June 19, 2016

Weather-Proofing



The photo above shows the final application of elastomeric coating (Maxi-Stretch) to the dome.  The manufacturer (Ames Research) pre-colored the polymer to a light tan shade.

I decided to continue to move away from a traditional lime plaster exterior rendering due to the fact that all the natural builders here in Arivaca have had no long-term success with keeping the lime plaster from separating from a cob base wall.  This is due to the daily 40-50 degF temperature swingshere, that cause lime plaster to expand and contract at a different rate than the underlying cob wall, thus essentially separting itself from the cob wall. 

In the traditional sense, earthen structures need to breathe.  Therefore, I plan to use an earthen rendering for the inside of the dome for that purpose. Here in Arizona, the climate is mostly very low humidity, therefore excessive moisture in not an issue compared to other regions. 


The coating in the photo above was the intermediate coating of liquid rubber.  The trade name is Blue Max.    It's really cool to paint-on your own rubber roof.  Note that Blue Max is not UV stabilized and requires a top coat of elastomeric such as the applied Maxi-Stretch


I took this photo knowing I would need to show the layers of applied coating to descibe the waterproofing concept for the dome.  In the photo above to the right, two applications of Super Primer by Ames Research, which acts as a sticky base coat which hopefully will securely adhere to the straw/clay mix and provide a base surface to build-up the other coating.

Then again as discussed above, I applied to coats of liguid rubber (Blue Max), followed by 3-coats of elastomeric.   This brings the weather-proofing to seven total coats for the dome.

Please note that this process of appling a painted-on rubber coating onto cob (straw/clay) is EXPERIMENTAL, with the thinking that it cannot be any more of a maintenance burden that having to replace a lime plaster rendering every two years as has been the case with other adobe building I have constructed.

Also note that these high-tech coating are non-toxic and safe for water-harvesting.

May 31, 2016

Dome Fully "Cobbed"


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 Nothing like a completed dome!



The photo above shows the inside of the dome looking up from the scaffolding platform inside the circular room, upon which the dome was built.

The photo tends to 'flatten-out' the dome shape.  Working that last top portion was tiring for my arms reaching up to shape the drying cob.  

May 23, 2016

Bamboo Supporting Strips Added


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As mentioned in the previous post, as reaching the top of the dome nears, I needed to add strips of bamboo inbetween the rebar support (see photos above).  At this point, I simply grabbed as much cob as I could and placed it on top of the bamboo strips and rebar then shaped accordance with the evoliving shape of the dome.

In the top photo, I'm working from the inside.  If you look closely, especially to the left of me, you can see how the cob has slumped and fallen in on itself somewhat.  I just have to removed the excess and place where it's needed and just keep working it until the inside surface is shaped uniformly.  

May 12, 2016

Closing In


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I'm at the point in shaping the dome where the angle inward begins to get pronounced, therefore, I'm making my 'cob' mix stiff so it doesn't slump too much and fall in on itself. 

At this point I have had to raise the scaffolding so I can comfortably reach as I move around the dome to work.

April 18, 2016

Scaffolding Necessary to Complete Dome


I took a day to arrange the scaffolding in order to work comfortable at the top of the dome.  The photo may suggest a precarious situation, but actually the platforms are stable.


The dome has changed everything with respect to the architecture and imagination of the structure.   And the inside ceiling of the dome will open possibilities for finishing renders and lighting.   I hope to complete the dome before the summer monsoon season around the beginning of July.

January 18, 2016

Dome Progress Update



Work on the dome has finally resumed after a failed well-pump needed a few months to order and install.   As the dome rises and the cob needs to be hauled up scaffolding, progress takes longer, but the winter days here in southern Arizona are beautiful - sunny in the low 60's - perfect weather for cobbing.

I'm using the rebar skeleton as a guide to shape the exterior of the dome. It's all by eyeball. The thickness of the dome wall is approximately 1-foot thick.  When shaping the dome, I parallel the rebar.  But as I near the top and the angle change is more pronounced and the challenge to shape the dome uniformly increases.



December 15, 2015

View of South Side



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With winter here and leaves off the trees, a photograph of the south side of the studio can be taken.  Progress on the dome (top-left) has stalled due to a problem with the well pump; but hopefully it will be resolved soon!
 

