the forest isn't so choked, mostly about palm-width poles.

Err... I've no doubt that a properly built dome can do that, without the timber even.. I'm just not that comfy with the idea of doing it with earthbags. If you live in an earthquake zone, you might want to re-think it there as well.

Yeah, I've got some experience with earthbags. Like I said, I don't like 'em much anymore, just one guy's opinion. To my knowledge, they've not failed on anyone yet, so 'yer probably in pretty safe territory. Just remember that they MUST be covered and protected from the sun at all times, plaster them IMMEDIATELY. Also remember that they have slick surfaces and WILL SLIDE around in a earthquake.

Round timbers are MUCH stronger size-for-size than square. Round pole construction is GREAT. Sometimes a little harder to joint together properly, but well worth the extra trouble.

[mountaindreamer]

Thanks. Apparently in all my refreshing of the page I didn't get this until now, but wow, lots of answers. Great!

Now how the heck do I make a dome? I don't have experience with that one.

[shane]

mountaindreamer,
The very first thing you should do if you want to build an earthbag dome is get the book Earthbag Building Tips and Techniques by Doni Kiffmeyer and Kaki Hunter. My wife and I built a dome sauna last fall using this method and it worked out great. We made some mistakes but learned a lot. This spring we have already started work on a new home consisting of five connected domes. For the sauna we used poly tubes. For the house we are using 20" x 30" bags. Cheaper. I love the earthbag domes beacuase of strength, durability, no roof needed, very little wood required and a lot of other reasons including super high thermal mass. Our saina and house project can be seen at www.canadiandirtbags.com.

[mountaindreamer]

Thanks Shane. I got the book out of the library not too long ago and started reading it, partway through. I'm a little stuck on where to get my bags. Your house project sounds cool! Look forward to updates.

[Donkey]

I've gotten rejected feed bags from the factory. There is a percentage of bags that slip in the printing process and have the labels all wonky. You can get 'em for a cut rate.
Otherwise?? Dunno.

[shane]

I bought some misprinted bags for 20 cents each and got 100's of bags from local microbreweries for free. They were glad to supply them for something useful instead of hauling them to the dump.
I forgot to mention that it is a pocket rocket style stove in the sauna for now. I ran out of time in the fall to install a decent rocket stove but will soon. However the one in there currently raised the temperature from -20 C to +30 C in about 15 minutes.

[canyon]

Hey mountaindreamer,
Looks like a cool project. Soil pressure is very real and needs serious strength to combat. Each increase in depth is a great increase in pressure. The earthship system has figured out what works for rammed earth in tires. Earth bags do not even have anything approaching the same strength as tires and IMHO should not be used unstabilized below ground level. I personally don't want tires in my abode so I can relate if you don't either. Look up masonry walls or underground housing to get an idea of the different strategies for combating the forces at work. Gravity mass wall might be your answer with a tapering work of art of tight fitting dry laid stones from the area. Just my two pennies.

[mountaindreamer]

Love all the input! My issue is this: my site is accessed by a mile of unpaved rather steep road I'm already a bit terrified of driving. Then there's the issue of there not being much construction nearby (not really a complaint!) so if I used urbanite I'd have to haul it, quite a ways, and a lot of it for a wall like that. We've got a small staircase out of tires up to the outhouse, but I wouldn't know where to get that many tires quickly, not to mention the lack of appeal of tires in my walls.

Sadly, I'm waffling between going for it and trying to do it this Spring, and shoving those designs onto the back portion of my desk and starting from scratch on a different little clearing that is a lot flatter, but I'm less in love with.

I do find it a little amusing that I've managed to bite off so much more than I can chew. Usually my habit is to play it safe in life, it seems, but this, this is actually a little funny.

Oh right. And stones from the area would have to be dug up or grabbed from the creek bed, which I won't do. They're also either very round or larger than I can lift and so oddly shaped it'd take a master to make a wall with them.

[Donkey]

Do you REALLY have 6' of drop over the length of the building?
Cob and earthbag CAN be stepped up a slope, there's just a practical limit. Each step needs to sit on a level or even tilted back piece of subsoil. Earthbags will need to be stabilized or gravelbags below grade, AND one course above. Urbanite would do as well, though I hear your reasons for not using urbanite.
Then the slope inside the foundation can be filled to level (or close) with gravel and an earthen floor topper. Depending on how deep the fill is, your foundation (earthbag, urbanite, stone, whatever) would need to be built like a retaining wall, stepped in, etc.

If yer stuck with the site, you can plan for a split level floor, which will help if the site is just too sloped to fill-to-flat practically.
The thing with buildings that sit into the ground, drainage is ALL important and building on a sloped site helps here a lot. Best policy for cob, adobe, stone, concrete and earthbags.

[mountaindreamer]

Well, I had originally intended to build a split level deal, but never got any remotely straight answers on how to work the drainage on that. From top of soil to top of soil, I measured about a one foot drop for every four feet out. Once I get to subsoil to build on, that's even deeper, so... My other thought was that if I bury it in the hill as one level, it'll be less visible from the road. The intended contents of the higher-up-the-hill part of the house are the bed, toilet-thing, and bench, so the ceiling wouldn't need to be so high, with the kitchen and sitting/standing/dancing/whatever space further down the slope, so the roof would level out and provide those heights easily.

About the below-ground earthbags. I plan to use normal material but with an impermeable membrane on the outside of them, then drain rock, and below the wall a regular rubble-trench deal. Still need to be stabilized? I don't think the gravel would compact enough to stay put, would it?

When I'd been thinking about going split level, my other concern was where to split it. It's so small and the space is so shared between functions I'm not sure where I would do it. I'll see if I can get a copy of the rough floor plan on my computer and see if anyone's got ideas on that.

I know when I hit reply instead of using the quick reply there was a picture I intended to put in here, but I can't for the life of me remember. So, here's a shot I took last time I was there.

This is the edge of the hill as seen from standing in the road. The pink marking tape is wrapped around a cut down sapling and held at a height that would represent the highest roof I'd be willing to have. I wanted to see how visible it would be from the road. It's not held in the center of the building, but oh well. Anyhow.