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#1 EtdBob

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Posted 09 June 2009 - 01:43 PM

Well, it was time to replace the old tool shed.
Despite all the framing I'd added, the serious snow loads we get up here had finally damaged our old Montgomery Ward metal garden shed beyond the point of no return.

The wife wanted to throw up a simple pole shed, using up all the scrap lumber we have laying around. I wanted to add on to the cordwood wood shed using more cord wood and mortar.
I didn't want a crappy metal clad pole shed in my back yard, and the wife didn't want to put the effort in needed for mortared cordwood.

Also on our list of things to eventually do is build a ferro-cement dome for use as a guest cabin, and my wife was bugging me to get rolling on that project. So, we decided that a ferro-cement tool shed would be a good introduction to this building technique, letting us learn ( read that as make mistakes ) on a smaller scale non-critical project. If this shed holds up to our snow loads and is water proof, then next year we'll build the dome.

My contribution to the art of ferro-cement building is the use of inexpensive 16' long cattle panels for the frame work.
Ever since I first transported a few of these panels bowed up in the back of my pickup truck I have been fascinated by their potential as building material.
The steel is stiff and springy, easily bowed into useful shapes.
Barrel vaults! Domes! Covered wagons! Simply had to try it out.

The cattle panel frame -

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We used the better part of three full panels to frame the shed up.
I'd intended to weld it all together but simply wired it up instead, because I couldn't get the welder I'd borrowed started!

We had a small cracked 7' x 12' concrete pad where the old shed stood. I dug a trench around three sides of it, maybe four inches wide by six deep.
The cattle panels were cut to length with bolt cutters. One end was shoved down into the trench, the other was nailed to the woodshed. The trench was filled with concrete to lock the panels in place.

The doorway presented a problem. It simply had to be sturdy enough to maintain it's shape when the cattle panels were nailed to it. I framed one up of 2x4s and that didn't do it. The next I framed up of 2x6s, and that didn't work. Finally I set two cedar posts in concrete, and that worked fine.
The rear window frame simply rests on the cattle panels and is wired in.

The cattle panel frame is covered on the outside with chicken wire, and a layer of 2.5 pound lath on the inside.

We soon discovered that the job of tying the chicken wire down and the lath up was a real chore!
First you cut a pile of short lengths of stiff wire, bend them into a U, and someone pokes them through from one side while the other person twists the wire up with pliers. Because of the huge number of ties needed this is a big job. It takes a long time and your always poking yourself with sharp bits of wire.

My wife had the wonderful idea of using plastic wire ties instead of bits of wire. Once we started doing this the tying went several times faster.
So, this handy tip is her contribution to the art of ferro-cement building!

Tying the top portions of the covering was difficult because you can't walk on top of the frame. We had to lean off ladders, or lay on the roof of the wood shed to get the job done. I have no idea how to do this with a barrel vault or dome, unless one uses expensive scaffolding.

Ties everywhere! -

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The finished frame, chicken wire outside and lath inside -

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Now it was time for plastering. I used a standard ferro-cement mix of about one part Portland cement, one part water and three parts sand. I used 1/8 inch minus sand that was available locally. Masons sand would probably work better. I was hoping we could get away with one layer on the exterior, so we dribbled some red cement coloring into the water as we mixed.
Yet more ties had to be added here and there to prevent the chicken wire from sagging.

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The adults on my volunteer plastering crew thought I was crazy, and complained of to dry a mix, to wet a mix, it isn't sticking, dropping more on the ground than getting on the wall, and why-can't-you-build-normal-stuff-like-everyone-else-anyway? In other words, all the usual adult hang-ups.

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The kids had no trouble and dove right in. Being kids, they still knew how to play with mud and have fun.
I had three adults and two kids plastering, and a lady measuring out water and Portland.
Naturally I just strutted around, swilling coffee, waving my arms and shouting "Plaster me hearties plaster!!"
OK, so I was really shoveling sand and mixing the whole time...

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After about a hour we stopped for a coffee break. When we got around to getting back to work the crew went into overdrive and I didn't turn off the mixer once, I could barley keep up with them.

