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Sharing my little cobwood studio project-in-progress  RSS feed

 
Mary Love
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Hey Permies folks!

It's raining here today in Mi's Upper Peninsula, which has briefly paused production on my project, thus giving me a window of opportunity to share what I'm working on with everybody.

First, let me just explain that I'm a kid (well, 24, so piratically but not technically) so in the realm of natural building I'm a wee bit intimidated to be sharing amongst the experts here, but I also wonder if my project (and youth ) will inspire those non experts like me, so I'm sharing. (Maybe I'll be back in a year to delete this post if my place falls down, haha!)

I've an older brother who is experienced in carpentry and building, and my family and I have tackled two natural buildings in the method I'm using, so I'm not completely without skill or help and I'll admit that these two things gave me the gumption to attempt this project. I bet a lot of you have seen my family's current cobwood house pictures floating around on the internet, and possibly our little cobwood barn as well.

Anyway, I got full of inspiration--knew I wanted it round and curvy--picked a building site on the wooded ravine edge of my parents garden, and went out there with a shovel to start digging out tree stumps in Aug of 2012.




That winter I trekked out to the site in 4 feet of snow every few days to chart the path of the winter sun, picking my window placements and trees that I wanted to remove for more wintertime sunlight. I designed my little studio, researching the unfamiliar techniques (such as a reciprocal frame roof) and flushing out my blue prints with a scale model made out of (what else?) cob. It's not perfectly to scale and actually hasn't proven useful in any way, but it was fun to make, and the winter's are long up here (yeah, I was just bored and excited!)

I carved an imitation of my site's ravine edge into some foam insulation and copied my blueprints onto them for the base of my model. I also included the little interior 'step' that separates the levels of my studio, following the lay of the land.

I used bits of plastic for the windows, most of which I ended up moving around since scavenging windows and spending more time out at my building site.

This project did little for me other than increase my love and admiration of cob and excitement for the project! Well, and produce an impressively strong dollhouse made of mud.


Playing around with sticks and wowing myself at the ingenuity of the reciprocal frame design (whoever came up with that is freaking amazing!)


The next spring did not come early, (as usual for UP here) so I shoveled the drifted snow banks out of my site in my impatience to get the land drying out so I could get my shovel back out and resume digging!


Like the model, my blueprints were all but discarded when I actually started digging. Mostly because I was on a bit of a nature high, spending that much time by myself in the woods, and it was more important for me to give my favorite ash tree another two feet of space than to stick to my original 20' diameter circle idea. And, as I would come around the various corners, I would be inspired to move around as the soil and landscape directed my shovel. Not too drastically, (I had to keep my roof in mind) just a lot more than someone with a backhoe and dogmatic blueprints would be able to. When it was all said and done, I guesstimated the place to be just over 400 round feet.



Our frost line is 4 ridiculous feet, but since I was finding my soil less clay-y and more silty/sandy (perks of adjusting the layout to follow the easier-to-shovel areas I guess ) and it's also on a ravine edge where water never lingers long, I decided to go 3-3.5' and call it gooda'nuff. I dug a runoff trench at the lowest point and tamped the whole thing to slope there. (The clay looks wet in the above picture because I was throwing buckets of water in to make sure they ran out.)

Wrapped some drain tile and gravel in landscape fabric to keep out the silt, tamped, threw some more gravel in and tamped, tamped, tamped. (My brother's homemade water level tipped over into the trench--another ingenious invention!)

Note my family home in the background, but do not note the farm clutter behind the shed!!




I'm going to share in increments to help keep the pictures (and my brain) organized. I'll be back with my earth bag foundation pictures in a bit!
 
Mary Love
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I chose earth bags for my foundation after we used them as the stem wall on our barn project. I liked that they worked up fast, were small enough for one person to do (yet extremely solid once tamped) and I imagined them working well and being pretty adjusting to my curvy foundation trench. (Spoiler: I was right. )

My brother helped me get started on the first few bags, then I was on my own for the summer!


For the first few layers of bags (until we were at ground level) I used a road grade gravel mix. It was a lot cheaper than the washed stone, tamped well, but still enough gravel to drain water (I think, haha). Once we were at the grade, I started mixing clay back into it, which extended the mix and tamped out even harder.


I slowly worked the bags up the sides of my grade, adding more gravel between layers as I climbed back up. I stuck green treated supports amongst the bags, planning ahead for my future back porch.