September 13, 2015

Dome - Mid September 2015


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I took a moment to photograph the dome as the late summer's monsoon season continues to resurrect itself  into September. I took these images for a status update on the dome: But now that I look at them I noticed the light and an approaching storm in the sky

July 28, 2015

Bond Beam & Dome Progress


A section of bond beam was poured (see photos below) on the wall supporting the east side of the dome.  This was a necessary step since the size/shape of the dome on the east side extended slightly onto the bond beam (photo below)

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As can be seen in the photo above, the 12-14" thick 'cob'(clay/straw) walls of the dome provide incredible strength.  As the dome rise the walls will be made thinner and with more straw to reduce weight.


The photo above shows the freshly poured bond beam on the east side of the dome.

July 12, 2015

Cob Dome - July Update



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The 2-inches of rain so far kicking off the monsoon season here in southern Arizona has barely put a scratch on the progress of the cob dome.  Work makes slow progress in the summer due to unpredictable thunder-showers, heat, mosquitoes and mud.  

The photo above shows preparation for a 'bond-beam' pour for the wall making up the room to the east of the dome (not shown).  The photo shows the rebar in the trench where the concrete beam will be poured.  Note the 'form-in-the-sky' shown to the left in the photo, has a strip of flexible 'Masonite' board as the left side of the trench.  The Masonite is held in place by wood - short 1"x2" (wood stakes) and 4"-deck screws.  The cob holds these long course-threaded screw really tight.  So much so that it's going to be retaining the concrete as it's poured in the form.

Once the bond-beam is poured.  I'll be able to use it as a working platform for the east side of the dome construction.  

Just a note that the thickness of the wall on the left side of the photo between the main room and the dome is a massive 3-feet (lots of cob!).

May 17, 2015

Dome Rising


Took advantage of temperatures dropping to 70-degF to work the dome.  With the assistance of Nick Dunn whose currently over at Forever Yong Farm in Moyza; we hauled over 1,000 pounds of cob up scaffolding on Sunday, to add another layer.

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Photo above showing the dome's outlined shape - structured with rebar. 

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Close-up detail of sculpted cob rising off a concrete bond-beam base, curving in parallel with the dome-shaped rebar.
 
 

January 25, 2015

Next Step - The Dome


I took this photo after thinking about the 'dome building' phase of the project which I plan to work next.  The dome is a shape that's captured my imagination in studying Middle Eastern and early cultures.

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January 22, 2015

Exterior Render


I have been amazed at the resiliency of cob to hold-up in the rain.  In Arivaca, the rainfall totals on average per year are about 15-inches.  This past year (2014) we had over 20-inches.  Some of the walls of this studio have been exposed to the elements for 5-years and the photo below shows a typical section of exposed wall.  

 
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The downfall with the traditional lime-plaster here in Arivaca where temperatures fluctuate more than 40-50 degF a day, is that it eventually separates from the wall due to differing rates of thermal expansion between the plaster and cob wall.  And thus every couple of years the entire building requires new application of lime plaster.   

So I'm developing an experimental method, I hope will be over time will require only light maintenance. 

The photo below shows a thin layer of cob (clay/straw/water) mixed with colored elastomeric, that I have been experimenting with as an alternative to lime plaster.  I'm hoping the exposed straw from the eroded wall will help grab and hold this thin exterior cob (clay/straw) render.  This approach is a mind-set change from the traditional lime-plaster render, that although breathable, provides a uniform 'seal' to cob/adobe buildings.  


Last summer I applied a test coat of this mix on parts of the south wall to see how it would hold-up during the summer monsoon season.  The photo below shows how the cob render with added elastomeric (about 1-quarts per 1/2 wheel-barrow of cob), did exhibit some erosion; but I don't think I put enough elastomeric in the summer test mix.   So going forward, I'm adding 2-quarts of elastomeric to the 1/2-wheel barrow of cob.


The photo below shows most of the east side of the building rendered, with the just a quarter of the building on the right side still needing to be completed.


The photo below shows the remainder of the east side of the studio with the completed render.


July 03, 2014

The Pour-In-Place Roof


The completed fully water-proofed elastomeric protected earthen roof for the north room after seven coats of elastomeric/rubber/acrylic formulations.  This approach was experimental, but when completed the result exceeded my expectations.  This roof should be extremely durability and easily maintainable.

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The photo below shows a close-up of the elastomeric roof after three painted-on coats of AMES Research Maxi-Stretch. The surface looks a little rough, but that's due to the roof's clay/straw material make-up.


Close-up of drain receptacle with final coat of elastomeric (below).


The photo below show the earthen roof after three coats of Ames Research's BlueMAX Liquid Rubber.  The coats of this liquid rubber followed the application of Ames Research Super-Primer.