At one point the weight of the wet plaster started to buckle the cattle panel frame. "Shhhh, don't tell Bob!" was the instinctive reaction of the hardworking, dedicated and professional crew, but my loyal wife, who also had to live with the finished product said "Go get Bob go get Bob!!
We had to shore the interior up as we went along. I had really thought the stiff bow of cattle panels would hold the weight.

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Plastering the top was just as hard as tying the top portions had been, because you can't climb on the surface. But toweling down the plaster got easier the flatter the curve got.

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But eventually the job was done.
This is what the interior surface looks like. I had originally experimented with using burlap material for the inside covering but couldn't make it work out, so used the more expensive metal lath. I'm glad I did. The walls were flexible enough as it was which made plastering difficult on the vertical walls.

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It rained that night, perfect weather for curing cement, but the shed proved to be full of holes. I'll have to add another layer to the outside.
The shed is now nice and rigid.
The inside gets a layer off stucco if I can mix stucco that will adhere upside down, or gypsum plaster. Then a coat of whitewash to brighten things up.
I have a nifty semi-circular window to build into the door.

My new mud hut -

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#2 purple

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Posted 09 June 2009 - 03:06 PM

Thats cool. ;) I am glad you posted the photos and I may have some questions later as I plan to build something using this method later. Thanks Bob.
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#3 Geo

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Posted 09 June 2009 - 03:58 PM

Interesting post as always, Bob.

If this shed holds up to our snow loads and is water proof, then next year we'll build the dome.


Hopefully this winter won't be as bad as last winter; you guys really got dumped on. Maybe the curvature will help it slough off snow.

Covered wagons!


There is such a thing as taking the old school thing too far. ;)

volunteer plastering crew


It's good you're showing others the Way of the Self-Reliant Man. Also, nothing beats slave, er, "volunteer" labor.
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#4 Mike

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Posted 09 June 2009 - 04:16 PM

I'm glad you posted the photos too because I apparently had no idea what you were using those plastic tie-wraps for. Yeah, that ought to hold up just fine. And it's cool lookin' too!

#5 Tobus

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Posted 26 June 2009 - 08:52 AM

As I was reading your post and you were talking about the cattle panels being too flimsy to stand on when installing the ties, I was wondering why you didn't shore it up inside. But it looks like you figured it out when you were putting the ferrocement on.

When you get to building the dome, I would just go ahead and shore the inside from the get-go. Shore it in several places, and even use horizontal struts (as well as diagonal bracing) on the inside to help the panels keep their shape. That way you can climb on it and it will hold its own weight until the concrete is cured. As a general rule for what you're doing, if you can't climb on it, it's not going to hold its shape when you cover it in wet concrete. Might as well go overboard with the shoring in order to ensure stiffness of the frame during placement of the concrete.

So did you ever get the leaks patched up? How rigid/sturdy is it now that it's cured? Would you say it's strong enough to walk on the roof?

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#6 EtdBob

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Posted 26 June 2009 - 10:42 AM

I kicked the supports out after about a week. The shell is quite rigid now, and you can walk on it.

We discovered that additional coats are pretty easy to apply if you get the plaster consistency just right, and Heidi and I have finished up the exterior by ourselves.
We put a second coat on the vertical surfaces, then a good thick coat on the "barrel" to waterproof and fully cover all the chicken wire. Sadly, it then began to rain and that coat of plaster didn't like that. It dried with the color washed out and a sandy texture. So, Wednesday we put a third coat on the barrel.

Last weekend I built a door, and this weekend we will plaster the interior with Red Top gypsum plaster. For economy I'm still using cheap 1/8 inch minus sand that is available locally at 15 bucks a ton instead of fine masons sand which is what your "supposed" to use with stucco and plaster mixes.

Eh, I did throw in lime, about four soup cans worth, into each exterior plaster mix. Otherwise I followed the "standard" ferro-cement mix of 1/3 portland/sand.

I reckon the initial plaster coat was about a ton, but that weight was very well distributed over the whole surface.
I figure if it had been a proper barrel vault like this -

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It would have held up fine. But how do you plaster it??