The water level continued to be a great help, keeping both sides level to each other until I made it all the way around.

On my own, I averaged a meager 12 bags or so a day, but I still finished after a few months.

Free-flowing and curvy!

This is before I bermed the earth back against the wall, which brought the inside level up for a better view of the ravine.


I got more brotherly help insulating the foundation. We used two layers of 1" foam so that it wrapped to the bends better. We tied the insulation against to the foundation with strings that I had been attaching to the barbed wire (between the earth bag layers) as I went along (thinking ahead there!). We poked hooks through the insulation to pull the strings through and then tied them to scrap nails, pulling the insulation up against the bags.

I then attached a netting (like chicken wire but cheaper) to the foundation and plastered it with two layers of cement.

This is the scratch coat, the second one my sister kindly troweled beautifully.







 
Mary Love
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Late in the fall of 2013, I quick pulled my earth bag tools back out and made a few little retaining walls inside the foundation, distinguishing my two interior levels.

I elbowed this one back into the upper level, acting as a mini buttress to help strengthen it.

If you look closely, you can see that I also very subtly angled the wall towards the grade and also gave it a bit of a bend, both with the intention of aiding in it's overall strength.

I was proud to have built this wall in only a few days... everything takes longer than you'd expect when it comes to building... Thankfully, I'm in a comfortable position in my life that allows me to build at my own pace, spurred on more by my own impatience than anything else!


On the kitchen side I threw in a quick experimental root cellar of sorts, made of earth bags. I say 'threw in' but since I had already put some ventilation pipes in that area of the foundation, it wasn't as though the box was a last minute decision.

The root cellar box is in progress in these pictures. Since I'm not there yet, I still don't know how it will work (I stuck in a few leftover pieces of insulation where the eventual rocket stove heat source will be a few feet away, hopefully blocking any heat from leaching through the earth bags).


Once again, my plans were only referenced vaguely in the back of my mind as I built. These walls were game changers to the interior design that I just had to go with. You try to plan ahead as much as possible, but as some point you just do it, even when it's different than you'd originally planned.... since I'm not living there yet, I'm still hoping there aren't too many regrets.

This is how the foundation/site was looking spring of 2014:

My yet-to-be-achieved plans include a rocket stove bench against this wall, separating the two interior levels.





Tarps covered the tops of my earth bags, shielding them from unnecessary exposure to sunlight over the winter.
 
Mary Love
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I got a load of red pine logs dropped off for my rafters, which some cute siblings helped me peel.

Unfortunately it was late summer before I started putting posts up. My brother had a busy summer.

After he gave me a few tips, a strong younger brother helped me put up the rest.

We used the popal trees we had taken down to clear the sight, so they were now two years dry.

Since this 'timber frame' was all going to be buried in the walls, we weren't too concerned with aesthetics of it.
Other than standing them up on green treated pads (to spread the weight out on the bags) and a few big nails sticking them to the bags, they were only being held up with braces.

So I breathed a little easier when my older brother was available to help me put the top beams on, tying everything together.

After that I was on my own again to drill and pound 12" rebar spikes down into the top of the posts.

I discovered two things while doing this: 1) Two year dry poplar is haaaard.

2) I don't like heights and had to wonder at the tall design of my ceiling!


Then, on a cold rainy day in fall of 2014, I dragged my brother out there to help me (okay fine, I was helping him!) put up the rafters in the reciprocal frame design.

The rafters were surprisingly light, as the two of us were able to mange this task without help.

We got them up in a day, just tying as we went along and then spiking rebar and 6" nails around the top.

When the last rafter came up a little shy of it's neighbor, we had the idea to ratchet them together before dropping the charlie stick.



It was a momentous day for sure...



This spring I went around and pounded yet more rebar through the ends of the rafters and into the even harder (seeming) lengthwise grain of the poplar beams.
 
Mary Love
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This spring I ran around gathering more building supplies, including the 45 mil (pond liner) plastic membrane and some foam insulation for the roof. I was bummed when the lumber I ordered to sheath the roof took a lot longer than I had anticipated to arrive (the trouble with local neighbor sawmills) so instead of starting with the roof as I had hoped, I decided to (finally!!!) start cobbing!

The first two batches of cob went on May 7th.

The road restrictions preventing a load of sand from being delivered (for making cob) didn't stop us. We were hauling sand up from our creek beds for the first two weeks (not gonna lie--that killed!)
My Mom stomping the first batch of cob in a pit I prepared on the ravine edge below the house site (so we didn't have to haul the sand as far).

