Natural Walls - The Remix Edition

Time for a barn-raising!  The last two insulated wall systems for our barn are straw-bale walls.  The bales are stacked in a running bond, secured to our frame with strapping and stakes, and whatever holes and cracks are created between bales are stuffed with light straw clay knot to make these walls as tight as possible.

You can see the black strapping securing the corner bales to the timber frame and exterior framework.  Corners are notorious for blow-out, so this detail is especially important.

Peek-a-boo!  I am working on the inside of the barn stuffing cracks in the wall with a cob mixture (sand, clay, straw, little bit of water) to prevent any thermal breaks.

Look at this beautifully plastered wall!  After stacking the bales and stuffing all the cracks tightly, our bales were well prepped to receive their clay plaster coating.  We first sprayed down the entire bale wall with a super fine clay slip to give our plaster coat a little something extra to stick too.  The plaster is made up of clay, water, sand, and straw, and applied by hand to the entire wall in a slap and smear technique.  

In summary, natural wall systems are fairly similar to mexican food.  Same ingredients, change the proportions, and the name of the dish/wall is different.  You can see that the light straw clay wall, he cob mixture, the straw bale wall, and even the plaster are all derived from the same ingredients....que bueno!

Natural Walls - Take Two

In contrast to the labor intensive light straw clay assembly along our north wall, our south wall is made up of a wood chip and clay mixture.  After the wood chips, wood shavings, and sawdust are mixed together with a clay slip in a mortar mixer, 

they are poured into a double stud wall cavity faced with wood lath.  No tamping required!  The wood lath will later be finished with a lime/clay plaster.  While this wall took far less time to assemble, it also required more wood as a resource - not only in the insulation mix, but also for the lath.  

However, it does provide us with another example of a highly insulative natural wall system made up of what would be considered by-products form the conventional construction industry.

Natural Walls - The First Edition

Natural insulation is the name of the game for each of our wall assemblies.  The first wall we tackled is a double stud cavity wall along the north end of our barn.  Taking loose straw from our locally harvested and baled straw bales,

and clay slip (a diluted natural clay and water mixture), we mixed it all together like a vinaigrette over a salad to create a light straw clay.  Once all mixed up, we used flat wood panels as form work and stuffed our wall cavities with the light straw clay mix.  Tamping down all of the mix into the cavities proved to be very labor intensive, but a good way to work out any other of life's stresses! 

 And, it was so satisfying to remove the forms and move them up the wall (slip form), and see the section of the light straw clay stay in place.

This wall has a significant amount of moisture in it (due to the clay slip mixture), so we will be letting it dry out for a couple of weeks before applying plaster to it's surfaces.

Gimme Shelter

In preparation for our natural walls class (and after being rained on almost every day), it is time to raise the roof on this barn.  First, we laid 1x18 material (from one of the trees we milled!) above the exposed rafter tails.  This underside of the roof will be visible to the exterior, so we wanted it to  look nice.  Next, we laid 1x4 strapping along the rafters all the way up to the ridge.
Once our strapping was in place, we started hauling our corrugated metal roof panels up the slope of the structure and securing the panels to the strapping with coordinated green roofing screws (with neoprene gaskets).  
In two days we were able to install a roof that is green, albeit not a green roof.