But yes, if we do a dome It'll certainly be braced up on the inside. I still doubt one will be able to walk upon it during construction!
Any vibration will kick the wet plaster through the mesh. Walking upon the chicken-wired-surface will rip or distort the wire, especially since the cattle panel mesh is so wide it would be difficult to stand upon.

Add to this the fact that I think that the first coat should be applied all in the same day for uniform strength, and we got problems.

Of course, it will also be a pain in the neck to tie up a dome.
I figure if I do a dome it will have a cattle panel frame, a cloth covering of some sort, ( my wife just happened to buy several big boxes of fabric at a yard sale for her rag rugs and quilts, and amongst it was a big cloth cover for the type of umbrella that goes over one of those round tables folk set outside. I took one look at that and knew it would go over the top of any dome I make! ) and four or five layers of chicken wire over that. No lath on the inside, because that would be such a pain to install.
So the cattle panel frame would not be imbedded into the ferro-cement. I reckon that makes it weaker, but I don't see any easy way around it.
The cattle panel would be covered with the interior gypsum plaster layer.

Covering a dome with chicken wire will also be a pain. I imagine using narrow rolls of wire, and doing the top of the dome first. Then simply rolling bands of chicken wire horizontally around the base of the dome to lock it all in place.
Doing a tubular water tank would be quite easy, because one just wraps the wire tightly around the frame. No odd shapes to try and make the wire conform to.

A barrel vault shouldn't be to difficult to do - But still difficult to tie - Again, we need a lightweight monkey on top to help tie it all up and not distort the chicken wire while doing it. It may be possible to simply stretch the wire over and secure it at both bottom sides, but I doubt it.

I reckon a barrel vault could be made in two foot wide strips - Cut a cattle panel in half lengthwise, and set it up over the structure your roofing with the vault.
Wire it up, and plaster it working from a ladder. Leave a bit of the frame exposed, so when you set up the next two foot wide strip you can connect it, and repeat the operation until it's wide enough. Once dry, you can walk upon it's surface for a final finish coat.

Anyway, these are the best ideas I have come up with to date.
Any ideas certainly are welcome. I'd like to refine this building technique to something simple and straightforward.
I am indeed glad I started with a small project first.
I'll wait till next year before I decide weather or not I'll be doing more ferro-cement stuff. I need to see how this mud hut holds my snow loads.

Ideally, I'd like to build a work shop for myself outta dry stacked concrete block and cordwood, roof it with a ferro-cement barrel vault, and put a layer of sod over it.
We may start on the work shop this year, and just wait to roof it next year. Probably would not get it all done before snow flies anyway.
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#7 EtdBob

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Posted 26 June 2009 - 03:20 PM

Now this is interesting!

http://static.monoli...orm-zweifel.pdf
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#8 purple

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Posted 26 June 2009 - 04:24 PM

Now this is interesting!

http://static.monoli...orm-zweifel.pdf

When we come to visit we will have to place a forklift on yours to see if it holds. :lol: Great find though, We will be using the same system for our underground system if I every get finished with the thousand projects I have going.
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#9 EtdBob

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Posted 03 August 2009 - 01:45 PM

Well, I thought I'd update this post to show the finished tool shed.

Front of the shed. Note the little Harbor Freight solar shed light
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After the first coat to cover the wire, we put two additional coats of cement on the barrel, and one additional coat on the vertical walls.
After an all day rain storm moisture will still seep through in spots and dampen the interior plaster. I reckon I'll paint on a concrete waterproofing compound of one type or another to solve this problem.

Inside the shed.
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Plastering the interior wasn't to bad, except for the fact that the Red Top gypsum plaster I purchased must have been to old and exposed to damp storage conditions. Instead of about an hour working time, I got fifteen minutes to work with each batch before it hardened. So we did small batches.
Plastering up-side-down was interesting. The plaster consistency is rather like a thick frosting. Ever frost an up-side-down cake?
The plaster adhered well, but hardened so fast I couldn't get a very smooth finish. When done plastering, I white washed the interior with lime and water.
The little solar shed light isn't very bright, but because of the angled wall and bright interior it works just fine in this application.