The first challenge of building a rubberized membrane on top of a clay/straw roof was establishing an initial coat to attempt to adhere to a clay/straw substrate.  This was accomplished with the use of Ames Research's 'Super Primer' which is a penetrating pure acrylic elastomeric plastic sealant.

Earthen (clay/straw) roof ready for the first coat of acrylic elastomeric sealant



The picture below shows the Super Primer acrylic as applied to the clay/straw roof.


A close-up of the dried Super Primer.  You can see the straw that's fixed in the clay and also adhered to the Super Primer.  Despite this whole process being experimental on my part; after this first primer coat, I had confidence the idea of building my own rubber/elastomeric roof from scratch would be a robust waterproofing solution. 


July 02, 2014

Forming the Parapet Wall Top-Cap

After the pour of the concrete top-cap, the inner forms were removed and a final layer of cob (clay/straw) was applied to the earthen roof to establish a contour to ensure rainwater would be directed to the drain.

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A hang-over "Lip" was established for the top-cap on the parapet wall during setting-up of the forms by placing strips of 3/4" foam-board on either side of the wall. 


The photo below shows the strips of flexible Masonite board 2" over the top of the parapet wall forming the top-cap.  The Masonite is holding the foam-board in place and itself if fastened by 4"-deck screws that secure into the cob wall - solid.


The photo below shows the completed form all-around including reinforement bar.


Below, a close-up of the south side of the north wall where the thickness has increased to 4" thus transitioning to a bond beam for large main room of the studio.


The south side of the north wall all has metal straps that will be used to secure the vigas (beams) that will eventually support the roof of the main room.


View of the north side wall of the north room.  The use of the Masonite to create curved forms was a real innovation for this curvey structure when pouring bond beams and top-caps.


June 17, 2014

North Roof - Parapet Wall & Drain


Work on the north room roof continued with the of building a parapet wall around the perimeter of the earthen roof. Providing for a drain from the north room roof across to the south where the natural pitch would move the water away from the building.

About 14-ft of 3"-dia ABS pipe was required to establish a drain-path along the wall separating the large main room from the circular dome room.  I had to design the drain inside the wall in order to efficiently move the water from this north roof to the south side of the building to take advantage of the natural grade of the land which slopes to the south.  I had to use a pick to curve-out a channel in the cob of the existing wall.  It's incredible how hard a basic clay/straw mix can be. It took several hours to carve a simple trench to accommodate the pipe.


In the photo below A 90-deg elbow and drain collector was attached to the north end of the pipe in order to act as the collection point for the north roof.


A found an old plastic battery enclosure in my resource area (aka 'the junk pile') to use as framework for a mold for the drain box in the parapet wall. The photo below shows enclosure on top of the drain and the cob wall built-up around the box to act as the outer form of the mold.


The string-line shown in the photo will be the finished height of the parapet wall.  The final height was established using a surveyor's level to ensure height uniformity.  The photo below shows concrete poured in the mold to create the drain box and some concrete to establish a solid collection area for the drain.


The photo below shows the formed concrete drain-box with the plastic battery-box framework removed. At the entrance of the drain collection area, a concrete floor area was added as robustness, for water that will drain into the box from this specific north roof.  


Finally, an overall of the north roof, showing the finished cob parapet wall, earthen roof and drain area at lower-left of photo below. 



I found a section of fired-clay pipe at a salvage yard and it sliped over the 3-inch ABS pipe.  Even though cob (clay/straw mix) would cover the pipe as the walls continue to rise, you can see in the photo I bent into a "U" shape a piece of rebar and pounded it down into the cob wall to secure the clay pipe in place.


The clay pipe shown below extending a couple of feet out from the south side of the building.  The cob wall is now shown built-up above the pipe.



Note: The next steps will be to pour a concrete top-cap and waterproof the earthen roof with a rubber membrane.  Those steps will be posted next as completed.

April 21, 2014

Overview and North Roof


A southeast view of the studio showing some recent 'cobbing' around where the dome will take shape (right-side).  And the North roof parapet wall of cob freshly built-up (dark clay-left side).

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Photo below: Shaping cob on top of the north wall, beginning the formation of the parapet wall. 


This roof construction will continue so keep tuned for future updates.

March 31, 2014

North Room Roof In Progress

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The above photo shows the current progress on the building, in particular the North room roof which now is covered in 5-inches of "cob" mixed with less clay and more straw to make it lighter. 


This roof will require the addition of a parapet wall , proper water-proofing and drainage that will be discussed in future posts.