Insulating with sawdust/lime mixture.

The previous winter I spent a lot of time cutting and taping bottles together for sticking in the wall and letting in natural light.

Since the logs primary goal is holding the two (interior and exterior) cob walls together, I'm crisscrossing the longs at soft angles, especially around the posts.

The method we're going after is quick and dirty and then, after a season to dry, I'll come back and completely plaster over the interior and exterior.

This is the first two batches.

One of the cons to walls before roof is a lot of tarp covering at any chance of rain.


Getting the sand dropped off really sped up production, but I almost wondered if it was due more to my putsy tendency to wander the creek day dreaming instead of hauling sand than the convince of a closer sand source.
Their home, my home:


I got my cedar porch posts sunk with the help of strong determined siblings chopping through tree roots for me.

I needed them sooner than I realized to access the back wall. I've since thrown some trusses and temporary sheathing so we can safely use ladders around the back.

As we make our way around, it's like I'm seeing the curves of my foundation for the first time all over again.

Yay for curvy walls.

After the initial excitement wore off, it's pretty much settled into the routine of me and this sister working. She's faster and better at cobbing than I am, and I'm so grateful for her.

When the weather is good, we can easily manage about 6 batches. A batch takes maybe a little under an hour, not counting splitting wood, mixing sawdust, chopping straw, soaking clay and so on.
 
Patrick Mann
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Very cool - simple but effective design; looks great too. I was wondering what the blocks in the outer wall were for until you posted the deck pictures.

How do you work the sawdust? It looks like you are sandwiching sawdust between cob?
 
Mary Love
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Patrick Mann wrote:
How do you work the sawdust? It looks like you are sandwiching sawdust between cob?


Indeed. We're mixing in a bit of lime to deter critters and sticking it in there as insulation. It's a necessary block in our climate; a solid cob wall would likely wick the cold right through. I recently saw a cobwood home built the same way I'm doing, (plastering over the log ends inside and out) but they opted to just leave an empty air space in the wall there for an insulation break.
 
Mary Love
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We were ready for our first window frames after just a week or so of two girls cobbing. (bragging rights? )



Note the back door on the far right, leading out to the back porch.

The morning of a work day.

This is also as far as we got before the sand was delivered, so everything you see on the wall was mixed with sand hauled up the ravine from our creek bed. The clay is also right next to the site, leftover from when my family dug a root cellar a few years past. It's nice to have the building materials gleaned from right around you, BUT, that being said, I had no complaints when the sand was finally delivered!

The evening of that same work day. Note the increased height on the window frames.



These pics are from May 21st. Since then, we've only had a few good work days, juggling them between rainy weather. The other night, my sister and I were down-poured on by a stray thunderstorm mid cobbing. It made our freshest layer of cob a bit soupy, as we rushed to finish and cover up, but I wasn't real concerned. Cob is very forgiving, I've learned.

Small helper in the cob pit. Small, but seriously helpful!

View from my family's garden. When the sod roof is on and growing, I hope it looks just like an extension of the land!

The goal is to finish cobbing in Aug and start on the roof, weather and bugs permitting. I'm not at all rushed though, so it's a variable goal. I'm not even aiming to be in by winter, since the rocket stove and earthen floor will be big projects as well, and I'm okay with that. Anxious as I am, now that it's spring and everything's finally coming together, these beautiful cobbing days have been among the most peaceful and happiest of my life, so I don't really want them to pass too quickly.

That's all for now, I'll continue to update here as landmarks are made.
 
Mary Love
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I apologize for the photo intensive post, particularly the duplicate photo postings in the rafter post from last night which I apparently can no longer edit to remove (admin?).
 
Mary Love
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Update:



Bottle art in the walls.



Plastic and gravel in the floor.



Here's where we're at the the beginning of Oct.







Still planning on finishing the sod roof (man that sheathing job takes time!) and buttoning her up better before the snow flies.

 
Wade Glass
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It looks amazing!

You and your family are very talented
 
Mary Love
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After a few very challenging weeks, I finally got my roof insulated with foam and covered with pond liners. I still have to stitch them together to make it perfectly water tight.





I put down white paper first, just for aesthetics so you don't see the foam through the gaps on the ceiling.



The gaps made the roofer lighter (sod will eventually go on the pond liners and be quite heavy) and, obviously, cheaper.