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I'm glad we built this little shed and I think it will last a lifetime, but I do not think I will be building a guest-cabin-dome out of this stuff.
I find that the ferro-cement structure is very hot in hot weather. The thin shell absorbs the heat of the sun and re-radiates it into the interior. It's also cold and damp in cold and damp weather. Not good for a structure to be inhabited. The roof, though strong and fireproof, isn't as waterproof as I'd wish it to be, and the amount of labor needed to construct one is excessive.
I think I'll stick to stucco for walls, and sheet metal for roofs.

Edited by EtdBob, 26 October 2010 - 02:07 PM.

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#10 Indian Girl

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Posted 03 August 2009 - 06:19 PM

Very cool.
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#11 Geo

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Posted 03 August 2009 - 07:06 PM

Cute, quaint door you've got on it, Bob. How many Hobbits live in it?
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#12 purple

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Posted 04 August 2009 - 08:08 AM

I wonder what it would take to make it water proof? Does it condensate bad?
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#13 Tobus

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Posted 04 August 2009 - 04:08 PM

I'm curious about the lawnmower pull-start T-handle in the door frame. What is that for? It doesn't look long enough to act as a latch for the door.

The completed project looks pretty cool, though. I'm partial to lumpy free-form structures. :lol: I'm glad you learned something and shared it with us.

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#14 EtdBob

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Posted 05 August 2009 - 12:38 PM

I'm curious about the lawnmower pull-start T-handle in the door frame. What is that for? It doesn't look long enough to act as a latch for the door.


:lol:
I had a gate latch laying around, one of these things -

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I got it to use on a stall door in the barn, but I wound up using something else in there.
I recently replaced the recoil starter on a little pump I have, so I had this cord and handle laying around...

I put the latch on the inside, because I don't ever want to get locked inside the shed.

I wonder what it would take to make it water proof? Does it condensate bad?

No condensation at all. But during a big rain water will seep through in a few spots and temporarily discolor the white wash.
I don't want water freezing between the layers and separating 'em this winter.

I'll look around for a good concrete waterproofing agent.

Or I'll bite the bullet and add yet another layer of very rich stucco, say one part Portland to one part sand. It's supposed to be water proof. I'm not sure why it isn't.
I used a 1 to 3 mix which seems to be the "standard" for such things.

Cute, quaint door you've got on it, Bob. How many Hobbits live in it?

I reckon it would make an OK bachelor pad for a hobbit...

I feel it is strong enough to earth berm, so it could be used to make a proper Hobbit hole. I'll know more about that after this winters snow load. But the difficulties involved in laying up a barrel vault and plastering it remain, so I don't think I'll be making another.

That's the first door I've ever made. It's simply a plywood panel with rough cut boards glued and nailed to the surface. The door handle is from an old wooden trowel that fell apart during the construction of this shed. :P

I'm partial to lumpy free-form structures

Me too, and they are easy to build. Even my barn, which is a standard pole building, doesn't have a single straight line in it...
:D :rolleyes: :huh:
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#15 Tobus

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Posted 05 August 2009 - 01:13 PM

I put the latch on the inside, because I don't ever want to get locked inside the shed.

Does this come from experience? :lol:

That's actually a pretty smart idea. I'd have never thought of it. And then I'm sure I'd end up getting locked in my own shed, where they would find my bones a few years later with scratch marks on the inside of the door.

That's the first door I've ever made. It's simply a plywood panel with rough cut boards glued and nailed to the surface. The door handle is from an old wooden trowel that fell apart during the construction of this shed.

That's awesome. It's a good way to recycle your old broken tools.

I built a door a couple of months ago, which was the first door I'd ever built too. It was a screen door for the side of my house, using special screen that's supposed to filter the sunlight way down. It turned out pretty darn good if I do say so myself, especially for my first attempt. I just made it out of 1x4's and angle brackets. So far it has stayed square and true.

What I like about your door is that it looks quaint and "homey". It has character. In fact, your whole project has character.

