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.


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.  


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.


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.


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).


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


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.

February 15, 2014

North Side Roof Line

The room on the north side of the studio will be for the solar power electrical equipment and the battery bank.  The room will eventually be separated by a wall with the other half for storage.  Since this space is essentially a utility area, I decided to make the ceiling corrugated metal for cost and ease of assembly.  You can special order heavy-gauge corrugated metal sheets from a building supply store. 


I like mixing-up the materials in this building.  The metal is not ancient Anasazi architecture for sure, but I was unable to locate the aged wood planks I originally wanted.  This building is not about "intention" in design anyway.  Rather the point is rather that the building is becoming its own eclectic style from the decisions made for various reasons along the way.


The photo below shows about 5-inches of cob in a lighter mix (mostly straw to reduce the weight), that will be part of the evolving roof structure you will see posted in the coming weeks.


January 30, 2014

Time Has its Own Pace

The Photo below of the studio was taken standing southeast, looking Northwest.  Friend and fellow filmmaker Scott Griessel of Creatisa stopped by with his wife Anna for the afternoon and we took some creative time to snap a few photos.  

if you want to see some nice artistic shots of the studio that Scott took on his visit, click on the following link to my "Outpost" blog on Tumblr.  


The photo below was taken looking up at a portion of the southeast room as seen in the photo above, protruding-out.  Notice the band of concrete making up the room's 'bond beam' at ceiling wall height. I plan to finish that exposed concrete with a tile of yet unknown design. 

The drain pipe was recycled from a construction dumpster. Then at the top notice the thin band (2"-thick) of colored concrete as a top-cap to the parapet wall. The top-cap will eliminate the need for re-patching lime plaster in the future (lessons-learned from my adobe outbuilding project). In addition, it will assist future roof maintenance in the future by being able to walk-along and place tools on the top-cap with worry of damage to the wall.

September 23, 2013

North Room Roof Underway

The North side will serve two purposes once the studio is completed.  The room will be divided in two with one half being the battery and electrical room for the solar photovoltaic power; and the other half of the room will be storage for equipment.


I used 6'-Ponderossa Pine vigas to span the narrow width of this 4'-wide room, set roughing 1'-10" apart.  The vigas are 8"-diameter.  As shown in these photos, I then 'cobbed' to the height of the vigas in preparation for the roof decking.

As can be seen in the photo above, the landscape has 'greened-up' from the summer rains.  A protective covering of tar paper was placed on top of the walls for protection from the rains. Now that the fall is approaching, rainfall will be minimal for several months and along with the temperature drop, it will be a good time to work.


(Photos above) A view looking-up from inside of the North room just after the vigas were placed and secured using metal straps imbedded in the concrete bond beam.

August 19, 2013

Concrete Pour-Off for Dome

The base cob wall for the west circular room will support the dome structure.  Since the supporting wall is 2-feet thick, compared to the dome structure that will be between 12-14" thick, I needed to consider rain run-off as part of the design.  The cross-section drawing below shows a triangular-shaped concrete pad (aka concrete pour-off) at the base of the dome that will allow water flow down the dome and off the wall.  This will insure the long-term durability of the wall with minimum future maintenance.


The photo below shows how the 'pour-off" was formed using the same Masonite strips anchored with 4"-deck screws and 1"x 2" wood strips (other examples can be found in this blog).  The Masonite form extends 2" up from the top of the outer cob wall. The other side is 5" in height formed by using cob.  1/2"-diameter rebar in the trench, anchored by vertical rebar in the base wall can be seen in the photo (and the illustration above).


The next photo shows the trench poured with concrete.  I added a brown concrete coloring to tone-down the typical concrete color look.

This next photo shows the completed work which covers about half the circumference of the circular base wall.  The reason why the the pour-off doesn't go all the way around has to do with how the roofs for the remaining two rooms are to be built and will be covered later.  Note: The black tar paper shown on the left, held down by tile fragments is temporary to protect the top of the wall from the summer monsoon rains.

The final picture is an overview of the west side of the building looking east.

June 07, 2013

Cob Roof Fabrication - Narrated Slideshow

There was so much information on the cob roof, that I created this 10-minute narrated video slideshow that details construction of the cob roof for the southeast room.  It's meant to provide information to you 'cobbers' as opposed to entertainment, so bare with it if it seems a little dry.  PLEASE CLICK LINK BELOW


April 29, 2013

Cob Roof - South Room Progress

I plan to post a more detailed account the roof assembly once I decide on the water-proofing membrane and complete the work. In the meantime, I am providing this status photo to document where am at this moment.

The photo shows that the roof has been covered with a layer of cob. However; note that for this (roof) mix I used significantly less clay...so that after the water evaporates from the mix, the cob will be lighter.  The light mix mitigates weight as an issue for the supporting roof beams (Vigas).

The photo also shows that the surrounding parapet walls are taking shape but are still about a 12-inches from their final height.  I use my regular (heavier) cob mix for the parapet walls.


Also, additional cob will need to be added to the roof to provide sufficient slope and contour to allow the water to flow out the drain pipe at the SE corner of the roof.

Here is recap of the built-up roof material used to date: 1) Ponderosa Pine beams (vigas).  2) Bamboo latillas.  3) burlap on top of the bamboo.  4) 2"-Rigid foam insulation.  5) 6-Mil plastic.   6) Light clay/straw cob mix.

April 15, 2013

Mesquite Base for Mounting Speakers

Speaker wire was run through the cob as the walls were being built (see earlier post HERE).  Using a surveyor's level, I marked 10-ft wall height at four locations on rebar equally spaced around the large oval room.

I cut a log of mesquite wood into four pieces and drilled a hole through the center of each piece so the wire can extend out.  But the main reason for using the mesquite is that the wood will provide a strong anchor for the large 1978-vintage Genesis I Physics Speakers that I had restored to provide an analogue warmth to music and other audio to this earthen room.


March 26, 2013

Bamboo Ceiling for South Room

A bamboo ceiling was created for the south room (below) using the two large vigas shown in the bottom photo to support the bamboo poles across the span.  The term used historically and today in the natural building community for this cross support is "latilla".


The bamboo poles were precut to length and holes drilled at the proper spacing between the vigas to help speed the installation once on the roof.  The bamboo poles were secured into the vigas by 4"-exterior deck screws and 1"-washers.  The washers helped spread the clamping force of the screw on the bamboo; and the pre-drilled holes helped prevent cracking and splitting of the dry bamboo.

When the bamboo poles were laid-down, careful attention was paid to select a pole whose orientation would provide a 'crown' for better load distribution and in addition; each pole was selected to best match the pole laid-down before it so the gaps between poles would be minimized.

Preparation of the bamboo involved cleaning the poles with an abrasive sponge soaked with a mixture of water, bleach and a mild cleaning powder.  The mix of cleaners was necessary because the poles were under tarps for several years and showed signs of mold. 
Another major issue was evidenced in some bamboo holes by tiny holes that meant 'powderpost-beatles' were present.  Over time an infestation of these tiny mite-like bugs, can turn these poles into powder.  In order to ensure the beatles would not (further) harm the good bamboo poles, they were all treated with an insecticide, then wrapped in plastic overnight.  Note that 'Borax' will kill these beatles but I was unable to locate borax in time, so I went with the insecticide.
Finally the poles were coated with a wood perservative and waterproofing sealer that helped bring out the grain and color characteristics of each pole (see above photo).
The vigas and latillas are just the start of the roof structure.  In the coming weeks, this blog will detail the buildup of the roof from this point forward.