This is where I'm going to leave off this project for the winter. Next year I will plaster completely over the walls, inside and out, build a rocket stove and lay my floor. I hope to move in next fall.




 
Daniel Ray
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That is some gorgeous building! Awesome job. I was wondering what the span of your reciprocal roof was? Are you planning on plastering with natural clay plasters or are you going to add lime to the mixture? That is going to be one beautiful home.
 
Mary Love
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Daniel Ray wrote:That is some gorgeous building! Awesome job. I was wondering what the span of your reciprocal roof was? Are you planning on plastering with natural clay plasters or are you going to add lime to the mixture? That is going to be one beautiful home.


Thanks Daniel! The roof span varies since my foundation is all over the place. It's closest to being 20' diameter, give or take a few feet as it goes around. Natural plasters on the inside. I was considering using lime on the outside, but we've plastered over a portion of our cobwood home (outside) without lime and it's holding up really well so now I'm more open to the idea of doing natural clay outside as well. I'll keep an eye on it over the winter and see how the snow treats it before I decide.

 
Daniel Ray
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You shouldn't have many problems with the natural plaster outside. I used natural plasters on my cob home with just a bit of linseed oil mixed in and it hasn't had any problems.
 
Terry Ruth
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First, let me just explain that I'm a kid (well, 24, so piratically but not technically) so in the realm of natural building I'm a wee bit intimidated to be sharing amongst the experts here, but I also wonder if my project (and youth ) will inspire those non experts like me, so I'm sharing. (Maybe I'll be back in a year to delete this post if my place falls down, haha!)


No worries, I dd not read the entire thread just looked at photos. The Styrofoam DOW does not rate it for ground contact so it has a perm rating of zero meaning it will not "breathe" meaning where it contacts soil depending on it's composition it will more than likely become a microbial food source especially if your climate sees alot of heat and moisture or cold condensation, and it's compression strength and deflection before it cracks over time is low if you get alot of snow and wind driven rain and/or your building has a lot of flex or deflection which it appears to not have a PE stamp of approval. Once the foam cracks or vapor barriers such as house wraps or plastic sheets tear, which in most cases will happen, now things just got a whole lot worse! There is nothing "natural" about any foam and/or man made plastic products acting as barriers to vapor release. Soils are greatly misunderstood and can be a fungi and bacteria food source if not processed properly.

Mineral wool IS a little more expensive would be a better choice it @ 1.5-3" inch thick has an effective "real" when wet r-value of 6, double stacked and staggered more like 10-12 or up to 25 and has a super high perm rating 25+ which may not be enough to stop the thermal bridging of the soil and wood in both the walls and roof. There is no real data on any of that since there are too many design variables but, if your walls surfaces feel cold and condense or feel wet and cold then you know you are loosing heat and or cooling, and fungi is producing in the outsulation layer which can leach through the walls and cause medical issues it is proven. Chances of success better with mineral wool rigid board than foam. I doubt you ever get to net zero utility bills without any mechanical devices for heating and cooling with this design unless in a very mild climate zone with day and evening temp and moisture swings stable 72 f and 40% relative humidity. In the future anyone trying this with foam install a ventilation gap between it and soil/foam with wood furring or contact me.

How well soil renders do when exposed to nature and the elements depends on the type or soil/wood/foam and climate, there is no general rule and just because one succeeds in a climate does not mean they all will. I'd suggest siloxane or silane (sand or natural silicone types) sealer with 40+ solids over linseed or any low perm rated oils on soils that will not allow the wall to breathe nor last the test of time and dry out but, siloxane will stop liquid water from getting it and allow the wall to breathe well. If you look at my thread called "breathable Walls" lineseed oil on most soils fails the lab test. Other great thing about mineral wool rigid board IS like Roxul designed right with sealed properly processed earth is it also drain board and is a chemically inert composite assemble.

If you have enough soil thickness outside that foam for the soil to manage the vapor pressures then it may never reach the foam layer, that is a big IF. Same for the roof.

There is more as far as how sustainable this design is but I'll stop there ..I'm always available for a price for consultations and I do natural building 3D modeling, renderings that look totally real before you build, and drawings which can be hard to find. My contact info is below.
 
Bryant RedHawk
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hau Mary Love, what a wonderful and complete building project post. I am sure it will help many others that have aspirations of building a sweet, curvy building.

phila'waye (many thanks) to you for sharing such a wonderful adventure in construction.

Redhawk
 
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