I'm in the process of planning a one-room straw-bale cottage in the woods behind my house, and I really want the door to have the same look as your tool shed door. So I will probably do the same thing: use a piece of plywood to give it a rigid back, and use rough-cut boards on the face. I might even use stripped cedar poles for the door frame like you did. I think that looks wonderful (it's that free-form thing again).

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#16 EtdBob

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Posted 05 August 2009 - 02:33 PM

I'm in the process of planning a one-room straw-bale cottage in the woods behind my house


Oh now that sounds cool!

Heh, you'll be getting in on some of this plastering fun! :lol:

I always wanted to build a small circular straw bale structure, basically one room, with a roof salvaged from an old metal grain bin.

I figured to use a steel cable around the circumference of the structure to stabilize it.
Heck, I bet it could even have a second story.

Put in a brick on sand floor, and with the thick walls the building should stay relatively cool, even in your climate.
I've read of folks who have even insulated the ceiling with straw bales. Talk about insulation!

I might even use stripped cedar poles for the door frame like you did. I think that looks wonderful (it's that free-form thing again).

It's also cheap... :rolleyes:

Sure it takes time to work up timber, but what the heck, instead of spending the time driving yer truck to get lumber, you can spend the time felling, trimming and stripping the bark from a few local trees.
Cedar is good stuff, not the strongest of wood, but it doesn't rot.
Another good place to use native timber is as vigas holding up the ceiling.

Posted Image
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#17 Tobus

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Posted 05 August 2009 - 03:11 PM

I always wanted to build a small circular straw bale structure, basically one room, with a roof salvaged from an old metal grain bin.

I figured to use a steel cable around the circumference of the structure to stabilize it.
Heck, I bet it could even have a second story.

Put in a brick on sand floor, and with the thick walls the building should stay relatively cool, even in your climate.
I've read of folks who have even insulated the ceiling with straw bales. Talk about insulation!

My preliminary design is just a rectangular shaped straw-bale structure, 96 square feet of interior floor space (8'x12'). I considered a round or free-form shape, but perhaps that's something I'd want to tackle after getting basic experience. Not as a starter project. That's really the purpose of doing this: to get some experience working with straw bales. I figure if I keep the design simple and straightforward, it will be a good learning experience that I can't fuck up too badly. :lol:

I'll start by putting down a grade beam foundation made out of rock. Just like I did with my barn. The grade beam will be about 2' wide and about a foot tall. Just enough to get the straw bale walls up off the ground. This part of the project will be slow going. But it will be the cheapest part, since one thing I have plenty of is rock. I'll have rebar dowels sticking out of the grade beam to spike the bales onto.

So basically I'll form a rectangular ring with stone masonry, to act as a footing for the straw bales. Inside this ring, I'll fill it with sand and lay down a brick, stone, or tile floor. Probably with no grout. I want the floor to have an earthen quality to it.

The walls will be load-bearing straw bales in a running bond. No magic here. There will be only a door at the front side of the cottage and a window at the back. Then I'll cap the walls with a plywood/2x4-studded cap, which I will crank down on all-thread that's connected to the foundation. This will pre-load the walls and allow them to settle. Then I'll set the roof framing and finish it off with a metal roof - just a single slope roof, no crown.

Once the walls are stuccoed and plastered, the cottage will be pretty much done. I intend to add a rainwater collection system on it too, just draining into a 55-gallon drum for a rudimentary gravity-fed water supply. I may install a very simple solar system (basically just a small solar panel for a light and/or a fan). But the cottage will be off-grid in every respect. The main source for light, cooking, heating, etc., will be candles, oil lamps, and the like.

I may get fancy and add a front porch with an overhanging roof. It would be pleasant to sit out there in the mornings or evenings.

Aside from trying my hand at straw bale techniques, I also want to see how the structure will behave in terms of its insulation value. Since the cottage will be built in the thick of the woods, it will be shaded from the majority of sunlight and shielded from wind.

I'll have a lot of questions for you, Bob, when I get to it. But of course I have to get through my rainwater collection project first. So this straw bale cottage won't happen until at least this winter at best.

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#18 oblivionboyj

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Posted 05 August 2009 - 03:55 PM

I am having a hard time picturing the way you are talking about doing the foundation, Bob.
Is there a link or could you post pictures on what you are talking about?
The rest of it computes, but I just can't wrap my head around the

grade beam foundation made out of rock

.
Sorry if it should be obvious, but structural engineering is not my strong suit, yet ;)
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#19 EtdBob

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Posted 05 August 2009 - 04:23 PM

Sounds like fun! A mini-cabin, sorta like my next project only different... :D :rolleyes:

I'd be glad to help in any way I can.

Back in 1990 I designed a similar but simpler, even temporary, one room straw bale shack for some friends of mine who had remote property tucked right up on the boarder.

It was mostly for storage, and possibly for use as overnight bearproof quarters. :P
We were gonna use old tiers filled with gravel for a "foundation," and a simple shed roof.
I even hauled 40 bales left over from building my home up to the site, and gave them my bale needles and copy of "Build it with bales".

The couple broke up right after though, so it never got built. Sad.

By the by, there is no need to use all thread, especially on such a small building. It makes stacking the bales such a pain in the butt having to lift every bale to full wall height and sliding it down on a long pin. You can never get the placement quite right that way. You can try coupling nuts and inserting long all thread after the wall is raised, but you'll never hit the coupling nut.
If you cover the exterior with chicken wire, stapling it to the header and an imbedded nailer in the foundation, then stucco it with a Portland / lime / sand mix, you in effect got a thin ferro-cement wall holding the roof on!
Inside, you can do the same only with gypsum plaster.

You can try various strapping methods instead, and probably dispense with the chicken wire. Might be cheaper, given the cost of stucco wire / chicken wire these days. I reckon the stucco will key into the straw well enough, and I know the plaster will.

Anyway, put the roof on first. It's weight is what will make the walls settle. leave it alone for a month, then plaster it.

To help stabilize the walls during building, you'll need temporary corner braces outside, and I recommend using rebar pins and staples in the walls. I had rebar sticking up from the foundation about a foot to imbale the first row of bales.
Starting with the third row, I hammered in two long rebar pins per bale that reached right into the first row.
I inserted pins of the same length in every row thereafter. Pins inserted in the forth row would reach to the second row, and so on.
Since the bales are laid up in a "running bond," putting in two pins per bale really locked everything together.
In the corners I used big rebar "staples" that I'd bent up to help lock the corner bales together.

I was gonna use bamboo pins, but rebar was cheaper at the time! Besides, I'd used bamboo in an in-fill house a year earlier, and everyone got cut to ribbons by that stuff.

After putting up the bond beam on top of the wall, I drilled through it and hammered long wooden dowels right through into the bales below.
The whole construct was pretty wobbly until the weight of the roof went on, but the finished structure is amazingly sound.
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#20 EtdBob

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Posted 05 August 2009 - 04:39 PM

I am having a hard time picturing the way you are talking about doing the foundation,

Look up "grade beam foundation"

It's basically a "beam" of concrete, stone, brick, old tiers filled with gravel or whatever, built on grade.
That means it doesn't go under ground much, unlike standard foundations.

What's under it? Where Tobus is gonna build, he doesn't need much of anything under it.
In my cottage, I have a foot deep trench under the grade beam, filled with gravel.
In the bottom of the trench is a drain pipe to remove any water that accumulates.

Sorta like this -

The building foundation consists of a "rubble" trench filled with gravel rather than urbanite or rubble. A perforated pipe drains any moisture entering the trench and prevents frost heave of a 24" wide by 18" deep concrete grade beam seen below.


Posted Image

This is the concrete grade beam. The building footprint is 24' by 32'. The portion painted black is a waterproofing material to minimize the amount of moisture absorbed by the concrete. We anchor bolted 2x4's to the grade beam with underlayment insulation (pink) to act as a vapor barrier between them. The posts will be attached to the 2X4's


Posted Image

Grade beams are popular with home builders because they are much easier and less expensive to build that "traditional" foundations.
Straw bale builders like 'em especially, because straw walls are so wide. A conventional foundation two feet wide would cost a fortune.

Posted Image
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